Comfort and Design: Principles and Good Practice

COMFORT and DESIGN Principles and Good Practice

2830_C00.fm Page ii Tuesday, November 2, 2004 8:58 AM

COMFORT and DESIGN Principles and Good Practice

Peter Vink

CRC PR E S S Boca Raton London New York Washington, D.C.

Library of Congress Cataloging-in-Publication Data Vink, Peter Comfort and design: principles and good practice / edited by Peter Vink. p. cm. Includes bibliographical references and index. ISBN 0-8493-2830-6 (alk. paper) 1. Human engineering. I. Vink, P. II. Title. TA166.C59 2004 620.8'2—dc22 2004054512 Catalog record is available from the Library of Congress

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Foreword We are accustomed to the idea that our technology, our work practices, and our daily lives are changing at a sometimes frightening pace. One of the most ancient, commonplace, but important indicators of our compatibility with new developments is our notion of comfort. Comfort and discomfort are terms widely used and specifically understood, but lacking the sort of generally acceptable definitions that make them easy to account for in the design process. Discomfort is known to be a good predictor of musculoskeletal problems and is thus an obvious target for design effort, and comfort, as a competitive advantage, is becoming increasingly important in the battle for market share across a wide range of consumer and industrial products. The fact that there is no such thing as an agreed paradigm of comfort or discomfort makes design focused on improving comfort or reducing discomfort a challenging exercise. This book provides valuable insight into the issues. Examples come from Japan, the United States, Sweden, Germany, and The Netherlands and for the first time, case studies of good practice plus the latest theories on the topic are included in one book. It provides support for managers, designers, researchers, and all those who are concerned with designing products and work situations to increase comfort or reduce discomfort. This book gives me great satisfaction. In 1999, in cooperation with TNO, I initiated a new chair of Participatory Ergonomics at Delft University of Technology. Professor Peter Vink was appointed to the chair and his energy and achievements in the position are demonstrated in this book. Bill Green Emeritus Professor, Applied Ergonomics and Design, University of Canberra Former Head of Industrial Design, Delft University of Technology

Acknowledgments Alstom France

Ford United States

Arbouw The Netherlands

FOSAG The Netherlands

ASPA Kantoorinrichting The Netherlands

GTI The Netherlands

Bahco Tools Sweden

Grammer AG Germany

Bombardier Canada

Inalfa Roof Systems The Netherlands

Creative Box Inc. Japan

Interior Centre Japan

CRFiat Italy

JAFIKA Japan

Dutch Bricklayers Association The Netherlands

Kaiser AG Liechtenstein

Dutch Ministry of Home Affairs The Netherlands

Karimoku Japan

ETEC The Netherlands

Koninklijke Ahrend NV The Netherlands

Faber Electronics BV The Netherlands

Kosuga Japan

Finland Post Finland

Long Island RailRoad United States

FIOH Finland

Multina United States

Nissan Japan

TwinSeal The Netherlands

Paus GmbH Germany

Tytecker The Netherlands

Philips DAP The Netherlands

Volvo Car Corporation Sweden

RET The Netherlands

Yamatake Japan

About the author Peter Vink is head of the department of ergonomics and innovation at TNO in The Netherlands. (TNO is the Dutch acronym for The Netherlands Organization for Applied Scientific Research.) His group conducts research in product and system design that contributes to greater comfort or to a reduction of physical workload. Products that result from their research range from hand tools and seats to vehicle interiors and construction-site transport devices. Professor Vink has written more than 200 papers on these topics. He is past president of the Dutch ergonomics association. He is also a professor of industrial design of Delft University of Technology, where he teaches on participatory design principles and contributes to the overall knowledge base in the field of ergonomics.

Contributors J.C. Beckers RET, The Netherlands

S.M. Eikhout TNO Work and Employment, The Netherlands

T. Bosch TNO Work and Employment, The Netherlands

G. Fujimaki Waseda University, Japan

R.E. Bronkhorst TNO Work and Employment, The Netherlands

M.P. van der Grinten TNO Work and Employment, The Netherlands

F.K. Cheung Delft University of Technology, The Netherlands

L. Groenesteijn TNO Work and Employment, The Netherlands

R.C. Davies Lund University, Sweden

M.D. Hagedoorn-de Groot TNO Work and Employment, The Netherlands

M.C. Dekker Delft University of Technology, The Netherlands P.M.A. Desmet Delft University of Technology, The Netherlands J. van Deursen TNO Industrial Technology, The Netherlands J.H. van Dieën Vrije University, The Netherlands J.P. Djajadiningrat Eindhoven University of Technology, The Netherlands

B.J.A. van Haperen Delft University of Technology, The Netherlands A.M. de Jong Delft University of Technology, The Netherlands S. Kishi Waseda University, Japan M.A.J. Kompier University of Nijmegen, The Netherlands T. König Tytecker, The Netherlands

E.A.P. Koningsveld TNO Work and Employment, The Netherlands

K. Reijneveld TNO Work and Employment, The Netherlands

F. Krause TNO Work and Employment, The Netherlands

J.W. van Rhijn TNO Work and Employment, The Netherlands

L.F.M. Kuijt-Evers TNO Work and Employment, The Netherlands

I.A. Ruiter Delft University of Technology, The Netherlands

S.H. Lee University of Tsukuba, Japan

N. Schoenmaker TNO Work and Employment, The Netherlands

M.P. de Looze TNO Work and Employment, The Netherlands

J. Stahre Chalmers University, Sweden

R. Mitsuya Waseda University, Japan

T. Tereoka Waseda University, Japan

H.F. van der Molen Arbouw, The Netherlands

G.H. Tuinzaad TNO Industrial Technology, The Netherlands

S. Nichols University of Nottingham, United Kingdom K. Noro Waseda University, Japan D.S.C. Osinga TNO Work and Employment, The Netherlands C.J. Overbeeke Eindhoven University of Technology, The Netherlands

A.A. Visser Delft University of Technology, The Netherlands J. Visser Delft University of Technology, The Netherlands L. Vormer Delft University of Technology, The Netherlands

Abstract Comfort is increasingly important in sales of cars, hand tools, seats, earth-moving machines and airplane tickets. Discomfort is a predictor of musculoskeletal injuries and should be reduced in situations that consume a significant part of our time. However, there is no such thing as a general notion of comfort or discomfort. Therefore, the end user of a product must be involved in research on comfort. If managed correctly, this end-user involvement leads to profitable results, which is demonstrated in several cases in this book. This book supports managers, designers, and researchers in designing products and work stations to increase sales (by increasing comfort) and to reduce musculoskeletal injuries (by reducing discomfort). Both theory and good practice in regard to comfort and discomfort are described for the first time in one book. Examples come from Japan, the United States, Sweden, Germany, and The Netherlands. The reader is introduced to the latest developments in theories on comfort and which factors should be studied in order to optimize comfort in the workplace (Chapters 1, 2, and 3). The reader also benefits from the latest knowledge on how to involve participants in comfort research and set up a project (Chapter 4). In Chapters 5 through 22, eighteen cases that are described in detail illustrate how discomfort is reduced in a design process, or how comfort is improved. The costs and benefits of comfort products are discussed in Chapter 23.

Contents Theory Chapter 1 Comfort Experience...................................................................................................1 P. Vink, C.J. Overbeeke, and P.M.A. Desmet Chapter 2 Theory of Comfort...................................................................................................13 P. Vink, M.P. de Looze, and L.F.M. Kuijt-Evers Chapter 3 A Theory on Pressure Distribution and Seat Discomfort.......................................33 K. Noro, G. Fujimaki, and S. Kishi Chapter 4 Participatory Ergonomics and Comfort...................................................................41 P. Vink, S. Nichols, and R.C. Davies

Cases on Reducing Discomfort in Work Chapter 5 Discomfort and Productivity in Improved Bricklaying ..........................................55 P. Vink, A.M. de Jong, and E.A.P. Koningsveld Chapter 6 Reducing Discomfort in Work with New Products for Glaziers............................73 A.M. de Jong, H.F. van der Molen, and P. Vink Chapter 7 Reducing Discomfort in Installation Work .............................................................85 A.M. de Jong and P. Vink Chapter 8 Reducing Discomfort in Office Work .....................................................................95 P. Vink and M.A.J. Kompier

Chapter 9 Productivity and Discomfort in Manual Assembly Operations............................111 J.W. van Rhijn, M.P. de Looze, L. Groenesteijn, M.D. Hagedoorn-de Groot, P. Vink, and G.H. Tuinzaad Chapter 10 Productivity and Discomfort in Assembly Work: The Effects of an Ergonomic Workplace Adjustment at Philips DAP.................129 M.P. de Looze, J.W. van Rhijn, N. Schoenmaker, M.P. van der Grinten, and J. van Deursen

Cases on Chair Comfort Chapter 11 Comfort in Furniture at Home ..............................................................................137 T. Teraoka, R. Mitsuya, and K. Noro Chapter 12 Discomfort and Dynamics in Office Chairs..........................................................147 M.P. de Looze, P. Vink, and J.H. van Dieën Chapter 13 Designing Comfortable Passenger Seats...............................................................155 R.E. Bronkhorst and F. Krause Chapter 14 Comfort through an Emotion-Aware Office Chair ...............................................169 C.J. Overbeeke, M.P. de Looze, P. Vink, and F.K. Cheung

Cases on Hand Tool Comfort Chapter 15 Toward a Comfortable Paint Scraper ....................................................................181 S.M. Eikhout, R.E. Bronkhorst, P. Vink, and M.P. van der Grinten Chapter 16 Development of a Handheld Steel-Fixing Tool ....................................................193 J. Visser, T. König, I. Ruiter, and P. Vink Chapter 17 Comfort Effects of Participatory Design of Screwdrivers....................................207 S.M. Eikhout, P. Vink, and M.P. van der Grinten

Chapter 18 Comfortable Manual Bag Sealing.........................................................................219 M.D. Hagedoorn-de Groot, T. Bosch, S.M. Eikhout, and P. Vink

Cases on Vehicle Interior Comfort Chapter 19 Comfortable View in an Earth-Moving Machine of 2015....................................229 L. Vormer, M.C. Dekker, A.A. Visser, F. Krause, and P. Vink Chapter 20 Tram Drivers’ Comfort ..........................................................................................239 D.S.C. Osinga, P. Vink, and J.C. Becker Chapter 21 Redesign of Earth-Moving Machines: It’s Also in the Details ............................247 F. Krause, M.P. van der Grinten, K. Reijneveld, and R.E. Bronkhorst Chapter 22 Concept of a Future Nissan Car Interior ..............................................................263 B.J.A. van Haperen, P. Vink, C.J. Overbeeke, J.P. Djajadiningrat, and S.H. Lee

Cost/Benefits Chapter 23 Costs and Benefits of Comfort Products for Professional Use ............................281 E.A.P. Koningsveld Index......................................................................................................................289

1 Comfort Experience P. Vink, C.J. Overbeeke, and P.M.A. Desmet CONTENTS 1.1 Importance of Comfort ....................................................................................1 1.2 Importance of Discomfort................................................................................1 1.3 Striving for (Dis)Comfort ................................................................................2 1.4 Comfort Knowledge Is Needed .......................................................................3 1.5 Aspects of Comfort in an Airplane .................................................................4 1.6 Aspects of Comfort in the Literature ..............................................................5 1.7 Aspects of Discomfort in the Literature..........................................................7 1.8 Comfort Is for Everyone..................................................................................8 1.9 Comfort and Ergonomics.................................................................................8 1.10 Comfort and Emotion ......................................................................................9 1.11 Conclusions ....................................................................................................11 References................................................................................................................11

1.1 IMPORTANCE OF COMFORT Everyone pays attention to comfort. When buying a bed or a car, or flying across the ocean, comfort comes into play. Therefore, manufacturers of products such as seats, cars, beds, hand tools, and production lines strive for comfortable products in order to stay ahead of competition. Comfort is influenced by many factors in the environment. That means that it is not easy to design, market, or manage with a focus on comfort. However, knowledge about comfort is a requisite when designing an airplane interior, working in the marketing department of a hand tool manufacturer, managing the optimal performance of office workers, or trying to measure discomfort as a precursor of back complaints.

1.2 IMPORTANCE OF DISCOMFORT Reducing discomfort — another issue discussed in this book — is not a luxury. To stimulate optimal human performance, discomfort should be prevented. The tram cabin should in fact be built around the driver in order to accommodate his performance. The same applies to the environment of the assembly worker and to the software system of the office worker. Optimal human performance is needed to stay ahead of competitors, and reducing discomfort can be a great help in this regard. 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

1

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Comfort and Design: Principles and Good Practice 40%

30%

20%

10%

0% back

legs

arms

neck/shoulder

FIGURE 1.1 Percentage of workers in the EU having pain in the back, legs, arms, or neck and shoulder during more than 25% of the working time, based on 1000 workers in each EU country (Merllié and Paoli 2000).

Also, discomfort is a precursor of complaints in the back, neck, and arm and should also be prevented for that reason. Discomfort can lead to musculoskeletal problems (Proper et al. 1999) that cost society a lot of money. In a longitudinal study where 1789 subjects were followed for 4 years, a high score on postural muscular discomfort resulted in a significantly higher percentage of sick leave due to musculoskeletal injuries such as back and neck pain. This is a serious problem in Europe (Fig. 1.1), which makes preventing discomfort very important.

1.3

STRIVING FOR (DIS)COMFORT

However, at least three problems face us in striving for comfort: • • •

The exact cause of discomfort or comfort is unknown. There is no model available that describes the cause of comfort. Every individual has his or her own meaning for comfort. Comfort is a subjective phenomenon. The comfort design process is not described, and the approach is unknown.

These three problems that will be discussed in this book are interwoven, but for clarity the model, the subjective experience, and the approach are separated. The model and the subjective experience will be described in Chapter 2 and the approach in Chapter 4. Chapter 3 describes a theory on sitting comfort. The theory explained in Chapters 1 through 4 will be applied to actual cases in Chapters 5 through 22. Chapter 23 concerns costs and benefits. The present chapter describes aspects related to comfort and the way it is linked to other fields of study and applications.

Comfort Experience

1.4

3

COMFORT KNOWLEDGE IS NEEDED

There are of course manufacturers who claim that their product increases comfort because they say that they have a special sensor for that or because an expert looked at it. Of course to some degree everyone has some knowledge of comfort that can be generalized, and some predictions can be made. However, for professional situations or in buying beds (which are used about one-third of our lives) it is not wise to base it just on beliefs. Discomfort in an earth-moving machine or along an assembly line could lead to mistakes or back complaints. A lower level of comfort in an airplane could result in fewer bookings because nowadays various data for comfort ratings are easily obtainable on the Internet (Table 1.1). Therefore, design approaches involving experiments with the real end users are preferable. This is not simple, however. Just asking end users “Do you think it will be comfortable?” or “Is it comfortable when you use it?” won’t give enough input for a design. In this book, several methods are used to link the comfort experience with the design. Many studies show the positive effects of a design process in which end users play an important role (see Chapters 5 to 22). Two of these studies are • •

An approach including user tests that led to a more comfortable paint scraper (see Chapter 15), which resulted in higher sales ratios An improved assembly line (see Chapter 9) that led to higher productivity and more satisfied workers

TABLE 1.1 Example of an Internet Seat Comfort Rating of Airliners Airliner Finnair Singapore Airlines British Airways Austrian Airlines Malaysia Airlines Cathay Pacific Continental Airlines Delta Airlines South African Airways Air France Iberia KLM United Airlines US Airways Lufthansa

Seat comfort rating 8.2 8.2 7.5 7.2 7.0 6.9 6.8 6.8 6.8 6.7 6.7 6.6 6.6 6.5 6.3

Source: www.vliegtarieven.nl (August 2003).

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Comfort and Design: Principles and Good Practice

1.5

ASPECTS OF COMFORT IN AN AIRPLANE

Comfort or discomfort is often noticed during a long-distance flight in economy class (Fig.1.2). Many aspects of discomfort and comfort play a role during the flight. •

•

• •

•

Thermal comfort. One could experience dry air, cold feet, or a draft. This not only influences skin temperature, but could also result in experienced discomfort in the respiratory system. Acoustic comfort. Noise could cause some inconvenience. However, a lot has been done to reduce acoustic discomfort in airplanes. Better materials that deaden the noise, or even active antinoise systems, have been applied. Visual comfort. Sometimes the screens are of poor quality, resulting in visual discomfort. Physical comfort. Restricted leg space, the position of the screens, and reduced movement possibilities could result in back and neck discomfort, but also in problems such as deep vein thrombosis. Discomfort due to vibrations and shocks does not often play a major role during a flight, but it could be experienced as well.

FIGURE 1.2 In airplanes the hip–knee space often results in discomfort.

Comfort Experience

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Apart from the influence of the environment, our perception also plays an important role (Fig. 1.3). The way we perceive the environment is influenced by our history and mood. We could experience this flight more comfortably because it is better than previous flights, or we could experience a comfortable flight because the care provided by the flight attendant puts us in a good mood.

1.6

ASPECTS OF COMFORT IN THE LITERATURE

The above-mentioned aspects of comfort are also described in the scientific literature. The MEDLINE database lists 261 papers with comfort in the title between April 1993 and April 2003. By far most of these (140 out of 261) concern climate or thermal comfort (Fig. 1.4), which means that this is an often-studied area. An aspect of comfort not mentioned in the example of the airplane is comfort related to the treatment of sick persons. Measurements of the effects of medicine or nursing (pain/patient comfort) are seen in these papers. Research on this aspect is mentioned in 28 out of the 261 papers. The third most often mentioned issue is physical comfort (28 out of 261 papers). It concerns research regarding seating, posture, physical loading, and foot pressure measurements. Only six studies mention more than one aspect (within the others category of Fig. 1.4), so most of the studies are monodisciplinary.

FIGURE 1.3 Emotional aspects do play a role in the comfort experience and are not forgotten in the exterior design of this plane.

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Comfort and Design: Principles and Good Practice

thermal comfort acoustic comfort vibrations/shock visual comfort physical comfort perception pain/patient comfort others 0

20

40

60

80

100

120

140

160

FIGURE 1.4 Aspects of comfort mentioned in the titles of 261 scientific papers (database Medline, Applied Ergonomics).

Another search in the Swetsline database for the word comfort in a title resulted in 44 papers (Fig. 1.5) published between April 1993 and April 2003. Again, thermal comfort is most often mentioned, but so are vibration and shock. Acoustic comfort and physical comfort are third and fourth, respectively.

thermal comfort

acoustic comfort

vibrations/shock

visual comfort

physical comfort

perception 0

2

4

6

8

10

12

14

FIGURE 1.5 Aspects of comfort mentioned in the titles of 44 scientific papers (database Swetsline, Ergonomics).

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ASPECTS OF DISCOMFORT IN THE LITERATURE

Several aspects of discomfort are also found in the scientific literature. Between April 1993 and April 2003, 109 papers with discomfort in the title are listed in the MEDLINE database. Most of these papers concern pain studies (43 out of 109) and musculoskeletal aspects of physical discomfort (35 out of 109). These 35 studies concern the effects of postures or assembly tasks on musculoskeletal discomfort, but they also discuss pressure during seating (Fig. 1.6). It is interesting to note that comfort is mentioned more in climatic studies or studies regarding thermal comfort, whereas discomfort is mentioned more in the titles of studies regarding pain and musculoskeletal loading. To some extent this relationship is also found in the research among nonexperts. Chapter 2 refers to a study by Zhang et al. (1996) in which discomfort is related to clustered descriptors such as fatigue, restlessness, pain/biomechanics, strain, and circulation. Comfort is more related to clustered descriptors such as impression and relaxation. Recent research (Kuijt-Evers et al. 2004) showed that the important aspects for the end user differ according to the product. For handheld tools, functionality and reliability are important aspects closely related to comfort (Kuijt-Evers et al. 2004), while in seats comfort is strongly related to the terms relaxed, at ease, and happy (Zhang et al. 1996). Because of the fact that knowledge is available on the experience of comfort related to handheld tools, seats, vehicle interiors, and work stations, these four areas are described separately in this book. A description of the theory and examples are given for each area. Chapters 1, 2, 3, and 4 describe the theory, and Chapters 5 to 10 discuss the reduction of discomfort in work. Chapters 11 to 14 concern comfort in seat design,

thermal discomfort acoustic discomfort vibrations/shock visual discomfort physical discomfort perception pain/patient discomfort others 0

10

20

30

40

50

FIGURE 1.6 Aspects of discomfort mentioned in the titles of 109 scientific papers (database Medline, Applied Ergonomics).

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Comfort and Design: Principles and Good Practice

Chapters 15 to 18 in handheld tool design, and Chapters 19 to 22 in vehicle interiors.

1.8

COMFORT IS FOR EVERYONE

Everyone has an opinion about comfort. After reading this text, some readers will experience discomfort due to the lack of lumbar support in their chair. Others will feel incredibly comfortable and enjoy the fascinating text in combination with the excellent figures. It is difficult to predict if someone will experience discomfort, or comfort, or nothing at all. This book views comfort as a subjective phenomenon; the comfort of a product can be evaluated only by the user. A product in itself can never be comfortable. That is why this book pays much attention to how a user should be involved in the design process. The end user should be involved because he is the expert on his task and work. This end-user involvement is studied in the area of participatory ergonomics (see Chapter 4). With the help of participatory ergonomics, the design process can be structured with special attention on how to take the participants into account, especially the end user.

1.9 COMFORT AND ERGONOMICS There is a strong connection between ergonomics and comfort. Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well being and overall system performance. www.iea.cc/ergonomics (December 2003)

In fact, ergonomics is the discipline that studies how the environment should be adapted to strive for optimal human performance. One of the outcomes of an ergonomic design is comfort, or reducing discomfort. Accordingly, ergonomics is the discipline that is crucial in optimizing the environment to arrive at an experience of comfort. Therefore, much of the knowledge in this book overlaps with ergonomics. One difference between comfort and ergonomics could be that in comfort more attention is paid to the experience of the end user and to affective behavior. However, attention to experience and affective human behavior is also growing among ergonomists, which is proven, for instance, by a conference organized by ergonomists on this subject (Helander et al. 2001). Dul and Kahmann (2001) state that it is not expected that many ergonomists will become specialists in emotional experience. As a consequence of the statement mentioned above, that the comfort of a product can be evaluated only by the user, much attention should be paid to how a user should be involved in the design process. As noted earlier, this end-user involvement is dealt with in the area of participatory ergonomics — the adaptation of the environment to the human (that is, ergonomics) together with the proper persons in question (participants) (Vink 2002).

Comfort Experience

9

1.10 COMFORT AND EMOTION Given the fact that the concept of comfort has an experiential component, it can be considered to be related to our emotions. In recent years, the design community has shown a growing interest in these emotions. Because comfort is also influenced by the state we are in, it has a relationship with emotions. Kansei engineering is one method used to incorporate and study human emotions in an early stage of the design process. One of the founders of the method is Nagamachi (1998) from Japan. Kansei is a Japanese concept and difficult to translate into one word. It has to do with the human emotions. In an example of Kansei engineering, designs of parts of the vehicle interior of a Mazda were shown on a computer screen to future users (Nagamachi 1998). The users attributed words to what they saw in various designs. Speed indicators were shown in various designs: round, long, with gothic numbers, and so on. In this way the emotions of car drivers, measured as reactions on speed indicators in the dashboard, could be recorded and used as input in the design. Using Kansei engineering, data were also gathered on reactions to beer cans (Ishihara 1998). A group of 16-year-old women that had never drunk beer before could describe the taste. A similar but opposite study was performed by Smets and Overbeeke (1995). Students of industrial design were asked to design 3D models of bottles for energy drinks. The emotion caused by the taste was to be expressed in the bottle design. The drinks were tasted and based on the taste, the bottles were designed. These bottles were shown to naïve subjects, which means that the subjects did not know which taste was coupled with which bottle. The subjects were asked to match the bottles and tastes, and the accuracy of matching appeared to be very high. This means that it is possible to incorporate emotion experiments into the early stages of the design process. For the development of comfortable products it could be wise to have some knowledge of emotion and design. The emotional content of design is also important in a work setting. Manufacturers of professional products and machines anticipate this trend, which was also featured in a conference on affective human factors design (Helander et al. 2001). Researchers at the Delft University of Technology aim to develop approaches and instruments that offer designers handles for discussing the emotional impact of the product design with the intended users. Desmet et al. (2001), for example, developed the emocard method, a nonverbal self-report instrument. It was developed because Desmet and Hekkert (1998) found that emotions are difficult to verbalize, especially the type of subtle, low-intensity emotions elicited by products. Furthermore, asking users to describe their emotional responses requires cognitive involvement, which may influence the responses themselves. Therefore, the emocard method was designed to enable users to express their emotional responses without the use of words. The instrument consists of 16 emocards that depict cartoon faces with 8 distinct emotion expressions on 8 male faces and 8 female faces. These expressions vary within the dimensions of pleasantness and arousal. With these two dimensions

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Comfort and Design: Principles and Good Practice

FIGURE 1.7 The 16 emocards developed by Desmet et al. (2001) that support finding emotional reactions to products.

Russell (1980) created a “circumplex of emotions,” which was used as a visual structure for the set of emocards (Fig. 1.7). In a discussion, the emocards help the participants to express their emotional responses. For instance, participants can select a card that best expresses their emotional responses to a product. Participants can also put the cards in order of relevancy. In this way, the cards can be used both as an aid to objectify emotional responses and as an aid for starting a conversation on these responses with a designer or researcher. Recently, Desmet (2003) developed a new nonverbal self-report instrument that measures a set of 14 distinct emotions: the Product Emotion Measurement instrument (PrEmo) (Fig. 1.8). Each emotion in this set is portrayed by an animated cartoon character employing dynamic facial, bodily, and vocal expression and is presented on a computer interface. Participants can report their responses by selecting those animations that correspond with their felt emotion(s). The unique strength of PrEmo is that it combines two qualities: it measures distinct emotions and it can be used cross-culturally because it does not ask respondents to verbalize their emotions. In addition, it can be used to measure mixed emotions, that is, more than one emotion experienced simultaneously. Instruments such as emocards and PrEmo are not only worthwhile for product design, but they can also be used by management and employees in participatory workstation optimization.

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FIGURE 1.8 PrEmo interface.

1.11 CONCLUSIONS Knowledge of comfort and discomfort is important in designing chairs, beds, hand tools, and working environments. A long-distance flight could make us aware of the different aspects of comfort. Every passenger could experience a different comfort aspect during the flight because comfort is a subjective phenomenon. The fact that it is a subjective phenomenon and the fact that various aspects influence comfort, make it difficult to study. A lot is known about the thermal aspect of comfort, an aspect that is most frequently mentioned in the literature. This book is more focused on the aspects of comfort related to product design, which is a rather new area. It is closely related to ergonomics and emotional aspects, so these issues will also be described in this book. The part of ergonomics that studies user involvement in the design process (participatory ergonomics) is especially interesting because comfort is a subjective phenomenon. Therefore, a separate chapter will be dedicated to this topic.

REFERENCES Desmet, P.M.A. (2003) “Measuring emotion; development and application of an instrument to measure emotional responses to products.” In M.A. Blythe, A.F. Monk, K. Overbeeke and P.C. Wright, eds., Funology: From Usability to Enjoyment, Dordrecht: Kluwer Academic Publishers.

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Comfort and Design: Principles and Good Practice

Desmet, P.M.A. and Hekkert, P. (1998) “Emotional reactions elicited by car design: a measurement tool for designers.” Automotive Mechatronics Design and Engineering, 31st ISATA Conference Proceedings, 237–244. Desmet, P.M.A., Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with added emotional value: development and application of an approach for research through design.” The Design Journal, 4(1): 32–47. Dul, J. and Kahmann, R. (2001) “Ergonomie in de belevingseconomie.” Tijdschrift voor Ergonomie, 26(5): 15–20. Helander, M.G., Khalid, H.M. and Ming, T. (2001) Proceedings of the International Conference on Affective Human Factors Design, Singapore, June 27–29, 2001. Ishihara, S., Ishihara, K. and Nagamachi, M. (1998) “Hierarchical kansei analysis of beer can using neural networks.” In P. Vink, E.A.P. Koningsveld and S. Dhondt, eds., Human Factors in Organizational Design and Management IV, Amsterdam: Elsevier, 421–426. Kuijt-Evers, LFM, Groenesteijn, L, Looze, MP de and Vink P. (2004) “Identifying factors of comfort in using hand tools.” Applied Ergonomics, 35(3): 453–458. Merllié, M. and Paoli, P. (2002) Working Conditions in the European Union, Dublin: European Foundation for the Improvement of Living and Working Conditions. Nagamachi, M., Sakata, Y. and Imamoto, Y. (1998) “Virtual kansei engineering applied in house designing.” In P. Vink, E.A.P. Koningsveld and S. Dhondt, eds., Human factors in Organizational Design and Management IV, Amsterdam: Elsevier, 399–404. Proper, K.I., Bongers, P.M. and Grinten, M.P. van der (1999) Longitudinaal onderzoek naar rug-, nek- en schouderklachten. Deelrapport 5: Lokaal ervaren ongemak. De relatie met en de voorspelling van klachten aan het bewegingsapparaat, Hoofddorp: TNO Arbeid. Russell, J.A. (1980) “A circumplex model of affect.” Journal of Personality and Social Psychology, 39(6): 1161–1178. Smets, G.J.F. and Overbeeke, C.J. (1995) “Expressing tastes in packages.” Design Studies, 16: 349–365. Vink, P. (2002) Comfort, Delft: Delft University of Technology (inaugural address). Zhang, L., Helander, M.G. and Drury, C.G. (1996) “Identifying factors of comfort and discomfort in sitting.” Human Factors, 38(3): 377–389.

2 Theory of Comfort P. Vink, M.P. de Looze, and L.F.M. Kuijt-Evers CONTENTS 2.1 2.2

Introduction ....................................................................................................13 General Theory...............................................................................................14 2.2.1 Comfort in Dictionaries...................................................................14 2.2.2 Comfort in the Scientific Literature ................................................14 2.2.3 Comfort Is a Subjective Phenomenon.............................................14 2.2.4 The Comfort Model.........................................................................15 2.2.5 Elements of the Comfort Model .....................................................16 2.3 Theory per Product ........................................................................................19 2.3.1 Preventing Discomfort at Work.......................................................19 2.3.2 Factors Influencing the Comfort Experience ..................................20 2.3.2.1 Theory of Herzberg...........................................................20 2.3.3 Theory of Seat Comfort ..................................................................20 2.3.3.1 Chair Elements’ Relative Contribution to Comfort and Discomfort..................................................................23 2.3.4 Theory of Hand Tool Comfort ........................................................23 2.3.5 Theory of Vehicle Interior Comfort ................................................24 2.3.5.1 Comfort Aspects in Earth-Moving Machines...................26 2.3.5.2 Scientific Knowledge about Vehicle Interiors ..................26 2.3.5.3 A Study to Find Out End-User Opinions.........................27 2.3.5.3.1 Current Machine ..............................................29 2.3.5.3.2 Improvement Possibilities................................29 2.4 Conclusions ....................................................................................................30 Acknowledgment .....................................................................................................30 References................................................................................................................30

2.1 INTRODUCTION In Chapter 1 it was shown why knowledge of comfort is important. This knowledge could support the design of products such as seats, vehicles, and hand tools and increase sales, but it could also help prevent injuries of the back, shoulders, and arms. In this chapter the knowledge available in the literature on comfort related to seat, hand tool and vehicle interior design is described. The first sections concern the general theory, including an overview of what is under debate in the literature

0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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Comfort and Design: Principles and Good Practice

and on the consensus found in research. After that a model is described, followed by the theory applied to products related to sitting, hand tools, and vehicle interiors.

2.2 2.2.1

COMFORT

IN

GENERAL THEORY

DICTIONARIES

The meaning of the word comfort differs among different dictionaries and in different countries. It is described as “freedom from pain; well being” in most dictionaries (e.g., the New Penguin English Dictionary 2000; Van Dale 2000). In these dictionaries, comfort is also translated as “convenience of the interior, or things which bring bodily ease.” Many people probably associate comfort with the interior or with visible things such as footwear and clothing. However, comfort research is also focused on climate (Chapter 1), and in several languages you can be ahead of your competitor and have a comfortable advantage. In this case, comfortable means that you don’t have to worry so much. So it seems that the interior is not the only area of comfort research.

2.2.2

COMFORT

IN THE

SCIENTIFIC LITERATURE

In the scientific literature the definition of comfort is under debate. Slater (1985) defines comfort as a pleasant state of physiological, psychological, and physical harmony between a human being and his or her environment. Richards (1980) stresses that comfort is the state of a person that involves a sense of subjective wellbeing, in reaction to an environment or situation. Regarding discomfort, mostly medical patients or physical discomforts are mentioned. Discomfort scales are also often used in biomechanical or musculoskeletal research (Marras 2003). It is assumed that more local discomfort (sometimes described as local postural discomfort) means a higher loading and a higher chance of getting musculoskeletal injuries. Despite the ongoing debate on the meaning of comfort, there are some issues that are generally accepted (Looze et al. 2003): • • •

2.2.3

Comfort is a construct of a subjectively defined personal nature. Comfort is affected by various factors (physical, physiological, psychological). Comfort is a reaction to the environment.

COMFORT IS

A

SUBJECTIVE PHENOMENON

So, these three points are not under debate. One of them — comfort is a subjective experience — is of special importance because it strongly relates to how to cope with comfort in design. A product in itself can never be comfortable; it becomes comfortable (or not) in its use. The user decides whether or not a product is comfortable, or leads to discomfort, by using the product. This complicates the construct of comfort because it is not known how every individual will react to a product. For instance, for Passenger 1 on a long-distance flight, back discomfort is of great importance. Passenger 2 wants a reduction in noise and Passenger 3 needs more space. This complication is one of the reasons why designing comfortable products is difficult.

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15

FIGURE 2.1 An experiment establishing discomfort and comfort in the design phase of a train interior (Bronkhorst and Krause 2002).

However, it is not impossible to design comfortable products such as a train interior. Recently, a train interior was designed that was described as comfortable by 83% of the passengers (Bronkhorst and Krause 2002; see also Chapter 13). During the design of the interior, experiments were performed in a setting that was as naturalistic as possible to find the optimum comfort experienced by end users (Fig. 2.1). In this book, comfort is defined as convenience experienced by the end user during or just after working with the product. The product can be a building, a means of conveyance, a utility article, a work station, clothing, or furniture.

2.2.4

THE COMFORT MODEL

Comfort could have three manifestations: • • •

Discomfort. The participant experiences discomfort because of physical disturbances in the environment. No discomfort. The participant is not aware of discomfort or comfort, or there is no discomfort. Comfort. The participant experiences noticeably more comfort than expected and feels comfortable.

The comfort model is shown in Fig. 2.2. It is a simplification of a more detailed model developed by Looze et al. (2003). The output is located on the right side of the model: comfort, no discomfort, and discomfort. The experience of discomfort or comfort is partly due to ourselves: (1) the history of our comfort experiences determines our expectations of a product, based on what we are used to; and (2) our state could be excited or relaxed, which influences our mood and thereby our continuing state. And of course all of this takes place in a certain environment. The experience of comfort and discomfort is also caused by external stimuli (input). The inputs are shown on the left side of the figure. For example, our sensors receive the pressure and after this input the selection and weighing processes start.

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Comfort and Design: Principles and Good Practice

Environment history + state

visual input smell

comfort

noise no discomfort

temperature/ humidity pressure/touch

discomfort

posture/movement

FIGURE 2.2 The comfort model. The feeling of (dis)comfort is determined by the input recorded by sensors and the information processing that is influenced by the history and state of the participant.

Our state of arousal or experiences in the past influence these weighing processes. Based on these processes, the product causes comfort, discomfort, or nothing that we are aware of. The output is also influenced by the environment, in which case the input is noticed in our mind. This is an important factor and it is unknown how the environment influences the comfort experience. A consequence is that a product should always be tested in an environment that is as close to reality as possible.

2.2.5

ELEMENTS

OF THE

COMFORT MODEL

In this section each element of the model is described separately, but in reality these elements are not separated. It is not known how the elements are related to each other and what the contribution of each element is to the total experience. That is why it is important to analyze the user situation (e.g., during a task analysis) and to perform experiments with products in the design phase in an environment as close to the naturalistic setting as possible. 1. History influences the experience. This is important for product designers. Products should have at least the level of comfort people are used to. A nonadjustable office seat will be experienced as not comfortable in western European countries such as Sweden and the Netherlands. A caveman would not have this problem (although the opinion of the caveman is now difficult to verify in an experiment). We always evaluate the appearance and styling of a product with our past as a reference. That means that a product designer should know the history and social behavior of the target group. Drivers of earth-moving machines are used to the

Theory of Comfort

17

FIGURE 2.3 The comfort experienced in the interior of an earth-moving machine (A) is influenced by the previous experiences in car (B).

comfort of their personal automobiles. They expect a comparable level of comfort in the vehicle interior of their earth-moving machine (Fig. 2.3). 2. Our state also influences whether we experience discomfort or comfort. After a few hours of heavy physical exercise, a relaxed seat is more comfortable than after sitting for 3 hours in a car. Picard (1997) showed in her research that emotions, feelings, and mood play a role in the way someone evaluates a product. A mock-up in a clean laboratory may receive a different evaluation than a mock-up evaluated on the shop floor. The environment or situation, therefore, influences the state of people. 3. The visual input also influences our experiences. Visual information plays a major role; it is the first impression of comfort. In the design world, visual information is important. The first ideas of a product are often communicated visually (Lugt 2001), and later on in the design process drawings (Fig. 2.4) or computer pictures are also

FIGURE 2.4 Drawings used in discussions with users: (A) design De Groot, TNO; (B) design Cheung, TU-Delft.

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Comfort and Design: Principles and Good Practice

FIGURE 2.5 Example of a picture made by a computer and used in discussions with users to design the work stations.

used (Fig. 2.5). It is important to realize that comfort is not influenced by styling or appearance alone. Kuijt-Evers (in Bronkhorst et al. 2001) showed that 49 experienced office workers evaluated 1 out of 4 office chairs negatively based on the visual information (a brown traditional chair). Contrary to what was expected, this chair was evaluated positively after actually using it. 4. The sense of smell also has an influence. Different authors (e.g., Theimer 1982) report that smell influences our experiences, and mostly we are not aware of this effect. It even influences our sexual activity, aggression, and territorial behavior. In some ways we all know that: when your neighbor is flatulent, you involuntarily move your body to the other side to avoid the smell. As with other inputs, every person will react differently to the smell associated with a product. Most people like the scent of a new car, but some do not. 5. Noise is a type of input that can influence comfort positively or influence discomfort negatively. The noise of the engine while working in an earth-moving machine can lead to discomfort (Vink et al. 2001), whereas the sound of a HarleyDavidson is a kind of music to some of us. 6. Temperature and humidity are also related to (dis)comfort. Searching for comfort on the Internet leads you mostly to temperature and climate issues. Air conditioning, office temperature, drafts, and humidity are often associated with comfort. A pleasant climate is often not noticed, but a high or low temperature attracts attention and the discomfort is perceived. According to Carrier, one of the largest manufacturers of indoor air-quality systems, indoor air quality is the most important reason why office rental contracts are not extended (www.carrier.com, June 2001). This is certainly not an objective source, but it indicates that the issue has some importance.

Theory of Comfort

19

7. Various studies show the relationship between pressure and discomfort in sitting (Goossens et al. 1998, 2002). Goossens (1998) increased the force applied to a buttock by a circle 30 mm in diameter. He found a clear correlation between the level of pressure (force increase) and the perceived discomfort. To feel pressure we have sensors located in the skin. Generally, a better distribution of pressure between a seat or handle and the human body leads to less discomfort. A literature survey (Looze et al. 2003) showed that of all objective measures, the distribution of pressure has the clearest relationship to discomfort in sitting. In this area Goossens et al. (2002) have done some impressive work. They showed that participants are able to perceive small differences in pressure on their bottoms and could translate this to discomfort. In addition to pressure we also have touch. A thick carpet is experienced as different from a concrete floor by our bare feet, and the textures of handles have an influence on the feeling of comfort. Sonneveld (2002) describes how we can take these feelings into account during the design process. 8. The posture and movements determined by the product can also lead to discomfort. In the long run, local perceived discomfort could even result in musculoskeletal disorders (Proper et al. 1999; see also Chapter 1). Back pain is found in onethird of all European workers. Neck and shoulder pain is found in almost one-quarter of European workers. Not only is the human factor a problem, but also the costs. In the Netherlands, musculoskeletal injuries cost €8 billion each year (Bongers et al. 2000). Thus, the problem is large enough to require that something should be done about it. This is an opportunity for designers: design products that reduce musculoskeletal injuries. In other words, use experiments during the design process to avoid discomfort and as a result prevent musculoskeletal injuries. In designing a product, all sensory modalities should be considered. This could be a lot of work. Therefore, it is often wise to think about the use of the product and to derive the sensors that have priority. Recently, at Delft University of Technology, a study was done to assess each modality’s potential contribution to overall product experiences (Schifferstein and Cleiren 2004). An approach was used in which subjects experienced real-life products through one modality: either vision, touch, audition, or olfaction (smell). Visual and tactual information appeared to be most detailed and resulted in the clearest memories of past events and associations with other products. Because vision may have an advantage over touch by virtue of the speed with which visual information is processed, vision is likely to dominate product experiences in real-life situations (Schifferstein and Cleiren 2004).

2.3 THEORY PER PRODUCT 2.3.1

PREVENTING DISCOMFORT

AT

WORK

To stimulate optimal human performance, discomfort should be prevented. An assembly work station should, in fact, be built around the operator to accommodate his performance. The same applies to the software system of the office worker. Optimal human performance is needed to stay ahead of competitors, and reducing discomfort can be of great help. Therefore, striving for discomfort reduction is very important.

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Comfort and Design: Principles and Good Practice

Musculoskeletal discomfort is often measured in a work environment (Marras 2003) in order to optimize the work station layout. Establishing the reduction of discomfort in experiments during the design process is needed to prevent musculoskeletal injuries. A method often used to study discomfort is the LPD (local postural discomfort) method. The way this method can be applied to optimize work stations will be discussed in Chapters 8, 13, and 15.

2.3.2

FACTORS INFLUENCING

THE

COMFORT EXPERIENCE

The way comfort, discomfort, and no comfort are related differs according to the type of product, but the factors influencing comfort also differ. In this section the factors influencing comfort are described for seats, hand tools, and vehicle interiors. The motivation theory of Herzberg et al. (1993) is described first because of its similarity to this framework discussed here. 2.3.2.1

Theory of Herzberg

In the late 1950s, Herzberg was considered by many to be a pioneer in motivation theory. He interviewed employees to find out what made them satisfied and dissatisfied on the job. Physical factors, according to Herzberg, cannot motivate employees, but they can minimize dissatisfaction if handled properly. In other words, they can only dissatisfy if they are not all right. Dissatisfaction is related to company policies and salary (Table 2.1). Motivators, on the other hand, create satisfaction by fulfilling individuals’ needs for meaning and personal growth. These are issues such as the work itself and advancement, and they are related to satisfaction. TABLE 2.1 Factors Influencing Satisfaction or Dissatisfaction Dissatisfaction - Company policies - Administrative procedures - Salary - Working conditions

Satisfaction - The work itself - Achievement - Recognition - Advancement

Based on Herzberg et al. (1993).

2.3.3

THEORY

OF

SEAT COMFORT

In the areas of comfort and discomfort a similar division can be made. If we consider comfort and discomfort during sitting, absence of discomfort does not automatically result in comfort. Comfort will be felt when more is experienced than expected. This is supported in research by Zhang et al. (1996) and by Helander and Zhang (1997). Based on questionnaires, they found that discomfort is more related to pain, ache, and heavy legs (Table 2.2). When there is absence of discomfort, nothing is experienced. To notice comfort, more should be experienced. Comfort is related to a sense of well-being and to the plushness of the chair.

Theory of Comfort

21

TABLE 2.2 Factors Influencing Comfort or Discomfort during Sitting Pain Sore Ache Circulation to legs cut off Hurting Dull ache Swollen ankle Numb Stiff Heavy legs

Discomfort* 0.81 0.81 0.81 0.79 0.79 0.78 0.76 0.71 0.71 0.68

Relaxed At ease Happy Content Pleased Pleasant Well-being Restful Safe Calm

Comfort* 0.82 0.82 0.81 0.81 0.81 0.79 0.76 0.76 0.73 0.73

*The factor loading after varimax rotation. (The higher the number, the better the relationship to discomfort or comfort.) Based on Zhang et al. (1996).

Zhang et al. (1996) did cluster the descriptors. Discomfort is related to clustered descriptors such as fatigue, restlessness, pain/biomechanics, strain, and circulation. Comfort is more related to impression, relief/energy, well-being, and relaxation (Table 2.3). Looze et al. (2003) described a more refined theoretical model based on the aforementioned findings of Zhang et al. (1996). In this model (Fig. 2.6) different factors underlying sitting discomfort and comfort are described, as well as the relationships between these factors. Also, discomfort and comfort are seen as separate entities in this model. The left part of this theoretical model concerns discomfort. The physical processes underlie discomfort, agreeing with comparable models on the etiology of work-related physical complaints (Winkel and Westgaard 1992; Armstrong et al. 1993). These authors consider exposure, dose, response, and capacity as the main issues. According to Armstrong, exposure refers to the external factors producing a disturbance of the internal state (dose) of an individual. The dose may evoke a TABLE 2.3 Cluster of Factors Influencing Comfort or Discomfort during Sitting Discomfort - Fatigue - Restlessness - Pain/biomechanics - Strains - Circulation Based on Zhang et al. (1996).

Comfort - Impression - Relief/energy - Well-being - Relaxation

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Comfort and Design: Principles and Good Practice

COMFORT MODEL

Human

physical capacity

SITTING DISCOMFORT (= feelings of pain, soreness, numbness, stiffness)

Product

physical features

Context

physical processes

SITTING COMFORT (= feelings of relaxation, well-being)

expectations

emotions

physical features aesthetic design physical environment task

physical environment task psychosocial factors

FIGURE 2.6 The comfort model for sitting described by De Looze et al. (2003).

cascade of mechanical, biochemical, or physiological responses. The extent to which external exposure leads to an internal dose and responses depends on the physical capacity of the individual. With regard to sitting, it could be said that the physical characteristics of the office seat (product level, e.g., form, softness), the environment (context level, e.g., table height), and the task (context level, e.g., the performance of VDU activities) expose a seated person to loading factors that may involve forces and pressure from the seat on the body and joint angles. These external loads may yield an internal dose in terms of muscle activation, internal force, intradisc pressure, nerve and circulation inclusion, and skin and body temperature rise, provoking further chemical, physiological, and biomechanical responses. The perception of discomfort may be established by exterocepsis (stimuli from skin sensors), propriocepsis (stimuli from sensors in the muscle spindle, tendons, and joints), interocepsis (stimuli from internal organ systems), and nocicepsis (stimuli from pain sensors). The right part of the model concerns comfort, that is, feelings of relaxation and well-being. Again, the influential factors are presented on human, seat, and context levels. At the context level, not only the physical features are assumed to play a role, but also psychosocial factors such as job satisfaction and social support. At the seat level, the aesthetic design of a seat in addition to its physical features may affect the feelings of comfort. At the human level, the influential factors are assumed to be individual expectations and other individual feelings or emotions. The dominant factor of discomfort, as suggested by Helander and Zhang (1997), is illustrated by the horizontal arrows pointing from the left (discomfort) to the right (comfort) part of the model.

Theory of Comfort

23

TABLE 2.4 The Statements Used in the Chair Evaluation Checklist Discomfort statements -I have sore muscles -I have heavy legs -I feel uneven pressure -I feel stiff -I feel restless -I feel tired -I feel uncomfortable

Comfort statements -I feel relaxed -I feel fit -The chair feels soft -The chair is spacious -The seat looks nice -I like the chair -I feel comfortable

The 79 office workers gave their ratings for each statement on a 9-point scale (1 = I complete disagree; 9 = I completely agree). From Helander and Zhang (1997).

2.3.3.1

Chair Elements’ Relative Contribution to Comfort and Discomfort

In designing a chair it is important to know what elements of the chair are major factors determining the level of discomfort and comfort. In an unpublished study of 15 contemporary office chairs by Looze, the levels of comfort and discomfort were measured by use of the chair evaluation checklist of Helander and Zhang (1997). This methodology is based on the theory of seat comfort mentioned earlier. On a 1-to-9 scale subjects had to rate their opinions (1 = I completely disagree; 9 = I completely agree) about 14 statements (Table 2.4) addressing the underlying factors of comfort and discomfort. The sum of the ratings yielded separate ratings for comfort and discomfort. In addition, the same subjects gave their ratings for separate chair elements. By a multiple regression analysis, we found the following regression equations: discomfort = 38,175 − 2,743 backrest uniformity − 2,431 seat pan uniformity (R 2 = 0,273) comfort = 13,158 + 3,247 backrest comfort + 2,741 seat pan uniformity + 1,442 armrest comfort (R 2 = 0,511) This indicates that the uniformity of pressure distribution on the backrest and seat pan are the main factors determining discomfort, whereas comfort is mainly determined by the comfort of the backrest and the uniformity of pressure distribution of the seat pan and, to a lesser extent, by the comfort of the armrest. Other elements such as softness of the seat, armrest material, and texture of the seat appear to be of a lesser importance.

2.3.4

THEORY

OF

HAND TOOL COMFORT

Most theories of comfort concern seating. However, comfort also plays an important role in the use of hand tools. Based on studies where users were asked to describe their experience with screwdrivers, Kuijt-Evers et al. (2004a) showed an important

24

Comfort and Design: Principles and Good Practice

difference between the construct of comfort/discomfort in using hand tools (such as screwdrivers and pliers) and comfort/discomfort in seating. In seating, comfort and discomfort are different entities with different underlying determinants. Comfort is associated with feelings of relaxation and well-being and discomfort is associated with pain, tiredness, soreness, and numbness (Zhang et al. 1996). However, in the use of hand tools adverse body effects, like cramped muscles, blisters, and inflamed skin, underlie both comfort and discomfort. Additionally, comfort is mostly determined by functionality and physical infraction using hand tools (Kuijt-Evers et al. 2004b). This could be explained by the different nature of seats and hand tools. Unlike sitting, the use of hand tools is mostly accompanied by discomfort. Helander and Zhang (1997) argue that when discomfort factors are present, comfort factors become secondary in the perception of comfort/discomfort. Because discomfort factors are present in hand tool use, comfort may be dominated by discomfort. Therefore, respondents may also think of comfort while using hand tools in terms of the absence or reduction of discomfort. These results are supported by several hand tool evaluation studies in which comfort is measured in terms of discomfort (Chao et al. 2000; Fellows and Freivalds 1991). From this perspective, comfort and discomfort in using hand tools can be seen as two opposites on a continuous scale, as supported by Vergare and Page (2000), Jianghong and Long (1994), Wilder et al. (1994), and Jensen and Bendix (1992). The factors having the closest relationship with comfort are good fit in hand, functional, easy to use, and reliable (Table 2.5). Clustering these factors is also possible. Descriptors such as good fit in hand, functional, reliable, and safe have a strong relationship with comfort in using hand tools. Descriptors such as solid design, professional looks, styling, and nice color are slightly related or not related at all to comfort. Based on statistical analysis, six comfort factors could be distinguished (functionality, posture and muscles, irritation and pain of hand and fingers, irritation of hand surface, handle characteristics, and aesthetics; see Table 2.6). These six factors explain 53.8% of the variance and can be classified into three meaningful groups: functionality, physical interaction, and appearance. We can conclude that in the use of hand tools the same descriptors are related to comfort as to discomfort; descriptors of functionality are most related to comfort, followed by descriptors of physical interaction; and descriptors of appearance become secondary in determining comfort when using hand tools.

2.3.5

THEORY

OF

VEHICLE INTERIOR COMFORT

Vehicle interiors are found, for example, in earth-moving machines, trains, streetcars, cars, and airplanes. In a vehicle, a seat and often controls (more or less related to hand tools) are found among other elements that influence comfort, such as view, climate, noise, and vibration. This complicates the decision on how to improve the comfort in a vehicle interior. The theory of comfort and discomfort in seating and in using hand tools does not give us enough support to make a decision on how an ideal comfortable interior should be designed. Based on theory, we may know how to design a comfortable seat and comfortable controls, but comfort in such a complicated

Theory of Comfort

25

TABLE 2.5 Ranking of Descriptors in the Study of Kuijt-Evers et al. (2004a)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Descriptor Good fit in hand Functional Easy in use Reliable Force exerted from tool Safe Handle feels comfortable No peak pressure on hand No blisters High-quality tool No pain Task performance No body part discomfort High product quality Lack of tactile feeling Low handgrip force supply No muscle cramp Handle shape Friction between hand and handle Comfortable working posture

Mean rating* 1.10 1.10 1.14 1.14 1.16 1.20 1.22 1.24 1.24 1.24 1.24 1.26 1.27 1.28 1.29 1.34 1.36 1.38 1.39 1.41

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Descriptor Sharpness No slippery handle Pleasurable No irritation No numbness in fingers No inflamed skin Handle size Relaxed working posture Roughness of handle surface No sore muscles Handle doesn’t feel clammy Easy to take along Weight of tool No pressure on hand No sweaty hands Handle hardness Solid design Professional looks Styling Nice color

Mean rating* 1.42 1.44 1.44 1.48 1.51 1.52 1.58 1.62 1.64 1.64 1.70 1.74 1.78 1.80 1.80 1.82 2.78 3.08 3.38 3.68

* The lowest score has the closest relationship to comfort.

environment as a vehicle interior is determined by more factors than these. Therefore, information is needed about all the aspects that influence comfort in vehicle interiors, as well as about the relationships between them. Because comfort is a subjective phenomenon, the end user plays an important role in the specification of the aspects of comfort that need improvement. The next TABLE 2.6 Cluster of Factors Influencing Comfort or Discomfort during Hand Tool Use Discomfort - Nonfunctional - Bad posture/high muscle activity - Irritation and pain in hand/fingers - Bad hand surface - Bad handle characteristics - Bad aesthetics

Comfort - Functional - Good posture/relaxed muscle activity - No irritation and pain in hand/fingers - Good hand surface - Good handle characteristics - Good aesthetics

The upper factors are of greatest importance. Based on Kuijt-Evers et al. (2004a)

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Comfort and Design: Principles and Good Practice

steering wheel cab dimensions vibration

design/ engin.

climate sales/ market.

vision noise controls seat 0

10

20

30

40

FIGURE 2.7 Attention to the comfort aspects by 80 representatives of manufacturers in the coming years.

section presents an example of how end users give their opinions on what should be improved in an earth-moving machine. 2.3.5.1

Comfort Aspects in Earth-Moving Machines

Comfort in earth-moving machines has improved dramatically in the last 4 years and is seen as an important sales argument. A study among 84 designers and marketers employed by manufacturers (Vink et al. 2003) showed that 80 of the manufacturers will pay attention to comfort during the coming years. Comfort, then, is an issue. Most priority will be given to seat improvements, followed by noise and view issues (Fig. 2.7). The attention given differs somewhat if the answers of designers and engineers are compared with the answers of sales and marketing managers. Sales and marketing focus more on noise, whereas designers and engineers give priority to seats and controls. It will be interesting to see whether the emphasis of the manufacturers really fullfils the needs of end users. Therefore, the results of this study will be compared with the operators’ needs. The conclusion is that comfort cannot be left out of the machine anymore. The automotive industry paid attention to comfort for more than 10 years, although a lot remains to be improved there, too. In fact, operators of earth-moving machines are used to comfort in their own cars and have similar demands for the interiors of their machines. 2.3.5.2

Scientific Knowledge about Vehicle Interiors

Some information is also found in the scientific literature regarding comfort in earth-moving machines. Many studies refer to vibration (Kittusamy 1999) and

Theory of Comfort

27

noise (Brambilla et al. 2001). Zimmerman et al. (1997) show that the main problems of earth-moving machinery operators concern physical complaints in the neck/shoulder and low back region, as well as general fatigue and feelings of discomfort. This might be attributed to a combination of static load during prolonged and often awkward sitting postures, exposure to whole-body vibrations, and handling and steering the machine (Zimmerman et al. 1997; Tola et al. 1988; Looze et al. 2000). A comfortable, well-designed vehicle interior may improve postures and provide an environment stimulating optimal operator performance. Based on a literature review about musculoskeletal disorders and their risk factors, Zimmerman et al. (1997) recommended four guidelines for reducing work-related musculoskeletal disorders among operators: • • • •

Minimizing the magnitude and frequency of vibration reaching the operator Optimizing the location of controls so that reach distance, trunk flexion, and rotation are minimized Providing maximum operator visibility from an upright, supported, seated posture Taking regular breaks to minimize the effects of sustained postures

Improvements in cab comfort are very often based on reducing the risk factors for work-related musculoskeletal disorders (Zimmerman 1997; Attebrant 1997). Aspects that have to be improved are mentioned in only a few studies. Nakada (1997) describes the desirability ranking defined for dump trucks and wheel loaders by a group consisting of a product creator, designers, design engineers, operators, and young people. Nakada (1997) shows that from a design perspective much attention is paid to the instrument panel monitors and meters and the operator seat. Unfortunately, the operators’ opinions cannot be distinguished in Nakada’s study (1997). In order to design a comfortable vehicle interior, the opinions of the operators are important, as they are the end users of the machines. Their experience as users may be of great help in designing a comfortable cab. Therefore, Kuijt-Evers et al. (2003) defined aspects mentioned by wheel loader and excavator operators that can be used to improve the comfort of vehicle interiors in the future. 2.3.5.3

A Study to Find Out End-User Opinions

In the study by Kuijt-Evers et al. (2003), 336 operators were interviewed at a BAUMA trade fair, the world’s largest exhibition of construction equipment. Most of the participants were wheel loader operators (n = 61) and excavator operators (n = 212). Only the results for excavator operators are presented here, as they account for 62.7% of the respondents. Figure 2.8 is an example of an excavator and a wheel loader is shown in Fig. 2.9. The interview questions considered characteristics of the population, evaluation of the current machine being operated, and future demands. Kuijt-Evers et al. (2003) assumed that if more than 20% of the operators rated a part of the machine “average” or “poor,” then comfort improvements were possible in the vehicle’s interior.

28

FIGURE 2.8 An excavator.

FIGURE 2.9 A wheel loader.

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TABLE 2.7 Aspects Rated “Average” or “Poor” by More Than 20% of the Operators for Excavators Less Than 4 Years Old Aspect Seat comfort Vibration and damping Dashboard and displays Climate control What the machine looks like Cab dimensions, interior space, ingress and egress Noise reduction View Adjustability of seat and controls Reliability

Operators (%) 29.5 27.0 26.0 24.1 24.0 22.3 21.9 21.9 21.0 20.9

2.3.5.3.1 Current Machine Among the excavators, 50% appeared to be less than 4 years old. Of the excavator operators, 55.9% rated the overall cabin comfort as “good” or “very good.” To find aspects that can increase cab comfort in the future, only the data of newer machines is analyzed. As seen in Table 2.7, several aspects of the excavators are rated “average” or “poor” by more than 20% of the operators, including seat, vibration and damping, dashboard and displays, and climate control. 2.3.5.3.2 Improvement Possibilities The operators also generated 467 ideas to improve the machine’s comfort. These aspects were classified into 15 categories, of which seat comfort, climate control, cab design (cab design, dimensions, ingress/egress), and accessories are most often mentioned (Fig. 2.10). seat comfort 21%

others 29%

climate contro 19%

accessories 12% cab design 19%

FIGURE 2.10 Categories of items most mentioned by operators to improve vehicle interior comfort.

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When the results of Kuijt-Evers et al. (2003) are compared with the results of Nakada (1997), both studies rank the operator seat high. The instrument panel, monitors, and meters are also ranked high in the study by Nakada (1997). In the study by Kuijt-Evers et al. (2003) the dashboard and displays are high on the list of parts rated as “average” or “poor” by more than 20% of the operators, but they are not seen as aspects that can improve cab comfort. Kuijt-Evers et al. (2003) also mention vibration but Nakada (1997) does not, probably because experienced operators played a larger role in the Kuijt-Evers study (2003) compared to Nakada’s subjects, and because Nakada was focused on the interior design. This study shows how information from end users can be gathered to set priorities for improving comfort among the parts of a vehicle interior.

2.4 CONCLUSIONS In this chapter the theory of comfort has been described in relation to design. Comfort/discomfort is a construct of a subjectively defined personal nature. It is affected by various kinds of factors (physical, physiological, and psychological), and it is a reaction to the environment. A theoretical model of comfort/discomfort has been proposed, based on literature review and experiments and specified for seats, hand tools, and vehicle interiors. The subjective character of comfort/ discomfort implies that the opinion of end users is needed when designing comfortable products. The study concerned with earth-moving machinery showed that end users as well as manufacturers could give important information on how to design a more comfortable product. These may help focus attention on the major aspects that need improvement in order to achieve our goal: the design of comfortable products and workplaces.

ACKNOWLEDGMENT The authors want to thank the Koninklijke Ahrend NV for supporting part of this study.

REFERENCES Armstrong, T.J., Buckle, P., Fine, L.J., Hagberg, M., Jonsson, B., Kilbom, A., Kuorinka, I.A.A., Silverstein, B.A., Sjøgaard, G. and Viikari-Juntira, E.R.A. (1993) “A conceptual model for work-related neck and upper limb disorders.” Scandinavian Journal of Work, Environment and Health, 19: 73–84. Attebrant, M., Winkel, J., Mathiassen, S.E. and Kjellberg, A. (1997) “Shoulder-arm muscle load and performance during control operation in forestry machines; effects of changing to a new armrest, lever and boom control system.” Applied Ergonomics, 18(2): 85–97. Bongers, P.M., et al. (2000) Risicofactoren voor lage rugklachten: resultaten van een longitudinaal onderzoek, Hoofddorp: TNO Arbeid. Brambilla, G., Carletti, E. and Pedrielli, F. (2001) “Perspective of the sound quality approach applied to noise control in earth-moving machines.” International Journal of Acoustics and Vibration, 6(2): 90–96.

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Bronkhorst, R.E. and Krause, F. (2002) “End-users help design mass transport seats.” In Human Factors in Seating and Automotive Telematics (SP-1670), SAE World Congress, Detroit, Michigan, March 4–7. Warrendale (PA): SAE, 1–6. SAE Technical Paper Series 2002-01-0780. Bronkhorst, R.E., Kuijt-Evers, L.F.M., Cremer, R., Rhijn, J.W. van, Krause, F., Looze, M.P. de and Rebel J. (2001) Emotie en Comfort in Cabines: Rapportage TNO Basisfinanciering 2000, Team 40, Hoofddorp: TNO Arbeid. Chao, A., Kumar, A.J., Emery, C.T.N.D., Nagarajarao, K. and You, H. (2000) “An ergonomic evaluation of cleco pliers.” Proceedings of the 14th Triennial Congress of the International Ergonomics Association, San Diego: 4–441 (on CD-ROM). Fellows, G.L. and Freivalds, A. (1991) “Ergonomics evaluation of a foam rubber grip for tool handles.” Applied Ergonomics, 22(4): 225–230. Goossens, R.H.M. (1998) “Measuring factors of discomfort in office chairs.” In P.A. Scott et al., eds., Global Ergonomics. Proceedings of the Ergonomics Conference, Amsterdam: Elsevier Science. Goossens, R.H.M., Teeuw, R. and Snijders, C.J. (2002) “Sensitivity for pressure difference on the ischial tuberosity.” Ergonomics (submitted). Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.” Ergonomics, 40: 895–915. Herzberg, F., Mausner, B. and Snyderman, B.B. (1993) The Motivation to Work, Somerset, NJ: Transaction Publishers. Jensen, C.V. and Bendix, T. (1992) “Spontaneous movements with various seated-workplace adjustments.” Clinical Biomechanics, 7: 87–90. Jianghong, Z. and Long, T. (1994) “An evaluation of comfort of a bus seat.” Applied Ergonomics, 25: 386–392. Kittusamy, K. (1999) Subjective Response to Whole-Body Vibration among Operators of Construction Equipment, Huntington, WV: Marshall University. Kuijt-Evers, L.F.M., Krause, F. and Vink, P. (2003) “Aspects to improve cabin comfort of wheel loaders and excavators according to operators.” Applied Ergonomics, 34(3): 265–272. Kuijt-Evers L.F.M., Groenesterjin, L. Looze, M.P. de, and Vink, P. (2004a) “Identifying factors of comfort in using hand tools.” Applied Ergonomics, 35(5): 453–458. Kuijt-Evers L.F.M., Twist, J. Groenesterjin, L. Looze, M.P. de, and Vink, P. (2004b) “Identifying productors of comfort and discomfort in using hand tools using the comfort questionnaire for hand tools (CQH).” Ergonomics (submitted). Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discomfort and the relationships with objective measures.” Ergonomics, 46: 985–997. Looze, M.P. de, Roetting, M., Vink, P. and Luczak, H. (2000) “Towards comfortable and efficient man–machine interaction in the cabins of vehicles.” Proceedings of the 14th Triennial Congress of the International Ergonomics Association, San Diego: 3–340 (on CD-ROM). Lugt, R. van der (2001) Sketching in Design Idea Generation Meetings, Delft: TU Delft (Proefschrift). Marras, W.S. (2003) “The future of research in understanding and controlling work-related low back disorders.” In Ergonomics in the Digital Age, Proceedings of the 15th Triennial Congress of the International Ergonomics Association, Seoul (on CDROM). Nakada, K. (1997) “Kansei engineering research on the design of construction machinery.” International Journal of Industrial Ergonomics, 19: 129–146. Picard, R.W. (1997) Affective Computing, Cambridge, MA: MIT Press.

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Proper, K.I., Bongers, P.M. and Grinten, M.P. van der (1999) Longitudinaal onderzoek naar rug-, nek- en schouderklachten. Deelrapport 5: Lokaal ervaren ongemak. De relatie met en de voorspelling van klachten aan het bewegingsapparaat, Hoofddorp: TNO Arbeid. Richards, L.G. (1980) “On the psychology of passenger comfort.” In D.J. Oborne and J.A. Levis, eds., Human Factors in Transport Research, vol. 2. London: Academic Press, 15–23. Schifferstein, H.N.J., Cleiren, M.P.H.D. (2004) “Capturing product experiences: a split-modality approach.” American Journal of Psychology (submitted). Slater, K. (1985) Human Comfort, Springfield, IL: Charles C. Thomas. Sonneveld, M.H. (2002) “Tactiele beleving van de gebouwde omgeving.” In R.N. Pikaar, ed., Ergonomie van de gebouwde omgeving, congresboek 2002, Enschede: ErgoS, 157–164. Theimer, E.T., ed., (1982) Fragrance Chemistry: The Science of the Sense of Smell, New York: Academic Press. Tola S., Riihimaaki, H., Viderman, T., Viikari-Juntura, E.H. and Tanninen, K. (1988) “Neck and shoulder symptoms among men in machine operating, dynamic physical work and sedentary work.” Scandinavian Journal of Work, Environment and Health, 14: 299. Vergara, M. and Page, A. (2000) “System to measure the use of the back rest in sitting-posture office tasks.” Applied Ergonomics, 31: 247–254. Vink, P. and Hark, T.A. ter (2003) “Future demands on comfort in construction vehicles’ interiors according to manufacturers.” In F. Krause, R.E. Bronkhorst and M.P. de Looze, eds., Comfortable Earth-Moving Machinery: Knowledge and Experiences from the Eurocabin Project, Hoofddorp: TNO Work and Employment, 99–105. Vink, P., Hark, T.A. ter and Krause, F. (2001) Future Demands on Comfort in Construction Vehicles’ Interiors According to Manufacturers, Hoofddorp: TNO Work and Employment. Wilder, D., Magnusson, M.L. and Pope, M. (1994) “The effect of posture and seat suspension design on discomfort and back muscle fatigue during simulated truck driving.” Applied Ergonomics, 25: 66–76. Winkel, J. and Westgaard, R. (1992) “Occupational and individual risk factors for shoulderneck complaints: Part II—The scientific basis (literature review) for the guide.” International Journal of Industrial Ergonomics, 10: 85–104. Zhang, L., Helander, M.G. and Drury, C.G. (1996) “Identifying factors of comfort and discomfort in sitting.” Human Factors, 38(3): 377–389. Zimmerman, C.L., Cook, T.M. and Rosecrance, J.C. (1997) “Work-related musculoskeletal symptoms and injuries among operating engineers: A review and guidelines for improvement.” Applied Occupational and Environmental Hygiene, 12(7): 480–484.

Theory on Pressure 3 ADistribution and Seat Discomfort K. Noro, G. Fujimaki, and S. Kishi CONTENTS 3.1 Pressure and Discomfort................................................................................33 3.2 General Discussion ........................................................................................33 3.3 Explanation in a Specific Case ......................................................................34 3.4 Conclusions ....................................................................................................39 References................................................................................................................39

3.1

PRESSURE AND DISCOMFORT

As described in Chapter 2, pressure distribution has a clear relationship with discomfort during sitting. It is among all objective measurement techniques, it is perhaps the most convincing (Looze et al. 2003). Several studies are concerned with this relationship (Ebe and Griffin 2000; Ebe and Griffin 2001; Kamijo et al. 1982; Park and Kim 1982; Vergara and Page 2000). This chapter describes a theory of how this relationship can be explained. The relationship is developed based on years of research at Waseda University and ErgoSeating Co., Ltd. In particular, the change in pelvis angle and body pressure distribution and their relationship will be described in this chapter, and an explanation for the importance of pressure distribution will be given.

3.2 GENERAL DISCUSSION Fujimaki (2002) has shown that there is a relationship between discomfort in time and pressure distribution. A higher pressure resulted in more discomfort, which is in alignment with other studies (e.g., Looze et al. 2003). This chapter concerns the change in time of two objectively measurable factors that are closely connected with the sense of discomfort. These two factors are pelvis angle and body pressure distribution. Both are graphically demonstrated Fig. 3.1 — the seated human model.

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FIGURE 3.1 The seated human model. A B C D E F G H I J K L M N O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

200 180 160 140 120 100 80 60 40 20 0 mmHg

FIGURE 3.2 An example of body pressure measured between the buttock and the seat. Pressure is measured in mmHg.

On earth, human bodies are under the influence of gravitational forces. This means that the body is pulled downward due to its weight. Pressures on the bottom and under the feet carry most of this weight. To change these pressures it is possible to move the pelvis in three directions: yaw, roll, and pitch (Fig. 3.1). The theory in this case is that this movement is experienced when the discomfort rises above a certain threshold. The pressure distribution under the buttock can be measured. Figure 3.2 is an example of a pressure map measured between buttock and seat pan.

3.3

EXPLANATION IN A SPECIFIC CASE

In Fig. 3.3 a model is shown that describes the relationship between pelvis position and pressure (a specific case is shown in Fig. 3.10). The position of the pelvis influences pressure distribution under the buttock and a pressure also influences the position of the pelvis. In this study the relationship is described during a period

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35

FIGURE 3.3 A model showing the relationship between pelvis angle and pressure distribution.

of sitting. With this model, information as to posture changes in the pelvis rotation caused by the pressure changes between buttock and seat pan can be understood over time. The assumption is that the sense of discomfort is affected by this pressure and influences the pelvis position. To describe the relationship, pressure on the seat pan and the pelvis angle were measured during 50 minutes of computer work. Figure 3.4 shows a chair used in this measurement, and the environment of the experiment is shown in Fig. 3.5. The computer displayed at the lower left of this picture shows the body pressure of the subject. Figure 3.6 and Fig. 3.7 present the changes in roll and pitch, respectively, observed in the pelvis movement over time.

FIGURE 3.4 A chair used in this study.

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FIGURE 3.5 Environment of the experiment.

Figure 3.8 presents the fluctuation in average pressure on the seat pan observed during 50 minutes of work, and changes in the maximum pressure on seat pan for the same period are shown in Fig. 3.9. If we compare Fig. 3.6 with Fig. 3.9, causal relationships can be described: The pelvis position changes abruptly the moment body pressure on the buttock exceeds a certain value. Figure 3.10 shows the synchronized movement of pelvis angle and pressure map when the subject is resetting. In previous experiments these phenomena were frequently seen after working more than 30 minutes in one posture. Point A is just before the subject started movement, point B is when the subject was resetting, and point C is just after the subject finished

Roll angle (deg.)

50 40 30 20 10 0 0

10

20

30

40

50

Time (min.)

FIGURE 3.6 Changes in the roll angle of the pelvis during 50 minutes of seated work.

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37

Pitch angle (deg.)

20 10 0 –10 –20 –30 0

10

20

30

40

50

Time (min.)

Average pressure (mmHg)

FIGURE 3.7 Changes in the pitch angle of the pelvis during 50 minutes of seated work.

18 16 14 12 10 8 6 4 2 0

0

10

20 30 Time (min.)

40

50

Maximum pressure (mmHg)

FIGURE 3.8 Changes in the average pressure on the seat pan during 50 minutes of seated work.

200 180 160 140 120 100 80 60 40 20 0 0

10

20

30

40

50

Time (min.)

FIGURE 3.9 Changes in the maximum pressure on the seat pan during 50 minutes of seated work.

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A

B

C

30 B Roll angle (deg.)

20 10

C A

0 –10 –20 36:00

36:10

36:20

36:30

36:40

Time (min. & sec.)

FIGURE 3.10 The relationship between pelvic roll angle and body pressure distribution.

Maximum pressure (mmHg)

the move. There was high pressure on the buttock at point A, and the uncomfortable feeling of the high pressure caused the subject’s macro movement. This macro movement reduced the high pressure on buttock, and the subject was able to maintain the sitting posture for a while longer. From the result, it can be said that the pressure maps at points A and B represent the uncomfortable condition, and the pressure map at point C is the comfortable condition. 200 150 100 50 0 0

10

20

30

40

50

Time (min.) Comfort zone

Discomfort zone

FIGURE 3.11 Discomfort accepted (full line) and discomfort not accepted (dotted line) in the pressure on the buttock.

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The aforementioned analysis provides a reasonable basis for categorizing the body pressure into two zones: discomfort accepted by the human body and discomfort not accepted (Fig. 3.11).

3.4 CONCLUSIONS This chapter has described a theory of the relationship between pressure under the buttock and pelvis position, and a relationship was found between pressure and pelvis position. Also, an explanation and a conclusion as to what could be accepted as discomfort by the human body were given.

REFERENCES Ebe, K. and Griffin, M.J. (2000) “Qualitative models of seat discomfort including static and dynamic factors.” Ergonomics, 43(6): 771–790. Ebe, K. and Griffin, M.J. (2001) “Factors affecting static seat cushion comfort.” Ergonomics, 44(10): 901–921. Fujimaki, G. and Mitsuya, R. (2002) “Study of the seated posture for VDT work.” Displays, 23: 17–24. Kamijo, K., Tsujimura, H., Obara, H. and Katsumata, M. (1982) “Evaluation of seating comfort.” SAE Technical Paper Series 820761. Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discomfort and the relationships with objective measures.” Ergonomics, 46: 985–997. Park, S.J. and Kim, C.B. (1997) “The evaluation of seating comfort by the objective measures.” SAE Technical Paper Series 970595. Vergara, M. and Page, A. (2002) “Relation between comfort and back posture and mobility in sitting-posture.” Applied Ergonomics, 33: 1–8.

Ergonomics 4 Participatory and Comfort P. Vink, S. Nichols, and R.C. Davies CONTENTS 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8

Why Participatory Ergonomics? ....................................................................41 Participants in Design ....................................................................................42 Definition of Participatory Ergonomics.........................................................43 Approaches.....................................................................................................43 The Opinion of Experts .................................................................................44 Essence of the Approach................................................................................44 Participating Groups ......................................................................................45 Stages Towards Implementation ....................................................................46 4.8.1 Stage 1: The Initiative........................................................................46 4.8.2 Stage 2: Problem Identification and Setting Goals ...........................46 4.8.3 Stage 3: Solution Choices..................................................................47 4.8.4 Stage 4: Implementation ....................................................................47 4.8.5 Stage 5: Evaluation ............................................................................47 4.9 Some Problems in Participatory Ergonomics................................................48 4.10 Participatory Ergonomics Methods and Design ............................................48 4.11 Advantage of Using Envisioning Tools.........................................................48 4.12 Virtual Reality and Participation ...................................................................49 4.13 Example of Using an Envisioning Tool ........................................................50 4.14 The Participatory Design Process..................................................................51 References................................................................................................................53

Part of this chapter is based on Vink, P., Lourijsen, E., Wortel, E. and Dul, J. (1992) “Experiences in participatory ergonomics: Results of a round table session during the 11th IEA congress.” Ergonomics, 35(2): 123–127. See also: http://www.tandf. co.uk/journals/tf/00140139.html

4.1

WHY PARTICIPATORY ERGONOMICS?

As stated before, comfort is seen in this book as a subjective phenomenon. The comfort or discomfort of a product can therefore be evaluated only by the user. A product in itself can never be comfortable. That is why much attention is paid to 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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how a user should be involved in the design process. End users should be involved because they have unique insights into their tasks, work, or activities. This involvement of stakeholders such as end users is addressed in participatory ergonomics, and a separate chapter is devoted to this topic. With the help of participatory ergonomics, the design process can be designed with special attention on how to take the participants into account, especially end users. The positive effects of participation have been demonstrated before and are also a reason to pay attention to this topic. The European Foundation for the Improvement of Living and Working Conditions (1999) reports that direct participation in production organizations most often leads to quality improvements (90% of the cases), to reduction of throughput times (60% of the cases), and to reduction of costs (60% of the cases). Several cases in this book, discussed in subsequent chapters, prove that this is also true for the involvement of participants in product design.

4.2

PARTICIPANTS IN DESIGN

In work situations the end user is the worker. This is an advantage compared to studies of consumer products because the target group is more homogeneous and clearly defined. A design is made specifically for a bricklayer, a pilot, or a glazier. In participatory ergonomics this employee is often heavily involved in the design process (Vink et al. 1992), but there are other stakeholders and experts involved as well. More and more design processes have design teams. According to Palacios of Steelcase, a large office furniture manufacturer in the United States, such a team is needed at a very early stage (Palacios and Imada 1998). Figure 4.1 shows why several participants should be involved at an early stage of the design process. Facility management is the part of the team that supplies information on the demands of buyers. Ergonomists, human movement

demands of the buyers

data on ergonomics and posture

health & safety, industry standards

design specifications

data on competitors

workplace items

FIGURE 4.1 In an early stage of the design process data are needed, which compels a design team. In this figure the several kinds of data are described according to Palacios and Imada (1998). Workplace items are organization, used methods, and techniques in the work, aesthetics, culture, etc.

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specialists, or other health and safety executives can provide ergonomics and posture data. Guidelines on production possibilities can be delivered by production management and engineers. Health and safety experts or labor inspectors could be included to supply guidelines on working conditions. Marketing specialists have information, or have access to information, on competitors. Management and employees could supply information on the work that is done and the workplace. Consequently, for a product like an office chair a rather large team is needed.

4.3

DEFINITION OF PARTICIPATORY ERGONOMICS

Participatory ergonomics is the discipline that studies how different parties should be involved in a design process. Participatory ergonomics is the adaptation of the environment to the human (i.e., ergonomics) with the involvement of the proper persons in question (participants) (Vink 2002). Defined in this way, participatory ergonomics is more an umbrella term under which various approaches are found. That is also described in the literature. Kuorinka (1997) describes participatory ergonomics as “practical ergonomics with necessary actors in problem solving.” Wilson (1995) puts it into a wider perspective: “It is the involvement of people in planning and controlling a significant amount of their own work activities, with sufficient knowledge and power to influence both processes and outcomes in order to achieve desirable goals.” Thus, Wilson stresses the fact that the employee should have control over his task, emphasizing that participatory ergonomics is an umbrella concept. The common characteristic is that during the design process attention is paid explicitly to the role of designers, employees, end users, and others involved. In this book, the available knowledge regarding participatory ergonomics is applied to design.

4.4 APPROACHES Among others two approaches are often seen in the design practice: (1) a participatory design process led by a manufacturer of products; and (2) a participatory process led by the end users, usually those at the managerial level. Illustrations of both approaches are found in the next chapters. Chapter 7, on installation workers, is a typical example of an approach led by management of end users. The paint scraper chapter (Chapter 15) is a typical example of a design process led by a manufacturer. There is an important difference between these approaches in terms of setting goals. When the process is guided by the manufacturer, the manufacturer defines the goal of the design process. Often this is a product that anticipates a forthcoming customer need for comfort. In the second approach, it is important that the management and employees of the company define the goal.

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4.5

THE OPINION OF EXPERTS

Participatory ergonomics is a combination of different approaches. However, common themes can be distinguished that are interesting both for designers of comfortable products and for management. In order to review experiences of participatory ergonomics and to identify common themes, a roundtable was organized in one of the international ergonomics meetings (Vink et al. 1992). Eighteen ergonomists (Table 4.1) with experience in participatory ergonomics attended the session. They applied the approach mostly in large companies (10 out of 18) and less frequently in smaller companies (6 out of 18) or sectors of trade (7 out of 18). The roundtable discussion addressed the following questions: • • • •

What is essential in the approach? Who should participate? What are the elements of an ideal process? What problems are seen most often?

The results of the session with the 18 experts are summarized in the next sections.

4.6

ESSENCE OF THE APPROACH

Participatory ergonomics focuses on an ergonomic strategy that can be applied in different ways in different fields of ergonomics. An essential part of this strategy is that direct participation of the stakeholders involved should be strived for in an improvement process. In this process (Fig. 4.2), different stages can be discerned (Vink and Kompier 1997; Noro and Imada 1991). Once the process is initiated, problems should be identified and solutions selected and developed. Then the solutions should be implemented and the effects, as well as the process itself, should be evaluated, with the results feeding back into the process. The 18 experts mentioned several approaches to involve workers. The two most frequently mentioned are one in which the workers are trained to select improvements themselves, and one in which the workers generate ideas and the ergonomist advises on final selection. TABLE 4.1 List of Participants in the Session on Participatory Ergonomics R. Akselsson (Sweden) Etienne (France) M. Hedman (Sweden) C. Hurts (Netherlands) G. Jungetag (Sweden) E.A.P. Koningsveld (Netherlands) I. Kuorinka (Finland) H. van der Molen (Netherlands) L. Patry (Canada)

M.J. Costa (Canada) P. Hasle (Denmark) M. Helander (U.S.) M. Joyce (U.S.) A. Kamp (Denmark) J. Kloosterboer (Netherlands) M. Launis (Finland) A. Oginski (Poland) B. Silverstein (U.S.)

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1. initiative

2. problem identification

3. selection of solutions

4. implementation

5. evaluation

FIGURE 4.2 Different stages of a participatory ergonomics program.

According to the 18 experts, essential elements in the participatory ergonomics approach are • • •

Explicit attention on adapting the environment to human capabilities Striving for direct involvement of the participants Using a stepwise approach

4.7

PARTICIPATING GROUPS

People from many different levels of the company can be involved in the participatory ergonomics strategy (Table 4.2). Involvement depends strongly on the particular way in which groups have to play a role. If the program of improvement is not too radical, only workers and the lower level of management need participate. But in many cases, for example where decisions on budgets or organizational

TABLE 4.2 List of Possible Parties Involved in Participatory Ergonomics Employees/workers Employers/management Maintenance engineers Design engineers Health and safety workers (e.g., occupational physician) Low-level management (e.g., foreman, supervisor) Trade unions Branch organizations Central purchase units In-company health and safety committees

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structures are involved, middle management or even top management should also participate, given their decision-making power. One review (Cotton et al. 1988) argues that involving a group that is only representative of workers in a working group, rather than the workers themselves, will not lead to successful participation. It is also vitally important to have workers develop ideas for improvement in collaboration with managers.

4.8 4.8.1

STAGES TOWARDS IMPLEMENTATION

STAGE 1: THE INITIATIVE

To begin a participatory ergonomics program an initiative should be taken somewhere, either within or outside the organization. Different potential starting points were mentioned by the 18 experts during the roundtable session. For example, workers, occupational physicians, sector organizations, or unions could be aware of a problem and initiate the approach. Of course, successful implementation is more likely when the workers take the initiative or are in need of the improvement and thus desire improvements. In one example mentioned during the session, the occupational health service initiated the process (Patry et al. 1991). Thereafter, a joint committee of workers and management was formed and started discussions at different levels within the company. In this case, the role of the ergonomists was to stimulate discussions to allow the workers to formulate improvements. An initiative can also be created by management (Chapter 10) or from outside the company, for example by the labor inspectorate, a union, or a sector organization (Chapter 6). Starting the project will then be difficult because the attitude of potential participants inside the company may be indifferent or even hostile.

4.8.2

STAGE 2: PROBLEM IDENTIFICATION

AND

SETTING GOALS

The involvement of both workers and management in the problem identification stage was stressed. If the identification of the problem is done without participation of any one group within the company, implementation could become a problem because some people might not be aware that there was a problem! It was also emphasized that in the early stages of the project, goals and a general framework (a common concept) agreed to by all groups should be formulated. This is essential because in a later stage decisions that have unfavorable consequences for one or another of the parties might be necessary. It is quite common that workers and management have different, even conflicting, interests. Having defined a common concept, unity of purpose rather than division is the result. The concept should also be formulated in a language with which the company is comfortable. This could be an improvement in product quality or in the efficiency of the production process. Having such a concept makes it clear to all parties why certain meetings or training programs are necessary. Various tools can be used to identify problems, among them self- or corporate assessment training for workers and management, checklists, work analysis, feedback by video or slides, mock-up

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(Chapters 13 and 20), simulation systems (Chapter 9), Ergomix (Chapter 13), and so on.

4.8.3

STAGE 3: SOLUTION CHOICES

Another essential stage in the participatory process is the selection of solutions and improvements. Again, the 18 experts felt that the workers should always play a role because they are most familiar with their work content. Testing the improvements is very important. Workers should also be informed about other activities needed to make the product so as to establish their contribution to the product. This is needed to achieve better improvements and to avoid worsening the situation for other workers. Two approaches were mentioned for the selection of improvements. In the first, workers are trained to participate in a process of improving the working environment and to set priorities themselves. This recognizes the fact that the workers know their work best. An advantage is that the implementation will be easier; disadvantages could be that the management is neither convinced nor committed, or ineffective improvements are selected. In most situations, workers are not capable of actually designing the product, which makes a next step necessary: the design. Collaboration with product designers is therefore inevitable. The second approach calls for workers to formulate improvements and for experts to make the final selection. The advantage of this approach is that the optimal improvement is chosen. In the discussion it was noted that experience showed that workers and experts commonly selected similar improvement strategies. As mentioned earlier, decisions can lead to conflict and disagreement on appropriate improvement strategies. Therefore, a decision-making structure is needed. To avoid conflict, the improvement strategy should align with the earlier-stated concept, so that everyone can at least understand why the actual improvement is chosen. Consensus on criteria for choosing improvements, such as financial limitations, employment security, and production rates, is also important and should be stated at the beginning of the process.

4.8.4

STAGE 4: IMPLEMENTATION

Using a participatory strategy, implementation can be easy because workers and management have selected the improvements themselves. Of course, attention is needed to facilitate technical realization, promotion, training, and instruction. To achieve implementation of improvements such as optimal workplaces, a permanent, embedded participatory process could be necessary. For example, workers in the company can be trained to work towards ergonomic improvements continuously (train the trainee stage).

4.8.5

STAGE 5: EVALUATION

In this stage the process can be evaluated to improve the implementation or to learn for future cases. It could also be an opportunity to evaluate the effect of the process, to look for new possibilities of improvement, and to learn. Too often this step is

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underestimated (Chapter 7). It can yield valuable information that can be used in marketing (Chapter 15) or to increase knowledge.

4.9

SOME PROBLEMS IN PARTICIPATORY ERGONOMICS

During the session, various problems in applying participatory strategies were discussed. The three most frequently mentioned problems are listed below. •

•

•

Management is not yet convinced of the need for ergonomic improvement. When management does not take the improvement initiative, they will need to be convinced as to the need for improvements, which may be difficult. A solution to this problem is to address the managers in their own language, as described by Kogi (1985). This can mean stressing an economic goal or benefit and giving concrete examples. Workers deny the need for improvement. In this case the starting point should not be the improvement itself; the workers should first be aware of the problems. Starting with training the workers on work problems is essential; thereafter the workers should generate improvements themselves. Conflict between workers and management. As suggested above a common concept should be agreed and set by all groups involved from the start. During the project realization, the unifying goal should be stressed, rather than the divisory one. This makes a compromise understandable and acceptable.

4.10

PARTICIPATORY ERGONOMICS METHODS AND DESIGN

The previously mentioned approach is rather general and not specifically focused on design. In designing an interior, seat, hand tool, or assembly line, specific tools are often used to involve end users actively in the design process. Tools that have previously been used in participatory workplace design projects, in a variety of contexts, include round-robin questionnaires, focus groups, drama, democratic meetings, virtual reality, layout modeling, and mock-ups and full-scale laboratory modeling (Davies 2000).

4.11 ADVANTAGE OF USING ENVISIONING TOOLS Participatory design is a learning process for all participants (Ehn 1988; Ehn et al. 1996). New understandings are created and refashioned, aided by the designer’s tacit, nonverbalized design knowledge and augmented by the participant’s engagement with the environment. Activating design tools can serve to animate and enliven users (Ehn et al. 1996). The tool becomes part of the design activity, helps in verbalizing the participants’ expectations, and stimulates their creativity (Stoeckli et al. 1993).

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Tools can allow both the contemplation of the design problem in an abstract way and the ability to relate solutions to reality (Hornyánszky 1998). A vital prerequisite to allowing participants to be involved in a meaningful way is that they experience being in control of the tools (Ehn 1988; Schön 1983). The insight that the tool gives depends mostly on how easily it can be understood. Successes have been achieved in projects where full-scale objects, mock-ups, and prototypes have been used (see also Chapter 13 and 20). These achievements can be explained by the similarity of the tools to the devices that participants use in their daily lives. The deployment of this type of design method means that the situation and environments that are forged are not merely attempts to verbally describe and imagine the future use of an environment, but instead serve as a method of experiencing that world through direct physical involvement.

4.12

VIRTUAL REALITY AND PARTICIPATION

In addition to the achievements of physical prototyping, another strand of research comes from recent work on the use of virtual reality (VR) (Fig. 4.3). According to a previous overview of virtual reality and systems design (Davies 2001), VR is well suited for the design of large and complex systems that constitute a vehicle. In such designs, many people with diverse areas of expertise are involved over a long period of time (Östman 1998). Among the companies using VR for vehicle design are Volvo, John Deere, Ford, Chrysler, General Motors, British Aerospace, Aerospatiale, and Boeing, to name a few. It saves time and can increase quality because tests with real subjects are replaced by model work. Design in this area includes concept formulation (perhaps looking at the outer form of a car: Is it pleasing to the eye? What is the wind drag coefficient?); planning the actual construction sequence of the final product; and testing issues, such as order of assembly and part fit. People may also be included in the VR design, perhaps as drivers or machinery controllers to ensure that there is enough standing room or that controls can be reached and activated. In some cases, reaching a control —

FIGURE 4.3 A scene from a virtual reality movie to support discussion on the design of the work station.

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FIGURE 4.4 A VR system used in combination with a model to discuss town planning with end users — in this case, citizens. (Photo courtesy of REFLEX, Lund University.)

perhaps a lever — can result in a body position that does not allow enough torque to be applied to actually perform the required action. In other situations, the factor of interest is more obscure, such as sitting comfort over a long period of time or access to driver controls for people of varying body dimensions. Another problem is putting many parts together into small areas, such as in the engine bay, where they compete for space with other elements. The arrangement of wires and pipes has to be drawn in a way that is physically possible, that keeps the amount of material used to a minimum, that allows mounting in the first place and fixing at later stages, and (in many cases) that is not in the way, or is completely hidden. Sometimes the use of a vehicle within a certain environment is of interest, in which case the vehicle is modeled as well as a suitable place for it to be driven in. This allows ergonomic testing in an ecologically valid situation. Combining virtual environments with physical artifacts can further heighten the sense of realism, particularly if the physical controls are coupled to the computer system. In Fig. 4.4 a plan for a town is discussed with end users (citizens) with the support of VR and mock-ups. VR is a worthwhile system to be used before testing comfort with real end users as well.

4.13 EXAMPLE OF USING AN ENVISIONING TOOL One of the envisioning instruments is the Ergomix (Fig. 4.5). It uses blue screen technology, a system that is widely used in the film and television industry to superimpose video images of a person on any background image. Blue screen has also been used in design environments, for example in the design of work stations by research institutes and automotive companies. The use of blue screen technology

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FIGURE 4.5 The Ergomix applied to the design of a bus cabin.

allows links between design drawings (on paper or on the computer) and real workers. Video images of a worker going about his or her normal tasks are superimposed on a drawing of the proposed setup. In other words, the Ergomix links CAD design drawings with real users. Drawings come to life at an early stage of the design process, with people testing the effects of various dimensions. Using this technology, the supply systems for the assembly of car roofs were designed for Inalfa Roof Systems (Tuinzaad et al. 2000). Inalfa is one of the world leaders in roof systems for cars and trucks, and they aim at a healthy, productive, and high-quality assembly line. Next to the logical order of parts and tools, the position and dimensions of the racks for supplying roof parts to the assembly line play a role in the efficiency of the assembly process. Various forms and heights of virtual racks (only drawings of the racks were available) were tested by assembly workers in the Ergomix (Fig. 4.6). The optimal design could be fine-tuned before the mock-up stage. The various designs of the racks and their respective consequences in terms of worker postures and ease of handling were shown on a video. As a result, the workers were motivated to work with the improved racks. Some of the workers were involved in the choice, and most of them were convinced of the increase in productivity (faster handling) and reduction in physical load (less time in awkward postures).

4.14

THE PARTICIPATORY DESIGN PROCESS

Based on the five stages of participatory ergonomics described earlier and on recent literature (Noro 1999; Haines et al. 2002; Vink et al. 2002), a new design process can be described that could be of use in participatory design. The aim of a participatory design process is to allow users to have a large amount of input into product design. Users have tacit knowledge as a result of their high level of familiarity with a

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FIGURE 4.6 The height at which the glass panel is supplied is simulated in the Ergomix. (Pictures taken from video recordings made during the Ergomix session with workers scaled at different heights working with several racks.)

TABLE 4.3 Step 1. Preparation Participants are informed about the project during a central meeting. The aim of the project, strategy (step-by-step approach), members of a steering committee, and possible outcomes are discussed. Step 2. Analysis of tasks, work, and health The tasks, handlings, and work are studied with the use of interviews, questionnaires, observations, or simulation studies. Step 3. Selection of improvements and design Based on the analysis, user requirements are made focused on the goals set in Step 1. These user requirements indicate the design attention points that should be taken into account. A solution session, can be used to generate ideas. Essential in the method is that based on the user requirements where the problems are visualized (e.g., by mixed reality systems), the participants report ideas for improvement. Based on the first ideas, first versions of design could be made, which could be tested in mixed reality systems and adapted. Step 4. Pilot study with the improvements The new design is again tested in a mixed reality environment or in reality, and a prototype could be made. Step 5. Implementation In this stage the new designs are implemented in the actual workplaces. Instruction videos can be added showing new working methods or new ways of operating, and training could be added. In a central meeting all participants are also informed about the new situation. Step 6. Evaluation This step provides information about the effectiveness of the new design. After some time working the effects can be studied with the same techniques used in the step analysis to ensure that any benefit gained is long term. If necessary an adaptation could be added.

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workplace or piece of equipment, which means that they will be more aware of any problems experienced and more able to give advice regarding design modifications. Essential in the participatory design approach is that all participants (end users, designers, and other stakeholders) progress step-by-step toward the end result (a more efficient, healthful, and comfortable design). After (or during) every step in the process, all participants are kept informed. Tools such as those described above could improve the efficiency of this process and ensure consistency in the information presented to participants to keep them informed. This approach contains the steps described in Table 4.3.

REFERENCES Cotton, J.L., Vollrath, D.A., Froggatt, K.L., Lengnick-Hall, M.L. and Jennings, K.R. (1988) “Employee participation: Diverse forms and different outcomes.” Academy of Management Review, 13(1): 8–22. Davies, R. (2000) Using Virtual Reality for Participatory Design and Brain Injury Rehabilitation, Lund: Lund University (Ph.D. thesis). Davies, R.C. (2001) “Applications of systems design using virtual environments.” In Kay Stanney, ed., The Handbook of Virtual Environments, Mahwah, NJ: Lawrence Erlbaum Associates, 1029–1100. Ehn, P. (1988) Work-Oriented Design of Computer Artefacts. Stockholm: Arbetslivscentrum. Ehn, P., Brattgård, B., Dalholm, E., Davies, R.C., Hägerfors, A., Mitchell, B. and Nilsson, N. (1996) “The Envisionment Workshop — from visions to practice.” Proceedings of the Participatory Design Conference, Cambridge, MA: 141–152. European Foundation for the Improvement of Living and Working Conditions (1999) Communique July/August, 1999, Dublin: EFILWC, 2. Haines, H., Wilson, J.R., Vink, P. and Koningsveld, E.A.P. (2002) “Validating a framework for participatory ergonomics.” Ergonomics, 45(4): 309–327. Hornyánszky Dalholm, E. (1998) Att forma sitt rum. Fullskalemodellering i participatoriska designprocesser, Lund: Akademisk avhandling vid institutionen för byggnadsfunktionslära. Kogi, K. (1985) Improving Working Conditions in Small Enterprises in Developing Asia, Geneva: ILO. Kuorinka, I. (1997) “Tools and means of implementing participatory ergonomics.” International Journal of Industrial Ergonomics, 15: 365–370. Noro, K. (1999) “Participatory ergonomics.” In W. Karwowski, ed., The Occupational Ergonomics Handbook, New York: CRC Press, 1421–1429. Noro, K. and Imada, A. (1992) Participatory Ergonomics, London: Taylor & Francis. Östman, J. (1998) Virtual Reality and Virtual Prototyping — Applications in the American Car Industry. Swedish Office of Science and Technology: Overseas Report USA 9806 (in Swedish). Palacios, N. and Imada, A.S. (1998) “A macroergonomic approach to product design.” In P. Vink, E.A.P. Koningsveld and S. Dhondt, eds., Human Factors in Organizational Design and Management IV, Amsterdam: Elsevier, 439–444. Patry, L., Cote, M. and Kuorinka, I. (1991) “Participatory ergonomics of two work stations: Warehouse employees and police officers.” In Y. Quéinnec and F. Daniellou, eds., Designing for Everyone: Proceedings of the 11th Congress of the International Ergonomics Association, Vol. II, London: Taylor & Francis, 1747–1749.

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Schön, D. (1983) The Reflective Practitioner — How Professionals Think in Action, New York: Basic Books. Stoeckli, H.P. and Weber, B. (1993) Zum Unterricht im LEA 1985–1993. DA-Informations 149, Lausanne: Ecole Polytechnique Fédérale de Lausanne. Tuinzaad, G.H., Rhijn, J.W. van, Deursen, J. van and Koningsveld, E.A.P. (2000) Efficient Flow and Human Centered Assembly: The Success of an Interactive Approach, Eindhoven/Hoofddorp: TNO Industrial Technology/TNO Work and Employment. Vink, P. (2002) Comfort, Delft: Delft University of Technology (inaugural address). Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics, 40(4): 435–449. Vink, P., Lourijsen, E., Wortel, E., and Dul, J. (1992) “Experiences in participatory ergonomics: Results of a round table session during the 11th International Ergonomics Association congress.” Ergonomics, 35(2): 123–127. Vink, P., Miedema, M., Koningsveld, E. and Molen, H. van der (2002) “Physical effects of new devices for bricklayers.” International Journal of Occupational Safety and Ergonomics, 8(1): 71–82. Wilson, J.R. (1995) “Solution ownership in participative work redesign: The case of a crane control room.” International Journal of Industrial Ergonomics, 15: 329–344.

and 5 Discomfort Productivity in Improved Bricklaying P. Vink, A.M. de Jong, and E.A.P. Koningsveld CONTENTS 5.1 5.2

Introduction ....................................................................................................56 The Bricklayer................................................................................................56 5.2.1 A First Redesign ................................................................................56 5.2.2 The New Devices ...............................................................................58 5.3 Methods..........................................................................................................59 5.3.1 Experienced Loading .........................................................................60 5.3.2 L5/S1 Maximum Loading..................................................................61 5.3.3 Observing ...........................................................................................61 5.4 Results ............................................................................................................62 5.4.1 Experienced Physical Loading Results..............................................62 5.4.2 L5/S1 Maximum Loading Results.....................................................63 5.4.3 Observing ...........................................................................................63 5.5 Discussion ......................................................................................................65 5.6 Conclusions ....................................................................................................66 5.7 The Bricklayer Assistant................................................................................66 5.7.1 Innovations .........................................................................................67 5.8 Research Question..........................................................................................67 5.9 Methods..........................................................................................................68 5.10 Results ............................................................................................................68 5.11 Discussion ......................................................................................................69 5.12 Conclusions ....................................................................................................70 5.13 Evaluation by Employers...............................................................................70 5.14 General Conclusion........................................................................................71 Acknowledgment .....................................................................................................71 References................................................................................................................71

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5.1 INTRODUCTION Approximately 20,000 bricklayers and 7000 bricklayer assistants are involved in bricklaying in the Netherlands (Jong et al. 2003). They make new houses, offices, and industrial structures and renovate older buildings. Discomfort during this work is very high (Arbouw 1994): 38% of the bricklayers and 36% of the bricklayer assistants in the Netherlands reported back complaints during work (Arbouw 2000 in Jong et al. 2003). Each bricklayer handles manually about 800 to 1000 bricks per day. A bricklayer assistant transports manually about 2400 to 3000 bricks per day (Miedema and Vink 1996). The general agreement is that there is certainly room for improvement, so the total process of bricklaying was improved. The Dutch brick manufacturers’ alliance (KNB), the Dutch bricklayers’ employers alliance (NMPB), the employers’ alliance in the Dutch construction industry (NVOB), and the secondlargest applied scientific research institute in Europe (TNO) developed a new method of laying and transporting bricks. In this chapter a distinction is made between the improvements for bricklayers and those for bricklayer assistants.

5.2 THE BRICKLAYER The bricklayer’s main task is to lay bricks using mortar and trowel. The work is done with care according to a prescribed pattern to ensure that all joints have a uniform thickness and the rows are straight. Actual bricklaying consumes 90% of the time. The waal type of brick (weight 17 N) is used most often and is laid by one hand, with the trowel in the other hand. Other tasks such as setting out material, transportation, and communication consume the other 10% of the time. Traditionally, the bricks are set out at ground level behind the bricklayer, and therefore the bricklayer bends and rotates his back about 800 to 1000 times a day. As far as the frequency of lumbar injuries is concerned, bricklayers belong to the top four trades in the construction industry (Arbouw 1994). The financial and social consequences of sick leave and work disability are large. In 1993, the time lost due to sick leave was 13.3%, and the incidence of new cases of disability in 1 year was 4% of the total number of bricklayers (Arbouw 1994). Of this sick leave, 55% is due to musculoskeletal complaints (Arbouw 1994). The major problem experienced by bricklayers is working between 0 and 0.5 m above the floor (Vink et al. 1996).

5.2.1

A FIRST REDESIGN

The idea was that a raised stack of bricks would reduce the back load as well as the discomfort because the degrees of frequent forward bending would be reduced. However, raising the stack of bricks could cause more discomfort in laying the lower rows. Therefore, the musculoskeletal load factor in raising the height of the bricks was tested in a laboratory experiment. The goal was to find the exact ideal height that resulted in postures with the least discomfort. Figure 5.1 shows three heights for the bricks and mortar. Oxygen uptake, discomfort, and back loadings were tested in each of the three situations (Vink and Koningsveld 1990). The effects of increased height of the set-out bricks and mortar on the energetic workload, discomfort, and biomechanical back stress were investigated. Ten healthy

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FIGURE 5.1 The situation of traditional bricklaying on a scaffolding (A) and on the ground (B).

subjects between 25 and 30 years of age, with at least 3 years of bricklaying experience, were observed during the building of a wall measuring 2 × 1.5 m. Oxygen uptake was recorded during the bricklaying. A questionnaire on locally experienced discomfort was used directly after bricklaying under the different working conditions, and posture was estimated from photos to provide input for a static biomechanical model. If the other tasks remained similar, the energetic workload decreased 2 to 8% with a 0.3 m higher level of set-out bricks and mortar. However, this difference was not significant because the oxygen uptake was influenced by the height of the set-out bricks and mortar, as well as by the height at which the bricks had to be placed in the wall (Fig. 5.2). The Turkey contrast test showed that the oxygen intake was significantly lower during bricklaying at the 0.3 and 0.5 m levels for rows 12, 17, and 22, with respect to normal bricklaying (p < 0 to 0.5). So the heightened set-out of bricks and mortar appeared to lower the energy consumption, especially when bricks were placed in higher rows in the wall (Vink and Koningsveld 1990).

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FIGURE 5.2 Working conditions of the bricklayer, with the set-out bricks and mortar in which the load was measured. (A) the old situation; (B) the set-out bricks and mortar were raised to 0.3 m; and (C) were raised to 0.5 m.

The experienced back load was lowest for the upper rows at the 0.5 m level. However, in comparing the three levels for building a complete wall, raising the set-out to 0.3 m created the least experienced discomfort. Working in the higher rows, the 0.5 m set-out showed the best results in terms of experienced discomfort. Biomechanical analysis of a photo of a subject showed the least lumbar back stress when the bricks and mortar were set out at a height of 0.5 m. Because the combination of working in the higher rows and having bricks and mortar at a height of 0.5 m consumed the least energy, created the best-experienced discomfort results, and produced the least lumbar back stress, the upright position should be pursued.

5.2.2

THE NEW DEVICES

Before implementing innovations, it is essential to have support from the participants and to test the innovations. Therefore, different products were developed and tested in cooperation with the sector organizations. Since 1990, several products designed to raise the bricks and mortar have been developed in order to reduce trunk flexion, but user tests showed that several products were not feasible. An aluminium height-adjustable folding table was developed and tested by bricklayers, but it appeared that the control mechanisms in these tables were too fragile. Malfunctions were caused by mortar on the mechanical parts or by damage during transport. Iron tables turned out to be too heavy to transport between workplaces, and especially for transport to other building sites. Foam boxes used to raise the bricks were lightweight, but they appeared to be unstable in the field tests and were even blown from the scaffoldings by strong winds. User friendliness, safety, implementation possibilities, and discomfort were evaluated in the field tests. After several tests and brainstorming sessions two devices were evaluated as feasible, and the effects of these devices on lumbar loading were investigated in this project. One improvement was a split floor in scaffolds. The traditional scaffolds were adjusted to enable raising of the bricks or to lower the floor where the bricklayer stands. By adding extra mounting provisions to the pipes of the scaffolding, boards

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FIGURE 5.3 Bricklaying with a split-floor scaffolding. The floor of the brick layers (two persons on the left in the picture) is lowered causing the bricks and mortor raised 0.5 m.

could be positioned at various heights by the scaffolders. This increases the possibilities for lowering the level of the boards for the bricklayer 0.5 m, or for raising the level of the boards where the bricks and mortar are positioned (Fig. 5.3). The so-called HC scaffolding, which can be set up by a crane, facilitates this lowered bricklaying and reduces the workload of the scaffolder. From the research mentioned above, it turned out that, ideally, the position of the bricklayer is lowered 0.5 m because he starts higher on the wall and the bricks are set out at 0.5 m. Another improvement involved the use of shores. A few bricklayer companies use very simple shores of wood and iron or aluminium that can be placed on the scaffold (Fig. 5.4). This solution also raises the bricks and mortar 0.5 m. The total weight of these shores was 100 to 200 N, depending on the materials used. For heavier shores, the boards and supports can be split to simplify transport.

5.3 METHODS To study the effects precisely, measurements should be taken in the actual situation. However, measuring effects in a naturalistic setting is difficult, and a laboratory study does not guarantee the same effects in practice, especially in the construction industry. Every building is different, every building site is different, and several factors such as

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FIGURE 5.4 Bricklaying with a shore, with bricks and mortar raised 0.5 m.

body space do influence postures. Valid and reliable measurements are, in fact, impossible. In this study it was also impossible to find enough situations in practice to observe both devices separately in exactly the same situation. From the first observations, the impression was that the working methods applied did not differ much between working traditionally and working with raised bricks. The effects that were evident were assumed to be caused by the raising of set-out bricks and mortar. Therefore, in this study a combination of three indicative experiments was used to find differences between working traditionally and working with the bricks raised 0.5 m: (1) questioning about experienced loading immediately after the work done; (2) estimating the maximum loading of lumbosacral junction L5/S1 from field recordings; and (3) observing the specific bricklaying task.

5.3.1

EXPERIENCED LOADING

To get an indication of the perceived loading, the design for the study had to take various aspects into account. Since short-term effects, such as getting accustomed, should be excluded, a group was needed that had been working with the raised bricks for a longer period. Nevertheless, experience with the traditional way of working was also essential and had to be fresh in mind. Therefore, out of all bricklayers a group was defined that had worked for more than 2 years traditionally and that had been working with the raised bricks for approximately 50% of their time over the

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past year. By interviews in the sector, one bricklaying company was found that met these criteria. All 25 bricklayers from this company were asked to complete a questionnaire on experienced loading with the 2 systems. Questions were asked about their preference for traditional working or for working 0.5 m raised, the influence of each system on their work pace, and the discomfort they experienced in the different body regions after a day of working. Differences were tested with the t-test for paired comparison (p < 0.05).

5.3.2

L5/S1 MAXIMUM LOADING

To estimate the L5/S1 peak loading in the traditional and in the 0.5 m raised way of working, the postures were estimated and the forces on the L5/S1 segment were calculated. As mentioned earlier, most of the working time is consumed by bricklaying itself. To make a comparison possible, an average task with waal bricks was recorded in the traditional situation and with the materials raised 0.5 m. Three bricklayers were found who worked one day in the traditional situation and one day with the bricks raised 0.5 m, performing comparable tasks. The three bricklayers were videotaped during the 2 days. For each subject and each condition, seven images were selected from the videotapes where the torso flexion was highest. The average angles of each body segment were calculated from these selected images, tested with the t-test for paired samples (p < 0.05), and put into the 2-D static strength prediction program model (Chaffin and Andersson 1991) to calculate the L5/S1 load.

5.3.3

OBSERVING

Using existing studies and interviews with specialists in bricklaying, the average work was defined: working with the waal bricks; some windows, some corners; working with teams of three bricklayers and one assistant; and so on. Construction sites were then located where this average bricklaying work could be found. Ten subjects were observed using both the old and the new working methods and were videotaped during 1 day of work. Additional measurements were performed on the weights of the bricks and on handling distances. The time spent on several tasks and the frequency of handling were measured with a stopwatch. From the videotapes, the angles of some body segments compared to the vertical were estimated (trunk, upper arm, lower arm, and head). Also, estimations were made of the horizontal distance between ankle and hand, the vertical distance between ground and hand, and the asymmetry in trunk posture. These data were analyzed and evaluated according to the guidelines on physical workload for the construction industry (Table 5.1). The NIOSH equation was used for lifting; the Mital guidelines for pushing, pulling, and carrying (Mital et al. 1993); and for posture and repetitive work the ISO/CD 11226 (1995), NF X 35–106 (1985), and prEN 1005-4 (1996). The assessments, therefore, are based on available international guidelines and on consensus among Dutch ergonomists and the construction industry (Molen and Delleman 1997).

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TABLE 5.1 Abstract of Guidelines Used to Evaluate the Workload Evaluation Activity

Source

Lifting One-handed lifting Pushing/pulling Carrying

NIOSH* Mital** Mital** Mital**

Criterion

Green

Whole body judgment Various <MPL Max force >P90 male Max force >P90 male Max force >P90 male

Yellow

MPL–3xMPL P25–P90 male P25–P90 male P25–P90 male

Red

>3xMPL
Posture (static as well as repetitive movements, more than 2 per minute) Upper arm ISO/CEN*** >60° <1 hour 1–4 hours >4 Elevation Low back 1 ISO/CEN*** >60° Flexion <1 hour 1–4 hours >4 Low back 2 ISO/CEN*** >0° Rotation <1 hour 1–4 hours >4 Low back 3 ISO/CEN*** Overextension <1 hour 1–4 hours >4 Neck 1 ISO/CEN*** >25° Flexion <1 hour 1–4 hours >4 Neck 2 ISO/CEN*** >0° Rotation <1 hour 1–4 hours >4 Other joints ISO/CEN*** Extreme <1 hour 1–4 hours >4 angles

>2/min >3/min >4/min >5/min

NF NF NF NF

Repetitive handlings (with the hands) X**** Force >85N <1 hour X**** Force >60N <1 hour X**** Force >35N <1 hour X**** Force >20N <1 hour

1–4 1–4 1–4 1–4

hours hours hours hours

>4 >4 >4 >4

hours hours hours hours hours hours hours

hours hours hours hours

Green = Safe. (For lifting, this means that in applying the NIOSH 1991 equation the maximum permissible limit [MPL] should not be exceeded. Pushing is considered safe if more than 90% [P90 = 90 percentile] are able to perform the task.) Yellow = Improvements will be needed over time. Red = Improvements are needed immediately. * NIOSH equation described in Waters et al. (1993). ** Mital et al. (1993). *** ISO/CD 11226 (1995) and prEN 1005-4 (1996). **** NF X 35–106 (1985) and Kilbom (1994).

5.4 RESULTS 5.4.1

EXPERIENCED PHYSICAL LOADING RESULTS

Twelve bricklayers completed the questionnaire, a 48% response. Six respondents had no history of back complaints, but others had suffered from back complaints during at least some time over the past 12 months. All respondents preferred bricks and mortar raised 0.5 m, a significant difference. The handling time did not differ significantly (nine bricklayers reported no difference and three reported that quicker work is possible in the raised situation). The raised situation resulted in less dis-

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63

12

10

8

6

4

2

0 neck

upper back

lower back

shoulder

elbow

wrist/hand

FIGURE 5.5 The body region where 12 bricklayers report discomfort reduction while working with bricks and mortar raised 0.5 m.

comfort. The effects on body segments were largest for the lower back. In the raised situation, the discomfort in the lower back decreased significantly (the mean for old discomfort in the low back was 4.2, and 2.4 for new discomfort, p = 0.03) (Fig. 5.5).

5.4.2

L5/S1 MAXIMUM LOADING RESULTS

The measured angles are shown in Table 5.2. All angles were influenced by the working method (Table 5.2), especially in regard to the trunk. As could be expected, the trunk is significantly more upright when working with the 0.5 m raised bricks (difference 69.8°). This resulted in an estimated decrease of 56% in the mean compression force (2.3 kN traditionally and 1.6 kN with raised bricks).

5.4.3

OBSERVING

The observations made several aspects clear. The time consumption of the different tasks was not significantly different. The most important difference in posture was found in trunk flexion (Table 5.3). In the traditional situation (three to four times per minute for more than 4 hours a day) the bricklayer will bend his back more than 60°. This is evaluated as a high health hazard (red in the system of Table 5.1). In working with 0.5 m raised bricks the back is bent in the same frequency, but the flexion mostly does not exceed 20°. Working with waal bricks of 17 N is acceptable in this situation (green). However, working with bricks heavier than 20 N, with a frequency of five bricks per minute during a period of 2 hours, creates a yellow hazard.

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TABLE 5.2 Average Angles of Three Subjects (Defined in Figure) Shoulder Elbow Trunk Knee Ankle

Angle working traditionally (sd) –88.9 (6.4) –74.9 (5.0) –5.9 (10.3) 116.8 (5.6) 83.3 (3.1)

Angle working 0.5 m raised (sd) –66.6 (7.4) –38.1 (9.8) 63.9 (2.4) 99.9 (3.2) 84.7 (1.3)

sd = Standard deviation of the 21 recorded angles (3 subjects × 7 measurements). All differences significant (p < 0.05).

Although observed in only 2 subjects in this study, the best results were obtained in the situation where the floor on which the bricklayer stands is 0.5 m lower than usual. This is in alignment with the experienced discomfort.

5.5 DISCUSSION All experiments indicate that bricklaying with bricks and mortar raised 0.5 m is favourable. The bricklayers experience the work better, the lumbar peak load estimation on L5/S1 is lower in the raised condition, and observation of the work shows that working with raised bricks reduces the risk. However, the conclusions should be drawn with care because this study had only a limited number of subjects observed under nonstandardized conditions at construction sites. Each part of these experiments had its drawbacks:

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TABLE 5.3 Number of Observed Trunk Flexions during a Day Working with Waal Bricks, Averaged over Ten Observed Bricklayers (Sd) Trunk flexion Working traditionally Working with bricks raised 0.5 m Bricklayer standing 0.5 m lower

>20° 912 (112) 211 (45) 42*

>60° 842 (128) 12 (2) 2*

* Values based on observation of only two subjects.

• • •

• • • •

It was impossible to study the effects of each product (split scaffolding and shores) separately. The questionnaire had a low response. Bricklayers completing the questionnaires could be biased because the new devices were promoted by management with the motive to reduce musculoskeletal load. Only three subjects could be found that had comparable work for biomechanical analyses. Dynamic work was analyzed with a static biomechanical model. Only ten subjects were observed. Observations were evaluated with guidelines that still have weak bases.

This study illustrates that experimental measurements in a naturalistic setting do have constraints. It is clearly not always possible to follow the rules of the experimental paradigm (controlling certain factors and at the same time manipulating others). Furthermore, the validity of the evaluation of the loadings is uncertain. However, all three experiments trend in the same direction, and therefore the results from these studies are used to advise bricklayers positively on implementing the better way of working. Comparison with other studies on bricklayers strengthens the outcome. The fact that bricklaying is heavy work is described by Jørgensen et al. (1991). The finding that bricklayers bend three to four times per minute is comparable to a study among German bricklayers (Luttman et al. 1991). Although there are large differences in the working methods, Luttman et al. (1991) established a handling frequency of 2.9 times per minute. Also in Germany, Jäger et al. (1991) calculated the compression forces and concluded that the compression forces are more acceptable when bricks are grasped from the minimal height of 0.5 m. The previous laboratory study (Vink and Koningsveld 1990) showed a decrease of 21% in biomechanical loading (from 1.9 kN traditionally to 1.5 kN with materials raised 0.5 m at lumbar segment 3 and 4), whereas in this field study a reduction of 30% was found. Other measurements such as oxygen uptake and electromyography readings also support our results. Jørgensen et al. (1991) stated that the large number of repetitive trunk flexions resulted in muscular fatigue that could be found in the electromyography pattern. Oxygen uptake was also significantly lower in a 0.5 m raised situation (Vink and Koningsveld 1990).

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However, regardless of the improvement created by using raised bricks and mortar, there is still room for further improvement. The frequent handling in bricklaying (three to four times per minute) and other tasks such as setting out, carrying, and cleaning offer many possibilities for improvement. Also, the situation in which the bricklayer positions himself 0.5 m lower is preferable, which means that the scaffolding with the split floor should be promoted in combination with training as to how the scaffolding should be used.

5.6 CONCLUSIONS The major discomfort experienced by bricklayers is related to working between 0 and 0.5 m above the floor level. This study indicates that the problem can be partially reduced by raising the stack of bricks with shores or by using scaffolding provisions that allow bricklayers to stand 0.5 m lower than usual. Experiments and literature support this finding, and bricklayers experience the reduction in discomfort. Estimations of lumbar back load show a significant reduction. Observations evaluated with appropriate guidelines show a shift from not acceptable to acceptable. Further improvements to reduce the bending frequency and to improve the other tasks of the bricklayer are advised.

5.7

THE BRICKLAYER ASSISTANT

The bricklayer assistant’s main task is to prepare the work for the bricklayers. Sometimes scaffoldings have to be made, and transport of bricks and mortar to two or three bricklayers is always the case. An assistant transports approximately 2400 to 3000 bricks a day (Fig. 5.6). He spends 46% of his daily working time on transporting bricks, 13% on transporting mortar, 4% on removing scaffolding, and 37% on general activities such as servicing tools, cleaning, deliberation, and so forth (Meijer 1994). Traditionally, assistants perform their tasks manually. This includes the manual loading of the wheelbarrow (repetitive lifting), trundling the wheelbarrow (lifting, carrying, pushing), and unloading (repetitive lifting). For loading and unloading a cramp is sometimes used, with which five to eight bricks can be picked up together. The objective of this study was to establish the differences in physical load for the bricklayer assistant between the traditional and the new way of handling bricks. The traditional working method was analyzed in 1993. The development of new aids took 4 years, and this work was evaluated in 1998.

5.7.1

INNOVATIONS

Several devices have been developed to eliminate the manual loading, unloading, and transport of bricks. A pincer device (Fig. 5.7) is available with which 200 to 400 bricks can be picked up and transported with a crane. Because of this mechanization, the physical load on the assistant has almost been eliminated. Traditionally, the bricks are delivered in bulk or as indivisible packs. In the new way of working the packs of bricks can be picked up by a kind of forklift mounted on a crane and moved from and to the truck. This brick pack can be transported by

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FIGURE 5.6 A task of the bricklayer assistant: transporting bricks.

FIGURE 5.7 Two pincer devices for transporting 200 to 400 bricks with a crane. This is the completely mechanized working method to eliminate manual lifting by the bricklayer assistant. In part A a device is used for scaffolds that can be reached from above. In part B the device allows workers to place the bricks from the side.

crane directly to the place where the bricklayer works. It was a big effort to convince the supplying industry (companies that have the brick ovens and transport companies), the bricklaying companies, and general contractors to make these investments. A participatory approach was needed in which the management and representatives of sector organizations from all of the mentioned industries participated. Prototypes were tested and adapted on several sites.

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5.8

RESEARCH QUESTION

To convince participants to invest, the effect of the improvements on musculoskeletal loading was studied. Most companies were not convinced of the positive effect. Therefore, our hypothesis was that the mechanized and partly mechanized way of working have no effect. Also, if the new way of working should be promoted it would be of great help if the costs were reduced. In this study, therefore, the costs of the old and new methods were estimated.

5.9 METHODS Two conditions were observed: traditional working and mechanized working. Five bricklayer assistants were observed and videotaped during a full day of work under each set of conditions. As mentioned earlier, loading and unloading the wheelbarrow and transport with the wheelbarrow consumed most of the time. Therefore, construction sites were selected where these activities constituted most of the work. Onsite estimations were made in the following areas: •

• •

Forces exerted on the hand by carrying and lifting the wheelbarrow, eightpacks of bricks, and aids. These measurements were recorded by a dynamometer (accuracy 1 N). Frequency of handling and durations of the tasks were recorded by stopwatch. Experts selected the three most demanding tasks (which appeared to be loading, unloading, and transport), and these tasks were sagittally videotaped to record body postures.

Several distances visible on the videotape were measured: the horizontal distance between ankle and hand; the vertical distance between ground and hand; the asymmetry and the posture of the trunk (angle between vertical and trunk); and the upper arm in space. These data were analyzed and evaluated according to the guidelines on physical workload for the construction industry (Table 5.1). The financial consequences of the two methods were roughly estimated based on a situation in which 6000 bricks (a medium-sized building site) should be set out. A calculator employed by a bricklaying company that makes bids as a subcontractor to the general contractors calculated the costs.

5.10 RESULTS Most activities in the traditional way of working are considered red, according to Table 5.1. In loading and unloading the wheelbarrow, two bricks (waal type, 17 N; and maas type, 31 N) were usually lifted in each hand, for a total weight of 68 N or 124 N. Sometimes a cramp was used, in which five to eight bricks could be picked up by one hand (85 to 248 N for the bricks + 5 N for the cramp). A wheelbarrow carrying 80 bricks was usually loaded or unloaded in approximately 5 minutes. The total loading and unloading time was 5 hours out of the 8-hour work day.

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Working with the wheelbarrow also resulted in unacceptable postures during loading and unloading. The estimations of the most flexed position of the trunk varied between 60 and 80° (70° average). Loading and unloading bricks positioned at 0.5 m above the ground resulted in trunk flexions of 0 to 20° per minute. However, this range was unacceptable because of its high frequency (3 to 4 times per minute). Lifting and pushing the wheelbarrow was unacceptable due to the high weight of the bricks and wheelbarrow together — approximately 1300 N (1190 to 1410 N). From the force estimates it appeared that 500 N (varying from 462 to 541 N) is carried by the hands and 800 N by the wheel. The initial required pushing force is 200 N (165 to 230 N) followed by 60 N (48 to 77 N) continuously, which is not considered to be the major problem. The new way of working included positioning the bricks directly onto the scaffoldings from the truck. The number of bricklayer assistants needed is thereby reduced drastically. Activities that still require bricklayer assistants are preparing the scaffoldings, planning which bricklayer needs the bricks, transporting mortar (which is still a heavy task), resetting packs of bricks (a highly variable workload), and crane operating. More effort is now needed for planning than in traditional bricklaying. The bricklaying company’s cost estimate for setting out 6000 bricks traditionally is $440 (16 hours of bricklayer assistant time). Under mechanized conditions, the cost estimate is $248 (2 hours of bricklayer assistant time, $110; renting a crane and crane operator, $138).

5.11 DISCUSSION Regarding the research question, the hypothesis that the innovations have no effect is false. The innovations described earlier should be promoted in the construction industry. Tasks with the highest musculoskeletal demands, such as loading, unloading, and pushing a wheelbarrow, are eliminated in the new way of bringing bricks to the bricklayers. This type of work consumed 46% of the traditional working day. Promotion of these innovations will not be too difficult because the financial advantages are shown to the bricklaying company for medium-sized jobs. The traditional transport of 6000 bricks requires 2 days’ work by the bricklayer assistant, which costs approximately $440. Transporting 6000 bricks completely mechanically (30 charges of 200 bricks each in the pincer device) costs $248 (2 working hours and 1 hour renting a crane and operator). To build one house the system is not cost-effective; the financial advantage exists if brick transport is required only once in 2 days. This is normally the case at a building site of more than four houses. Of course, other costs such as rebuilding the ovens and making special devices for transport are not included. These costs are borne by the brick manufacturing companies, but they did raise the brick price and will have a return on their investment in a few years. The transport of mortar still needs attention. In the old situation it didn’t consume much time (13% of the working time), but as the brick is transported faster and the number of bricklayer assistants decreases, mortar transport might have to be done more frequently.

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The method of evaluation can also be discussed. All evaluation methods have weaknesses, and in fact our knowledge is not far enough advanced to come to a solid conclusion of acceptable or not acceptable. Even for the red–yellow–green guideline applied in this project, the knowledge is in fact scarcely available. A major point on this study is the fact that only observations are used. No exact recorded data are available, and no perceived or experienced loading is measured in this study. Other studies (Arbouw 1994) show that the work of the bricklayer assistant is perceived as heavy, with a high discomfort level that is in alignment with our results. Also, bricklayer assistants have a high frequency of sick leave (17.7%) compared to the Dutch construction industry as a whole (12.1%) (Arbouw 1994). The same situation is found in other countries. In the United States the injury rate is 14.7%, compared to 3.1% in all construction occupations (Hsiau and Fosbroke 1996). All told, a large number of studies support the findings of unacceptable loading for the bricklayer assistant.

5.12 CONCLUSIONS This study indicates that the major problems in the work of bricklayers and bricklayer assistants can be improved. For bricklayers a lowered floor in the scaffolding is a good improvement, reducing the discomfort. For the assistants, loading and unloading the wheelbarrow created an unacceptably high load. The work of the bricklayer assistant is more acceptable if this part of the job is eliminated. The innovations tested eliminated the wheelbarrow work, thereby promoting the innovations. However, the task of manually transporting mortar by the wheelbarrow is still too heavy and also needs innovations.

5.13

EVALUATION BY EMPLOYERS

A few years after introduction of these innovations a study was done regarding their implementation (Jong et al. 2003). This study shows that more than half of the sector uses the new devices. Also, 25 employers were interviewed (Jong et al. 2003), and the results from this study show that important reasons for buying the new system (Table 5.4) are improvement of working conditions, a positive cost–benefit ratio, and increase in productivity. The difficulty in using it on some construction sites and the dependency issue of whether or not to use the crane of the main contractor are reasons for not adopting the system. Other positive aspects seen as important by the employers are the involvement of many parties and many tests in the field. In this project the bricklayer sector organization, unions, main contractors, researchers, and suppliers were all heavily involved (the participatory ergonomics approach). Negative aspects mentioned by Jong (2003) included perceptions of an unstructured process and no direct employee involvement. This shows that the reduction of discomfort is very intensive. Also, the importance of the combination of discomfort reduction and cost–benefit improvements has been shown to be profitable.

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TABLE 5.4 Reasons for Adopting the New Way of Working, According to Employers Improvement in working conditions (37%) Positive cost–benefit ratio (74%) Productivity increase (26%)

5.14

GENERAL CONCLUSION

This large project shows that discomfort reduction can be achieved by firm efforts, which can prevent musculoskeletal problems in the future. More than half of the sector has implemented the improvements, which can be seen as a success. Analysis of the parts of bricklayers’ bodies that experienced much discomfort in the traditional situation was important in order to focus the development of ideas. Collaboration with different parties as well as combination of work-improvement results with financial benefits are important success factors. On the average, employees notice the improvements and employers are satisfied as well. Perhaps a more structured design process and more direct employee involvement could have led to even better results.

ACKNOWLEDGMENT The authors want to thank Arbouw, Mr. Jac de Kroon, the Dutch brick manufacturers’ alliance (KNB), the Dutch bricklayers employers’ alliance (NMPB), and the employers’ alliance in the Dutch construction industry (NVOB) for supporting this study.

REFERENCES Arbouw (1994) Work and Health in the Construction Industry, Amsterdam: Arbouw (in Dutch). Chaffin, D.B. and Andersson, G.B.J., eds. (1991) Occupational Biomechanics, 2nd ed., New York: Wiley & Sons. Hsiao, H. and Fosbroke, D. (1997) “Determining research focus for reducing overexertion injuries in the construction industry.” In Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Tampere, Finland: Vol. 6, 118–120. ISO/CD 11226 (1995) Ergonomics — Evaluation of Working Postures (ISO/TC159/SC3), Osaka: JISC. Jäger, M., Luttman, A. and Laurig, W. (1991) “Lumbar load during one-handed bricklaying.” International Journal of Industrial Ergonomics, 8: 261–277. Jong, A.M. de, Vink, P. and Kroon, J.C.A. de (2003) “Reasons for adopting technological innovations reducing physical workload in bricklaying.” Ergonomics, 46(11): 1091–1108. Jørgensen, K., Jensen, B.R. and Kato, M. (1991) “Fatigue development in the lumbar paravertebral muscles of bricklayers during the working day.” International Journal of Industrial Ergonomics, 8: 237–245.

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Kilbom, Å. (1994) “Repetitive work of the upper extremity, part I: Guidelines for the practitioner.” International Journal of Industrial Ergonomics, 14: 51–57. Luttman, A., Jäger M. and Laurig, W. (1991) “Task analysis and electromyography for bricklaying at different wall heights.” International Journal of Industrial Ergonomics, 8: 247–260. Meijer, J.G. (1994) Analysis of Bricklaying, Ede: SAOB (in Dutch). Miedema, M. and Vink, P. (1996) Risk Assessment and Evaluation in Bricklaying, Amsterdam: Arbouw (in Dutch). Mital, A., Nicholson, A.S. and Ayoub, M.M. (1993) A Guide to Manual Materials Handling, London: Taylor & Francis. Molen, H. van der and Delleman, N.J. (1997) “Arbouw guidelines on physical workload for the construction industry.” In Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Tampere, Finland: Vol. 6, 197–199. NF X 35-106 (1985) Ergonomie — Limites Défforts Recommandées pour le Travail et la Manutention au Poste de Travail, Paris: AFNOR. PrEN 1005-4 (1996) Safety of Machinery — Human Physical Performance, Part 4: Evaluation of Working Postures in Relation to Machinery (CEN/TC122/WG4), Delft: NNI. Vink, P. and Koningsveld, E.A.P. (1990) “Bricklaying: A step by step approach to better work.” Ergonomics, 33(3): 349–352. Vink, P., Munnik, M.J. and Voorde, J.A.W. ten (1996) “Bricklaying company Van Berkum improves bricklaying.” In M.A.J. Kompier, R.W.M. Gründemann, P. Vink and P.G.W. Smulders, eds., Aan de Slag!, Alphen aan den Rijn: Samsom, 105–115 (in Dutch). Waters, T.R., Putz-Anderson, V., Garg, A. and Fine, L.J. (1993) “Revised NIOSH equation for the design and evaluation of manual lifting tasks.” Ergonomics, 36: 749–776.

Discomfort in 6 Reducing Work with New Products for Glaziers A.M. de Jong, H.F. van der Molen, and P. Vink CONTENTS 6.1 6.2 6.3 6.4 6.5 6.6

Discomfort among Glaziers ...........................................................................73 Design of Mechanical Aids ...........................................................................74 Steps in the PE Approach for Glaziers..........................................................74 Diffusion at the Sector Level.........................................................................75 Results at the Sector Level ............................................................................76 Results ............................................................................................................76 6.6.1 Results of Step 2: Analysis................................................................76 6.6.2 Results of Step 3: Selection of Improvements..................................77 6.6.3 Results of Step 4: Pilot Study with Improvements...........................78 6.6.4 Results of Step 5: Implementation ....................................................79 6.6.5 Results of Diffusion at the Sector Level ...........................................79 6.6.6 Results of the Effects Study at the Sector Level ..............................80 6.7 Discussion ......................................................................................................82 6.8 Conclusions ....................................................................................................83 Acknowledgment .....................................................................................................83 References................................................................................................................84

Parts of this chapter are reprinted from Jong, A.M. de and Vink, P. (2000) “The adoption of technological innovations for glaziers; Evaluation of a participatory ergonomics approach.” International Journal of Industrial Ergonomics, 26: 939–946. (Copyright 2000, with permission from Elsevier)

6.1

DISCOMFORT AMONG GLAZIERS

Among glaziers, discomfort is high. Some years ago, studies of this sector level (Arbouw 1996) showed that glaziers had a physically demanding job. Windowpanes weighing from 50 to 200 kg are often lifted manually to the second floor. Transporting the windowpane manually is frequently observed, and the sector 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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organizations recognize the problem of high musculoskeletal load resulting in discomfort and perhaps even back injuries in the long run. Therefore, most companies agree that there is certainly room for improvement in working methods. However, changing working methods can be very difficult, and designing new methods consumes energy and time. Sometimes the workers do not see the necessity, sometimes the improvements are too costly, or sometimes the workers may refuse to use new working methods. Besides the difficulties in implementing them, it is of course important to find the most appropriate improvements aimed at reducing the major problems.

6.2

DESIGN OF MECHANICAL AIDS

To redesign the working methods in the most appropriate way and to increase the chances of successful implementation, a special approach was developed based on the participatory ergonomics (PE) approach described in Chapter 4. In the present study this PE approach was applied to three small glazier companies to find the most optimal improvements. For the purpose, mechanical aids that reduce the major musculoskeletal loadings were designed. These were developed with the understanding that they should be appropriate for use by all glaziers. After the PE approach, a campaign was organized to promote use of these aids in the glazier sector. A few years after promotion, the effects in the sector were evaluated. Those effects are described in this chapter, especially with respect to the adoption of new methods of work. To understand the role of the different steps in the PE process, the final result of the approach is studied, as well as the separate effects of each step followed in the campaign.

6.3

STEPS IN THE PE APPROACH FOR GLAZIERS

As described in Chapter 4, one of the important elements in the PE approach is that all participants (of the companies, sector organizations, and advisors) progress step-by-step toward the end result (reduction of physical workload). In this project, all participants in the three companies were kept informed after every step in the process. Glaziers from these companies completed checklists, developed suggestions for improvements, tested improvements, and gave their preferences. These results were discussed with them. A steering group discussed the headlines, costs, and benefits. Members of this group included one glazier; management representatives of the three companies; representatives of Arbouw (the Dutch institute for improving working conditions in the construction industry), FOSAG (the glaziers’ sector organization), and TNO (the second largest applied scientific research organization in Europe). A steering group decision, for example, was to determine which improvements could be used in the majority of companies within the sector. The following steps were followed in this project. •

Step 1: Preparation All glaziers of the three companies were informed about the project during a central meeting. The aim of the project (reduction of physical workload),

Reducing Discomfort in Work with New Products for Glaziers

•

•

•

•

75

the step-by-step approach, members of the steering committee, and possible outcomes were presented by the consultants from TNO. Step 2: Analysis In previous studies (Arbouw 1996) the work and health problems had already been studied. Pane lifting and pane transport, horizontally as well as vertically, were experienced with a lot of discomfort, and objective data showed comparable results. Experts made additional observations in the three participating glazier companies. In a meeting with glaziers of the three companies, these results (older studies, recent observations) were discussed. The main problems were defined based on these discussions. Step 3: Selection of improvements User requirements were made for the main problems defined in Step 2. These user requirements indicated the solutions that should be developed and selected. Ideas for improvements were generated in solution sessions, following a procedure described in detail elsewhere (Urlings et al. 1994a, 1994b). Essential to the solution session is that a good description of the situation around the problem is presented to — in this case — a group of glaziers, ergonomic experts, product designers, and management of the sector organization and of the participating glazier companies. Inspired by the description of the problem, everyone draws or describes a solution on paper (silent round). The papers are collected and the chairman discusses the ideas without knowing whose they are. After this, additional solutions are asked, inspired by the previous ideas. Then the group estimates the effect of the ideas on discomfort and efficiency, as well as the feasibility of the ideas. In two meetings of the steering group, solutions are further prioritized based on feasibility, user friendliness, costs, and estimated effects on health. Step 4: Pilot study with improvements Various companies making comparable products were asked to design products based on drawings and descriptions from the solution session. These were discussed with experts (ergonomists and product designers from TNO), and prototypes were made of the new mechanical aids. Three glazier companies worked one day using these aids. The work was observed by ergonomists from TNO and partly by members from the sector organization Arbouw. Based on these observations and on interviews with the glaziers and Arbouw, a list of improvements was made. The mechanical aids were adapted and tested again by two glazier companies. Step 5: Implementation In the three glazier companies, the experience with the mechanical aids was discussed. Management and the glaziers together decided which aids were needed and should be purchased by the companies.

6.4

DIFFUSION AT THE SECTOR LEVEL

The previous steps were input to set up a campaign that was organized to promote understanding and use of the improvements.

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Guidelines were made and agreed upon by employers and employees of the sector. These Arbouw guidelines were based on measurements of what was acceptable in terms of physical load and contained elements such as the maximum acceptable weights of windowpanes. A brochure and a videotape were made to explain the several solutions, and all 2050 companies of the Dutch glazier sector were invited to attend a demonstration day. All mechanical aids were demonstrated there, and influential representatives of the glazier industry explained why it is important to innovate. Every visitor received the videotape and the brochure, and the same information was also published in the journals of the sector and Arbouw. Companies that were members of the sector organization FOSAG and were not able to attend the demonstration day received a videotape by mail.

6.5

RESULTS AT THE SECTOR LEVEL

In the long run, this approach to reducing musculoskeletal discomfort and the use of sick leave is rather expensive and time consuming. Therefore, it is interesting to know what the effects of the stepwise approach and the campaign are. The effects among glazier companies were evaluated. A year after the demonstration day a questionnaire was sent to the 2050 glazier companies in the sector. It contained questions on the awareness of the mechanical aids, the number of products that were purchased, and their use and expected effect on reduction of the musculoskeletal load. The same data were also gathered from the three participating companies as a reference. To determine differences between variables, a chi-square test with 95% confidence interval was used (Pearson’s test p < 0.05). It was applied to find relationships between • • •

The size of the company and level of investments The size of the company related to the adoption The opinion of users on physical load reduction

The satisfaction of regular users was determined at three levels: (1) satisfaction with the use of the device itself; (2) satisfaction with the new working method; and (3) satisfaction with the final result of the work. The 2050 glazier companies that received the questionnaire were members of FOSAG. The exclusion of nonmembers had a practical reason: we only had addresses of the members.

6.6 RESULTS 6.6.1

RESULTS

OF

STEP 2: ANALYSIS

The three main problems identified by the three glazier companies appeared to be loading and unloading panes on the car, horizontal transport and vertical transport, and removing putty. These issues were confirmed by the ergonomists who observed the work.

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6.6.2

RESULTS

OF

STEP 3: SELECTION

77

OF IMPROVEMENTS

A large list of solutions was developed in the solution sessions. Some were not feasible because of the large impact they would have. One solution that had large effects was to require architects to reduce the use of large windows. Some solutions were too costly, and some had only a minor effect. From the total list of solutions, the following were chosen to be tested in the three companies. •

• • • • •

•

An agreement was made with the glass manufacturers that all panes would be marked with a sticker to show the exact weight (in kg) of the pane, so that glaziers would not have to estimate the weight. For loading and unloading the pane from the truck, a special glass hoist was developed (Fig. 6.1). A glass cart (Fig. 6.2) was developed to reduce the loading during horizontal transport from the truck to the building. To reduce the loading during horizontal transport inside a building, a glass sledge was developed (Fig. 6.3). To reduce manual vertical transport, a special lifting device was designed that could be used in combination with scaffolding (Fig. 6.4). To eliminate all manual transport (vertical as well as horizontal), an existing truck with crane was adapted to transport both the glass and the glazier (Fig. 6.5). A mechanical putty remover was developed that reduced forceful handling (Fig. 6.6).

FIGURE 6.1 The glass hoist is a device that can be mounted on the glass truck to lift the pane from the truck onto the glass cart. (Photo courtesy of Muyen BV.)

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FIGURE 6.2 The glass cart is a device that enables horizontal transport without manually carrying the glass. (Photo courtesy of Muyen BV.)

6.6.3

RESULTS

OF

STEP 4: PILOT STUDY

WITH IMPROVEMENTS

Glaziers from the three pilot companies were satisfied with the solutions. Some minor revisions had to be made on handles and the position of the suckers. With respect to the truck-crane (Fig. 6.5), there was uncertainly regarding its safety. The question was whether it was stable and strong enough to carry the load of a pane together with a glazier in positions far away from the base of the truck. Therefore, it was decided to study this proposal further. Among the experts there was also uncertainty about the possibility of breaking glass with the transport devices. However, the response of all glaziers after the test was “We are used to working with glass, so we also know when to be careful.” The strength of the participatory approach was evident here.

FIGURE 6.3 The glass sledge is a device to transport glass on galleries and other flat surfaces. (Photo courtesy of Muyen BV.)

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FIGURE 6.4 To prevent manual lifting on two regular ladders, a special device to lift glass up the wall of a building has been developed. (Photo courtesy of Piet Ridder.)

6.6.4

RESULTS

OF

STEP 5: IMPLEMENTATION

All three companies decided to buy mechanical devices and paid attention to the preparation for using them. For instance, it was agreed that the transport of the devices to the construction site should be organized.

6.6.5

RESULTS

OF

DIFFUSION

AT THE

SECTOR LEVEL

About 80% of all companies visited the demonstration day. Most of them felt that the event and the mechanical aids displayed were useful (the impression of FOSAG, Arbouw, and TNO representatives who were there). A videotape given to the companies that attended was also sent to other members of FOSAG who did not visit the demonstration day. The solutions and a report of the day’s activities were published in several journals, including specialized publications of the construction industry.

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FIGURE 6.5 For vertical and horizontal transport of glass, as well as mounting the pane, this truck with crane can be effective. (Photo courtesy of Arbouw.)

6.6.6

RESULTS

OF THE

EFFECTS STUDY

AT THE

SECTOR LEVEL

The sector questionnaire was completed by 412 glaziers (response 20.1%), and 88% of the respondents were aware of the fact that new glazing devices were available. One or more of the devices was bought and used by 55% of them. The same group mentioned that the devices were not only bought (234 glass carts, 105 glass sledges, 66 glass hoists, and 50 vertical transport devices), but actually used as well. Two devices (truck with crane and mechanical putty remover) were not included in the research.

FIGURE 6.6 To reduce forceful handling, a mechanical putty remover is advised. (Photo courtesy of Fein GmbH.)

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100 80 60

412 companies PE companies

40 20 0 at least one

glass cart

glass sledge

glas hoist

device to lift

FIGURE 6.7 The percentage of participating companies adopting the PE approach compared to companies that were informed. At least one means at least one of the devices is bought and used.

The resources of companies to invest in new technologies have been determined. There appears to be a strong relationship (p = 0.000) between the size of a company and the number of devices bought, that is, the amount of the investment. Thus, small companies in general invest less than larger companies. However, larger companies need to buy relatively more devices than small companies because they employ more glaziers who use them. The three participating companies adopted a total of five glass carts, eight glass sledges, four glass hoists, and six vertical transport devices. Figure 6.7 shows a comparison between the adoptions of the three participating companies and the other respondents. The glazier companies that adopted one or more of the devices are shown as a percentage of the total number of respondents. The participating companies have all adopted at least one of each type of device, which is not true for the respondent group. The adoption rate for respondents varies from 10 to 41%. Reasons for these differences can be found in open questions of the questionnaire. The companies that did not buy the glass hoists or vertical transport devices reported that they did not have enough volume of business to invest in these devices. Among the companies that used the glass sledge, 44% used it weekly and 39% used the glass cart weekly. Large differences are found in the frequency of use of the glass hoists and vertical transport devices. Reduction of physical load and increased satisfaction has been determined for frequent users of the devices (31% of the respondents); 91% indicated a reduction of the physical load as a consequence of the mechanical devices used. Often (47%) a reduction in back loading is mentioned, but 92% report that this load reduction does not result in reduced sick leave. Furthermore, the significance of the reduction of physical load as a consequence of regular use of the devices has not been demonstrated (p = 0.23). With respect to the three levels of satisfaction (satisfied with the device, satisfied with the working method, and satisfied with the result of the work), significant improvement was demonstrated at all levels (Table 6.1).

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TABLE 6.1 Satisfaction with the Devices Satisfaction about Use of the device New working method Result of the work

% of users indicating very or sufficiently satisfied 86.3% 87.7% 92.6%

Pearson’s p .001 .026 .020

Satisfaction at all three levels by regular users has been demonstrated. In the open questions, the reason “handy to use” is often reported. However, use of the devices is difficult in some situations, such as on a rough ground or around trees in front of a building.

6.7 DISCUSSION Musculoskeletal discomfort among glaziers has been reduced because it is estimated that more than half of the glazier companies use one or more mechanical devices specially developed for reducing the musculoskeletal load. Also, the various partners, including FOSAG and Arbouw, consider the project to be successful. Since the participating companies regularly use the glass-handling devices and are highly satisfied with their use, the participatory approach seems to have succeeded in developing devices that are also suitable for nonparticipating glass companies. In our opinion, there were three major success factors (see also Bernoux 1994): 1. The fact that employees defined the needs and cooperated in finding and testing solutions 2. The fact that solutions were very simple to implement, visible, and easy to understand in their use (see also Rogers 1995) 3. The fact that a sector group was responsible for the process, including a campaign at the sector level Nevertheless, this study has three major weaknesses: 1. The efforts were great, and the question arises whether this is the most efficient way (including roles of the participants) to reduce musculoskeletal loading in a sector. 2. There was a low response on the evaluation questionnaire. In fact, we only know for sure that 11% of the glazier companies that are FOSAG members use the devices. 3. More adoption is possible because 45% of the respondents had not yet bought a device.

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Furthermore, it was not possible to carry out this study according to the rule of the experimental paradigm. Ideally, a control group of glazier companies that were excluded from the campaign would have been formed, but experiments in a naturalistic setting often have these constraints (Vink and Kompier 2003). Discussions with other the glazier companies revealed that important reasons for buying the new devices included better working conditions and (sometimes) efficiency improvement, partly due to the expected reduction in sick leave over the long term and partly because of lower direct costs (Koningsveld et al. 2004). For instance, the glass cart enables some work to be done by only two glaziers instead of three, which reduces labor costs. In a previous evaluation 3 months after ending the PE project (before the campaign), the participants reported moderate use of the devices (Jong et al. 2000). When this was again evaluated more than a year later, adoption by participating companies had increased significantly. All companies bought more devices. Furthermore, the frequency of use had decreased for the glass sledge and the glass hoist, but increased for the glass cart and the vertical transport device. Apparently, the devices that were adopted as a result of participation in the project pleased the glaziers in practice. As a result, more devices were bought. This shows that an evaluation should not be performed too early in the process because the time required for evolution in the use of the devices should be taken into account. The low level of response on the questionnaire could be improved by individual interviews or by stimulating the company management. However, the costs of these efforts are high and the results based on 412 questionnaires returned are already indicative. The number of companies not using the mechanical aids could be increased. The three companies actively involved in the PE approach received extra treatment, which may have led to a better adoption rate in those three companies (100% vs. 55%). This strengthens the power of PE approaches found in other studies (Bernoux 1994; Wilson and Haines 1997; Vink and Kompier 1997; Vink et al. 1997; Noro and Imada 1991). It appears that more direct involvement of employees is advised because it results in greater adoption of improvements.

6.8 CONCLUSIONS This case shows that a thorough, planned design process could lead to reduction of discomfort in an employment sector. More than half of the glazier sector works with at least one of the new devices. Important success factors include the employees defining the needs and testing the solutions, the solutions being clearly stated and highly visible, and the sector playing a large role in implementing the solutions.

ACKNOWLEDGMENT The authors want to thank FOSAG and SVEG for their support.

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REFERENCES Arbouw (1996) Risk Assessment in Transport and Mounting Glass Panes, Amsterdam: Arbouw (in Dutch). Bernoux, P. (1994) “Participation: A review of the literature.” In M. Gold, ed., The Economics of Participation, Dublin: European Foundation for the Improvement of Living and Working Conditions, 6–11. Jong, A.M. de and Vink, P. (2000) “The adoption of technological innovations for glaziers: Evaluation of a participatory ergonomics approach.” International Journal of Industrial Ergonomics, 26: 939–946. Koningsveld, E.A.P., Dul, J., Rhijn, J.W. van and Vink, P. (2004) “Enhancing the unpact of Ergonomic interventions.” In Ergonomic in the Digital Age. Proceedings of the 15th Triennial Congress of the International Ergonomics Association, Seoul (on CD-ROM). Noro, K. and Imada, A. (1991) Participatory Ergonomics, London: Taylor & Francis. Rogers, E.M. (1995) Diffusion of Innovations, New York: The Free Press. Urlings, I.J.M. (1996) Guide to Lighten the Load of Glaziers, Amsterdam: Arbouw (in Dutch). Urlings, I.J.M., Vink, P. and Wortel, E. (1994a) “A technique for finding solutions.” In Proceedings of the 12th International Ergonomics Association Congress, Toronto, Vol. 3: 352–354. Urlings, I.J.M., Vink, P. and van der Molen, H.F. (1994b) Scaffolding Guide to Lighten the Load, Arbouw: Amsterdam (in Dutch). Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics, 40(4): 435–449. Vink, P., Urlings, I.J.M. and van der Molen, H.F. (1997) “A participatory ergonomics approach for redesign work of scaffolders.” Safety Science, 26(1/2): 75–85. Wilson, J.R. and Haines, H.M. (1997) Participatory ergonomics.” In G. Salvendy, ed., Handbook of Human Factors and Ergonomics, 2nd ed., Chichester: Wiley, 490–513.

Discomfort 7 Reducing in Installation Work A.M. de Jong and P. Vink CONTENTS 7.1 Introduction ....................................................................................................85 7.2 The Company Studied in This Case..............................................................85 7.3 Health and Safety...........................................................................................86 7.4 The Approach.................................................................................................86 7.5 The Method ....................................................................................................87 7.6 Results ............................................................................................................88 7.7 Discussion ......................................................................................................91 7.8 Conclusions ....................................................................................................92 References................................................................................................................93

Parts of this chapter are reprinted from Jong, A.M. de and Vink, P. (2002) “Participatory ergonomics applied in installation work.” Applied Ergonomics, 33: 439–448. (Copyright 2002, with permission from Elsevier)

7.1 INTRODUCTION Incidence of sick leave and musculoskeletal discomfort among installation workers is high (Jong and Vink 2002). Installation work is done as part of construction and maintenance, and it could involve installing central heating, installing electrical systems, plumbing, or making regulation systems for the process industry. Part of this work is done in work stations at the company location, but mainly it happens at the construction sites. Conditions at these sites vary greatly. Often the work is done under time pressure because clients want to use the installed systems as soon as possible.

7.2

THE COMPANY STUDIED IN THIS CASE

In the case discussed here, an installation company wanted to reduce workers’ musculoskeletal discomfort and also improve work efficiency. This is one of the largest companies in the Benelux, with a staff of 7000 employees. The company intends to

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be the best in regard to quality and safety, and it is well equipped to do the more complex installation work. The strategy of the company is to acquire the more complex projects as well as the average projects. Another part of the strategy is to pay much attention to the workers because of their importance in the production process. The consequence of this strategy is that experienced and highly educated installation workers are needed, as well as a group of employees equipped to do the average projects. Attention is paid to training employees in new working methods but also to health and safety issues. The company has locations spread across several EU countries in order to serve the clients in the different regions and to have local employees close to the clients. Each location has a manager responsible for planning, product quality, and health and safety. This manager can employ specialists in the field of health and safety, and, in fact, a health and safety manager is working at almost every company location. The various locations often have work stations where the company’s work is done. If new systems are introduced, the work stations in the local workshops are redesigned. At construction sites the installation company’s influence on working conditions is very low because other companies own the site. The only influence management has is to pay attention to the optimal tools required to improve the work done by their installers.

7.3

HEALTH AND SAFETY

Work stations in the local offices and the work preparation stations are ergonomically well designed to speed up the work and increase quality. At the construction sites, the working conditions are worse because of the lack of company influence. Transport of materials and tools from and to the van is often done manually. Employees may have to work in a kneeling position, in limited space, or reaching above the head in a static posture. The major risks on these construction sites involve safety issues and concerns about excessive musculoskeletal loading. Safety risks include slippery surfaces and falls, as well as accidents involving electricity. The heavy manual lifting and carrying, static postures, and repetitive handling often seen on construction sites can create problems in regard to musculoskeletal loading. Before starting to reduce worker discomfort, a campaign designed to improve safety was conducted for 2 years.

7.4 THE APPROACH In a meeting, the president of the company emphasized the importance of improving worker discomfort levels to the company management and to health and safety managers. That session discussed a change of priority: After 2 years of paying attention to improving safety conditions, the next 2 years would focus on improving workers’ physical loading conditions. The president said, “For our company there are two main issues: making money and care for our employees that make the money. Therefore, in improving the physical discomfort and load we will have to look for those improvements that reduce the loading on our employees and increase efficiency in work.”

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The idea was that improvements were needed, especially in the work done on construction sites. After this session the staff was asked to develop a stepwise approach to implement improvements applicable at various construction sites. This was a positive consequence of the strategy to do both complex and average installation work and to pay attention to the employees. This chapter describes the design process and the effects of the project.

7.5 THE METHOD The design process consisted of six steps, based on previous experience (Vink and Koningsveld 1990; Jong and Vink 2000; Looze et al. 2001). •

•

•

Step 1: Preparation. The goal of the project was defined in this step, and a steering group responsible for following the process was formed. All employees were informed in the journal published by the companies, and every employee received a postcard specifying the project. Step 2: Analysis. In this stage the main musculoskeletal risks and hazardous tasks were defined. Those definitions were based on sick leave documents already available at the health and safety institutes; interviews with management, health, safety, and environment (HSE) managers, and employees; and previous studies. Step 3: Idea generation. Group sessions were planned to develop new ideas for improvements in the most hazardous tasks, according to procedures described in detail elsewhere (Urlings et al. 1994; Chapter 6). Three group sessions were planned: one on heavy lifting and carrying, one on kneeling work, and one on static work. The groups consisted of approximately 20 subjects, mainly employees, middle managers, and foremen, with some staff and an external ergonomist.

In the group sessions, the main problems were explained with videos and pictures first, and then all attendees wrote a solution on paper. These solutions were collected and presented (nobody knew who wrote which idea). After that process, a new solution round was introduced and additional ideas were collected. An estimate was made of the effect each solution might have on productivity, health, and feasibility. •

•

Step 4: Testing. The most promising ideas were assembled by employees, staff, or external experts. These were tested by a group of employees who were used to working together, and tasks were observed by the ergonomist; postures were videotaped and time of handlings was recorded under both the old and the improved working conditions. Musculoskeletal discomfort and worker productivity were estimated by observations and analyzing the videotapes. Step 5: Implementing. Solutions with positive effects were communicated throughout the entire company. This was done by making a solution book containing all the solutions, which was presented in meetings with the employees. Solutions particularly applicable to their work were given

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•

special attention. If a solution had a negative effect on at least one of the issues — musculoskeletal loading or productivity — it was not included in the book. Also, additional improvement ideas were requested and were added to the book when a commission (an external ergonomist, HSE experts, staff and management) approved the solution. This idea generation was promoted by giving prizes for the best solutions. Step 6: Evaluation. Based on interviews with health and safety executives in all parts of the company, the number of solutions bought was calculated. Also, the number of additional solutions and the the actual use of the improvements were estimated. The company then estimated costs and benefits of the total project.

7.6 RESULTS This section describes the results observed for each step. •

•

Results of Step 1 (Preparation). The defined goal of the project was not surprising: to reduce musculoskeletal discomfort and improve efficiency at construction sites. A more specific goal was needed, and it was decided to focus the goal more on the analysis step. Top management and the staff members involved in safety and health and communications agreed on this goal. Results of Step 2 (Analysis). The main problems were transport (heavy manual handling) to and from the van, working in a kneeling position, and working in static postures. The staff members mentioned in the

FIGURE 7.1 A draw-out workbench that eliminates working on the floor and reduces back flexion.

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FIGURE 7.2 A transport device to eliminate manual lifting and carrying.

•

previous step joined the TNO advisors to agree on the specific goal of reducing musculoskeletal discomfort and improving productivity in these three tasks. Results of Step 3 (Idea generation). Ideas were generated by 25 employees from various parts of the organization. From a large list of solutions, nine were chosen that were feasible and were estimated to contribute most to improving the problems. Four examples of these solutions are shown in Figs. 7.1 to 7.4.

FIGURE 7.3 A sitting device to eliminate kneeling during installation work on the floor.

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FIGURE 7.4 An easy-roll gets the spool onto a buck without lifting.

•

Results of Step 4 (Testing). The results of the tests on productivity and musculoskeletal loading are shown in Table 7.1. Most improvements resulted in a productivity increase; doing the same work with fewer employees in the new situation is seen as a productivity improvement. Most improvements also reduce the work load. It is assumed that reducing the duration of carrying, lifting, or an awkward posture reduces the risk and the discomfort.

TABLE 7.1 Number of Employees Needed in the Old and the New Situations and Percentage of Time Spent Carrying and Lifting (Lift); in a More Than 60° Flexed Back Posture (Flex); or in a Kneeling Position (Kneel) Number of employees Solution 1 2 3 4 5 6 7 8 9

Old 4 2 4 4 3 2 2 2 2

New 2 2 2 4 3 2 2 2 2

% of time lifting/flexed/kneeling Old 34% lift 6% lift 32% lift 14% lift 45% flex 23% flex 34% flex 45% kneel 31% kneel

New 6% lift 0% lift 3% lift 4% lift 7% flex 8% flex 12% flex 2% kneel 4% kneel

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TABLE 7.2 Estimation of the Benefits within 1 Year from Each of the First Four Solutions

Solution 1 2 3 4

Number of solutions in use 3 73 3 35

Reduction in man-hours/week 16 0.25 8 0.08

Reduction in man-hours (40 weeks) 1,920 730 960 117

total, 1–4

•

•

Cost reduction (€45/hour) 86,400 32,850 43,200 5,265 167,150

Results of Step 5 (Implementing). The nine solutions were included in a solution book, and every part of the company received copies that were used in meetings. Additional improvements were asked for in these meetings, which yielded another 60 proposed solutions. Twelve of these were expected to have a positive effect on productivity and health and were applicable in more than one part of the company, so these twelve ideas were added to the solutions book. Results of Step 6 (Evaluation). The number of additional solutions proposed was estimated to be 60, as noted in the previous step. In total, at least 138 devices were in use throughout the company. All of the nine chosen solutions were used at least weekly, and seven were used on a daily basis.

The cost/benefit ratio for the project was positive, according to the company. The investment consisted partly of man-hours (€50,000) and partly of buying new equipment (€14,060), for a total investment of €64,060. The benefits were especially favorable in solutions 1, 2, 3, and 4 (Table 7.2). The total reduction in costs generated by the first four solutions could be as much as €167,150. However, the experience of the company is that in practice, only roughly half of these reductions are realized. This means that the actual benefit is approximately €16,000 in 1 year, apart from the reduction in musculoskeletal discomfort and the improved wellbeing of employees.

7.7 DISCUSSION As a result of this project, worker discomfort should be reduced by using the new devices, and financial benefits will be felt within a year. From the company’s point of view, therefore, the project was a success. The company purchased 138 new devices and found 60 additional improvements. Probably more improvements could be found, but the solutions presented in this chapter were the only ones traceable by interviews. The implemented solutions contribute to reduction in discomfort and work load and improve well-being, as is mentioned by some workers, and the

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company estimates that there is a productivity increase with a return on investment of 25% (€16,000/€64,000). From a research point of view, however, the study is not a success. Only 198 solutions were generated by 7000 workers — a yield of just 3%. According to Rogers (1995) 2.5% of a group are innovators and adopt an improvement anyway. In this case, we could have reached only the early adopters. Also, the real effect of the improvements on musculoskeletal discomfort was not measured, and the effect of only the minimal number of improvements is known. For a good estimate, more indepth observations are needed. Furthermore, the evaluation was done within half a year after the project was completed. As noted in Chapter 5 and by Jong and Vink (2002), most improvements are implemented after 2 years because investments in new equipment first have to be put into a budget for the following year. A proposal for conducting a thorough evaluation was discussed with the company but did not interest them. It is not part of the company’s strategy to sponsor further scientific research. Such questions may be of more concern to governments. A previous study (Jong 2002) showed that six factors play an important role in successfully implementing improvements: 1. 2. 3. 4.

User tests by employees Improvements focused on the specific tasks Active participation of management in keeping more employees informed Direct participation of employees and opinion leaders in the improvement process 5. Good cost/benefit ratios 6. Usable products (without changing the work drastically) In this project all six factors played a role because the tests were performed by employees and the improvements were focused on the actual work. Costs and benefits were explicitly mentioned, and management supported the improvements. Perhaps the weakest point in this project was the direct participation. Of the 7000 employees, only 3% were directly involved. A thorough evaluation was not conducted, although it could have been helpful to the company as well as to the research. Such an evaluation could show that only a part of the company is involved in solutions and that more activities could be needed to spread the knowledge further. However, the company was not interested in a further evaluation because the project was seen as successful. Perhaps ergonomists should train themselves to be better change agents — better able to convince companies of the need for evaluation and further implementation of solutions.

7.8 CONCLUSIONS By using a participatory process, various improvements were implemented to reduce musculoskeletal discomfort and increase productivity in the installation company. The company evaluated the project as successful because it contributed to the company’s overall strategy. From a scientific point of view, it is difficult to draw

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conclusions as to the effects. More thorough research is needed, especially concerning the evaluation. Among the lessons learned from this project are: (1) that user tests by employees themselves are very important; (2) that the involvement of HSE managers is important; and (3) that explicit attention to costs and benefits is essential. Perhaps ergonomists should be better trained as change agents in order to convince companies of the usefulness of evaluation and further implementation of solutions.

REFERENCES Jong, A.M. de (2002) Improving Working Conditions at the Construction Site, Delft: Delft University of Technology (Ph.D. thesis, in Dutch). Jong, A.M. de and Vink, P. (2000) “The adoption of technological innovations for glaziers: Evaluation of a participatory ergonomics approach.” International Journal of Industrial Ergonomics, 26: 939–946. Jong, A.M. de and Vink, P. (2002) “Participatory ergonomics applied in installation work.” Applied Ergonomics, 33: 439–448. Looze, M.P. de, Urlings, I.J.M., Vink, P., Rhijn, J.W. van, Miedema, M.C., Bronkhorst, R.E. and Grinten M.P. van der (2001) “Towards successful physical stress reducing products: An evaluation of seven cases.” Applied Ergonomics, 32: 525–534. Rogers, E.M. (1995) Diffusion of Innovations, New York: The Free Press. Urlings, I.J.M., Vink, P. and Wortel, E. (1994) “A technique for finding solutions.” Proceedings of the 12th International Ergonomics Association Congress, Toronto: Vol. 3: 352–354. Vink, P. and Koningsveld E.A.P. (1990) “Bricklaying: A step by step approach to better work.” Ergonomics, 33(3): 349–352.

Discomfort 8 Reducing in Office Work P. Vink and M.A.J. Kompier CONTENTS 8.1 8.2

Reducing Discomfort in Office Work............................................................96 Ergonomic Interventions: Not Only What You Do, but Also How .................................................................................................96 8.3 The Case Company ........................................................................................96 8.4 A Participatory Approach ..............................................................................97 8.5 Three Studies and Three Research Questions...............................................98 8.6 Methods and Procedures................................................................................98 8.6.1 Study 1 ...............................................................................................98 8.6.2 Study 2 ...............................................................................................99 8.6.3 Study 3 ...............................................................................................99 8.7 Results of Study 1: The Old Workplace (n = 45) .......................................100 8.8 Results of Study 2: The Ergonomic Experiment (n = 12).....................................................................................101 8.8.1 The Self-Chosen Workplace ............................................................102 8.8.2 Comparing the Old Workplace and the Recommended Workplace.........................................................................................102 8.8.3 Comparing the Old, Recommended, and Self-Chosen Situations..........................................................................................103 8.9 Results of Study 3: The Follow-Up Study (n = 45) ...................................104 8.9.1 Comparing the Self-Chosen Situation and the Old Study (n = 45)..................................................................................105 8.9.2 Comparing Two Subgroups: Twelve and Thirty-Three Employees (n = 45) .........................................................................105 8.9.3 Answers to the Research Questions ................................................107 8.10 Conclusions ..................................................................................................108 Acknowledgment ...................................................................................................108 References..............................................................................................................109

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This chapter is based on Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics, 40(4): 435–449. See also http://www.tandf.co.uk/journals/tf/00140139.html

8.1

REDUCING DISCOMFORT IN OFFICE WORK

Work station design, the work tasks involved, and work–rest schedules (e.g., the scheduling of breaks) contribute to the type and prevalence of physical discomfort in offices. Physical discomfort in office work is quite common, as was demonstrated in a study by Fogleman and Lewis (2002). These authors studied discomfort in various body regions (head and eyes, neck and upper back, lower back, shoulders, elbows and forearms, and hands and wrists) and the way such discomfort was related to keyboard use and monitor and keyboard position. Fogleman and Lewis demonstrated that discomfort increased as a function of the number of hours the keyboard was used. They also showed that improper monitor and keyboard position were related to head/eye and shoulder/back discomfort, respectively. These results emphasize the importance of work station ergonomics, well-designed work tasks, and well-designed work–rest regulations. From these and comparable studies it also follows that ergonomic interventions in office work may be indicated as a means of increasing comfort (see also Mehkora et al. 2000).

8.2

ERGONOMIC INTERVENTIONS: NOT ONLY WHAT YOU DO, BUT ALSO HOW

Implementing ergonomic improvements is more than choosing the right ergonomic technical design solution. It is well known from ergonomic studies (e.g., Ong et al. 1988; Grandjean et al. 1983) that employees do not automatically adopt welldesigned office furniture, such as adjustable seats and desks. From studies in participatory ergonomics (Chapter 4) it may be concluded that ergonomic improvements are best implemented when employees themselves, as well as other company parties, are actively involved (Noro and Imada 1992; Imada 1994). Positive results have been obtained by using a stepwise participative approach (Chapter 4). This approach is based on the assumption that employees ought to be recognized as experts with respect to their own work situation and that organizational change is best developed in a participative and systematic way.

8.3 THE CASE COMPANY Against this background, an ergonomic intervention study in order to reduce physical discomfort was carried out at the Department of Salary Records in a Dutch national ministry. This department is responsible for paying salaries to all employees in this ministry, and the work is both mentally and physically demanding. It consists mainly of visual display unit (VDU) work (data entry, data control, word processing, data searching, reading documents, and so forth). Around the 15th of each month, all

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necessary changes need to be put into data files to enable proper payment of salaries. This resulted in an elevated work pace, especially in the 2 weeks preceding the deadline. Management of this department wanted to improve the work situation and chose to start an ergonomic project.

8.4

A PARTICIPATORY APPROACH

In the first phase of the project a steering committee was formed consisting of the head of the department (chairman), a representative of the health and safety committee, the company doctor from the ministry, an ergonomist, a representative of the personnel department, a representative of the union, and of the central occupational health service of the government. In addition, a small team (chairman, ergonomist, and employee) was formed to ensure daily progress. The ergonomist was an external consultant who also undertook the research and prepared the questionnaires and tests (Vink and Kompier 1997). From a LOQUEST questionnaire study (Hildebrandt 1992) it appeared that 39% of the 45 employees had neck complaints and 31% had shoulder complaints during the previous 12 months (Vink and Kompier 1997). These scores were significantly higher than those in two large reference groups of about 1000 Dutch employees (Fig. 8.1). These results were discussed in regular work consultation meetings. In these meetings it appeared that the employees preferred to focus on the improvement of the workplace in order to reduce neck complaints because these bothered them most during work.

60 50 40 30 20 10 0 shoulders

elbows

study population

wrists/hands

neck

maintenance workers

upper back

lower back

agricultural workers

FIGURE 8.1 Percentage of the 45 employees in the study population reporting complaints during the last 12 months in the study population, compared to Dutch reference groups in maintenance work (n = 436) (Hildebrandt et al. 1996) and in agricultural work (n = 1634) (Hildebrandt 1995).

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8.5

THREE STUDIES AND THREE RESEARCH QUESTIONS

This participatory ergonomics project consisted of three parts: 1. Ergonomic study of the old workplace First, the old workplace — that is, the work situation as it was at the start of the experiment — was investigated in the areas where all 45 employees worked. Research question 1 was: What is the ergonomic quality of the old workplaces in the department? 2. Ergonomic experiment Second, a sample of 12 employees participated in an ergonomic experiment. According to ergonomic guidelines, each of them was instructed to choose his or her ideal workstation and, after 2 weeks, was allowed to deviate from those recommendations. Objective and subjective effects were recorded. Accordingly, research question 2 included: (a) What differences can be shown between the recommended workplaces and the old workplaces? and (b) What differences can be shown between the recommended and self-chosen workplaces, and why would employees want to deviate? 3. Study of 45 employees (follow-up study) Third, on the basis of this experiment, all 45 employees received thorough and individual instruction in constructing their ideal workplace. Their workplaces and subjective reports were recorded 5 months later. Note that there was a difference between the 12 employees who participated in the ergonomic experiment and their 33 colleagues who did not. The latter group received thorough individual instruction and training only. It may thus be argued that the other 12 participating employees received an extra treatment. Accordingly, research question 3 included: (a) Is the workplace in the self-chosen condition a better workplace, compared to the old workplace? (b) Do the 12 employees who also participated in the previous experiment choose a better ergonomic design for the workplace compared to their 33 colleagues? and (c) Why do employees in the self-chosen workplace deviate from the recommendations?

8.6 METHODS AND PROCEDURES 8.6.1

STUDY 1

Anthropometric data were collected for each individual. In addition, various criteria were recorded for the old workplace: desk height; chair height; VDU screen position; keyboard position; availability of document holder; availability of an inclined desk; percentage of time carrying out VDU work; the position of the VDU screen with respect to light sources; foot space and foot rests; user-friendliness of software and documents to be handled; and the position of telephones, reference books, and records.

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99

STUDY 2

Next, 12 employees (7 men, 5 women) were selected. Criteria for inclusion were variation over workrooms, employees frequently performing “normal and representative tasks,” performing the same tasks over a period of at least 30 minutes, and motivation to participate in the experiment. Each of these 12 employees took part in the ergonomic experiment that was performed at the actual workplace. The subjects were recorded during normal VDU work, which included 30 minutes continuously sitting in a static posture in the traditional workplace, in the recommended workplace, and in a selfchosen workplace adjustment (2 weeks later). Lateral photographs were used to study the influence of the workplace adjustments on the neck and back position with respect to the vertical. The camera (135mm focus) was positioned at shoulder height, 0.2 m posterior to the table edge and approximately 3 m lateral to the subject. Three lateral photographs were made of each subject, in each condition, while the subjects were watching the screen (e.g., data controlling) in cases where this was the major part of the task. In cases where the major part of the task was looking at the document holder (e.g., data entry), the photograph was made during that part of the task. A vertical reference (doorpost or windowframe) was established in the background of the photograph. A line was drawn between the point of the nose and the middle of the ear cavity (the angle between the head and the vertical: neck flexion) and a line was drawn between the middle of the shoulder and the middle of the hip (flexion of the back). The average angle for the 12 subjects was calculated for both the old and the recommended conditions, and the differences were tested (t-test for paired observations, p < 0.05). This was also done for those subjects for whom detailed data were available in all three conditions. Six subjects were recorded in the old situation in the morning and again in the afternoon in the recommended situation. The other six were recorded in the recommended situation in the morning and in the old situation in the afternoon. The selfchosen workplace was recorded 2 weeks later, half of the subjects in the morning and half in the afternoon. Local musculoskeletal discomfort in 40 different body regions (summing up to seven cluster scores) was recorded in all three conditions (old, recommended, and selfchosen), using local postural discomfort (LPD) (Chapter 2). Before and after working for 30 minutes, subjects had to rate their perceived discomfort on a category ratio scale ranging from no discomfort (score 0) to extreme discomfort (score 10). For each employee, the difference in scores between before and after were calculated by subtracting the before scores from the after scores. The differences between the conditions were tested by the Wilcoxon signed-rank test for paired observations (p < 0.05).

8.6.3

STUDY 3

There were 45 subjects in the follow-up study (19 men, 26 women). The men’s average height was 1.78 m (SD = 0.08) and their average weight was 76 kg (SD = 7.6). For the women, the average height was 1.63 m (SD = 0.09) and the average weight was 63 kg (SD = 8). All of these employees received tailor-made instructions and training with respect to their ideal workplace. This instruction was based on the

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experiment with the 12 subjects mentioned earlier and was provided by the ergonomist and a trained employee, that is, an employee of the department who was trained in ergonomics by the ergonomist. After 5 months, data for the self-chosen workplace were recorded for each employee. The working conditions were observed and a questionnaire was used to evaluate whether improvements were actually implemented. The observed variables were chair height adjustment, table height adjustment, VDU screen position adjustment (both height and position on the table), keyboard position adjustment, the addition of a document holder, and the addition of an inclined desk. The questionnaire contained questions about the positive effects of workplace adjustments on back and neck complaints (Hildebrandt 1992).

8.7

RESULTS OF STUDY 1: THE OLD WORKPLACE (n = 45)

Figure 8.2 presents a typical workplace found before the intervention. From an ergonomic point of view, the old workplace was of poor quality. The old work stations in the department consisted of desks with a fixed, flat top 730 mm above the floor and swivel desk chairs with height-adjustable seats. The screen was usually positioned on the desktop in the right or left corner opposite the subject, and the documents were positioned left or right of the keyboard on the desktop. Keyboards were found in different positions. Extra adjustments such as document holders, screen holders, or desk inclinations were not available.

FIGURE 8.2 Typical work situation found in the old (i.e., preintervention) situation (note the flexed neck and the VDU screen that is not anterior to the subject).

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101

RESULTS OF STUDY 2: THE ERGONOMIC EXPERIMENT (n = 12)

Study 2 involved the recommended workplace. In order to improve the out-of-date work stations, adjustable furniture was necessary. The department had planned to order these new desks and chairs 5 years later, but the steering group advised management to order the new furniture right away. Management followed this advice. The department made an additional budget available for extra adjustments (document holders, inclined desks, foot rests, and screen holders). A recommended work station was established for each of the 12 employees (7 men, 5 women), based on ergonomic guidelines. The following improvements, (a) through (f), were chosen because they have a favorable effect on the neck, which was perceived to be the largest problem. a. Optimal seat height The optimal seat height was calculated by a procedure described earlier by Verbeek (1991). Using a ruler, the distance from the top of the desk to the sole of the shoe was measured while the subject sat on the desk with shoes on and fully clothed — the so-called popliteal height (Dainoff and Dainoff 1987). The seat height was adjusted to this popliteal height while the subject sat on the chair with a compressed seat spring (Fig. 8.3). b. Optimal desk height While the subject was seated on the desk, the distance from underneath the maximally flexed elbow to the top of the desk was measured, this being the elbow height. The table height was adjusted to equal the sum of the popliteal height and the elbow height (Verbeek 1991) (Fig. 8.3). c. Using a document holder A document holder was placed as close to the screen as possible, the viewpoint at the same height as the viewpoint on the screen. d. Screen height The viewpoint on the screen should be 100 mm below eye height (Delleman and Berndsen 1992).

2

1

FIGURE 8.3 Measurement of seat height (1) and desk height (1 + 2).

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e. Position of screen Since the main task for the 12 subjects was VDU work, the screen was placed in front of the employee. f. Position of the keyboard The keyboard was positioned in front of the subject so that the elbow angle was 90 degrees and the wrist was in an approximately neutral position.

8.8.1

THE SELF-CHOSEN WORKPLACE

After working for 2 weeks in the recommended workplace, the 12 subjects were asked to choose the work situation that they preferred. This self-chosen workplace resembled the recommended workplace, although several employees had changed their recommended workplace. Seat height (a) and desk height (b) were as recommended, except for one employee. She was a very small person with a managerial position and, while seated at the desk, had to talk with colleagues who stood in front of her. Her opinion was that extending her neck during the discussions would be uncomfortable and not in keeping with her status, so she raised the height of her desk and chair. She also added a footrest. Four employees, who also had to use large-format documents that could not be placed on a document holder (c), did not always use the document holder. The middle of the screen was positioned at about 100 to 200 mm below eye height. Most employees occasionally had to look at the keyboard and placed the screen height (d) somewhat lower than the recommended 100 mm to diminish nodding. The screen and keyboard were placed as recommended (e, f).

8.8.2 COMPARING THE OLD WORKPLACE THE RECOMMENDED WORKPLACE

AND

The position of the subject’s head was significantly different between the old workplace and the recommended workplace. It was closer to the upright position (Table 8.1) in the recommended workplace. This effect was not significant for the trunk position; the local perceived discomfort in the neck region was influenced most (Table 8.2;

TABLE 8.1 Mean Difference in Angle between the Old and the Recommended Situation Head position Trunk position

Difference 5.05 4.10

SD 7.64 8.55

T-value 2,29 1,66

* p < 0.05; t-test for paired observations, n = 12.

P-value* 0.021 0.062

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TABLE 8.2 Mean Difference in Local Perceived Discomfort between the Old and the Recommended Situation Difference 3.1* 0.1 1.2 3.2*

Neck Shoulder Back Total

Z-value 2.28 0.47 1.41 2.28

P-value* 0.01 0.32 0.08 0.01

* significant; p < 0.05; Wilcoxon signed-rank test, n = 12.

Fig. 8.4). Discomfort in the back also decreased, but this effect did not reach significance. The recommended situation had almost no influence on discomfort in the shoulder, but total discomfort significantly decreased.

8.8.3 COMPARING THE OLD, RECOMMENDED, AND SELF-CHOSEN SITUATIONS Data from only six employees could be used for comparing the self-chosen condition to the two others. Two subjects were absent but performed the experiment 1 week later, after the deadline of the 15th. Their data were not included because the task they performed a week later differed too much from that in the other two conditions. The data of three other employees were omitted since it appeared that 7 6 5 4 old 3

recommended

2 1 0 −1

neck

shoulder

back

total

FIGURE 8.4. The LPD in different body regions under both the old and the recommended workplace conditions (n = 12). The total is the sum of LPD numbers for all 40 regions, including the three regions mentioned in the figure.

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TABLE 8.3 The Mean Difference in Local Postural Discomfort Summed for All Regions Old vs. recommended Old vs. self-chosen Recommended vs. self-chosen

Difference 4.92* 3.75* 1.17

Z-value 2.2 1.9 0.1

P-value* 0.01 0.02 0.46

* significant; p < 0.05; Wilcoxon signed-rank test, n = 6.

they did not have identical work for half an hour, as a result of too many unexpected telephone calls. One employee had a sports injury to the knee and therefore sat asymmetrically. The remaining six subjects who were tested in the old, recommended, and self-chosen situations showed no significant differences (p < 0.05) in head posture (Table 8.2). Despite the small number of subjects, the total postural discomfort in the selfchosen and recommended situations differed significantly from the old situation (Table 8.3). The recommended and self-chosen situations did not differ significantly.

8.9

RESULTS OF STUDY 3: THE FOLLOW-UP STUDY (n = 45)

At this stage it was concluded that the recommended workplace constituted a clear improvement over the old workplace. Still, this experiment was the basis for several adjustments that were made at the next stage: instructions to the 45 employees in the department. Recommendations (a) seat height, (b) desk height, (c) document holder, and (e) screen in front remained unchanged. Recommendations (d) middle of the screen and (f ) keyboard were adapted. Recommendation (d) was set to 100 to 200 mm below eye height, but recommendation (f ) unfortunately was not included in the instruction because of a technical mistake. Based on this guideline, the ergonomist discussed the necessary accessories (document holders, inclined desks, screen holders, etc.) with every employee separately. Adjustable chairs and tables were ordered and a list of accessories to be ordered was made. Ordering the chairs, tables, and accessories took a long time because the purchasing department was not involved in the participatory ergonomics process and was not immediately convinced of their necessity. After the accessories were delivered, the ergonomist and the trained employee visited each employee. The three individuals transferred every employee’s old workplace to their recommended workplace. Before the move, a brochure entitled “How to Adjust My Workplace,” which contained the instruction mentioned earlier, was handed out.

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TABLE 8.4 Percentage of Employees Who Adjusted the Work (n = 29) and Percentage of Employees with Back or Neck Complaints (n = 18) Who Report a Positive Effect of These Adjustments on Back and Neck Complaints

Chair height adjustment Table height adjustment VDU screen position adjustment Keyboard position adjustment Addition of document holder Addition of inclined desk

8.9.1 COMPARING STUDY (n = 45)

THE

Workers with adjustments (%) 73 83 69 34 14 31

SELF-CHOSEN SITUATION

Workers reporting positive effects (%) 67 67 50 11 17 11

AND THE

OLD

Five months after the changes in work stations, data for the self-chosen workplace (that is, the workplace as it was at that moment in time) were recorded for every employee. Twenty-nine employees completed a questionnaire with respect to the actual implementation and the possible effects on back and neck complaints (four subjects did not work in the department any more, five were ill, three were on holiday, and four were not able to complete the questionnaire due to work commitments). Almost all (97%) of the twenty-nine employees had changed their work station. Table 8.4 summarizes the adjustments. Eighteen of the twenty-nine respondents had previous back and neck complaints, whereas eleven others did not. Table 8.4 also shows how many of these eighteen employees reported positive effects of the workplace adjustments on back and neck complaints. Table height, chair height, and VDU screen position were improved most often. Keyboard position was changed by only one third of the employees, probably due to the fact that this recommendation was omitted by mistake from the “How to Adjust My Workplace” brochure. Most employees with back and neck complaints considered these complaints to be reduced by the adjustments made, especially the adjustments to the chair, table, and VDU screen position. Figure 8.5 shows the percentages of employees reporting musculoskeletal complaints during the 12 months before and after the project. It is clear that the number of musculoskeletal complaints was reduced. The reduction in neck, high-back, and shoulder complaints is significant (t-test for paired observations, p < 0.05). The change in lowback complaints is not significant, nor was sick leave influenced significantly. However, a year after the study the management reported a 1% reduction in sick leave percentage, from 7 to 6%.

8.9.2 COMPARING TWO SUBGROUPS: TWELVE EMPLOYEES (n = 45)

AND

THIRTY-THREE

Figure 8.6 shows the differences in workplace adjustment between the 12 employees who also participated in the previous experiment and the 33 others, who only received

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50

40

30 before after 20

10

0 neck

upper back

lower back

shoulder

FIGURE 8.5 The percentage of workers reporting complaints during the 12 months before and after the project (n = 29).

thorough individual instructions and training. Those employees who also participated in the experiment show the fewest deviations from the recommended workplace. The differences in adjustment between the 12 employees who participated in the ergonomic experiment and the other 33 are significant with respect to desk height,

inclined desk document holder keyboard position screen position chair height desk height 0

20

40 12 in test

60

80

100

120

33 others

FIGURE 8.6 Percentage of the employees that adapted the workstation: the 12 employees that participated in the ergonomic experiment compared with the other 33.

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chair height, screen position, and keyboard position (t-test for paired observations, p < 0.05). From an ergonomic point of view, the 12 appear to work in better work stations. Between the two groups, the difference as to keyboard position adjustment is striking. It seems to illustrate that the 12 were carefully instructed to adjust their keyboard position, whereas the others were not. Why did the employees deviate from the recommendations? Table 8.5 shows that there are various reasons why employees deviate from the ergonomic recommendations. A major reason for deviating is related to specific task requirements (using A3 format, often rising from the chair, etc.).

8.9.3

ANSWERS

TO THE

RESEARCH QUESTIONS

Answers to the three questions that were raised earlier can now be summarized as follows: • •

•

Study 1/Question 1 From an ergonomic point of view, the old workplace was of poor quality. Study 2/Question 2 In the ergonomic experiment, clear improvements were demonstrated in the recommended situation when compared to this original situation, both with respect to the head position and with respect to the total perceived discomfort and local perceived discomfort in the neck region. From the ergonomic experiment it also appears that when allowed to deviate from the recommended workplace, employees may choose individually preferred solutions by reason of specific task demands (e.g., document handling, communication) and individual characteristics (e.g., height). Still, from a discomfort point of view, these individual preferences add up to a clearly better workplace than the old workplace. Study 3/Question 3 From the larger (n = 45) study, the self-preferred workplace appears to be better than the old workplace in terms of ergonomic standards (97% had changed their work station) and in terms of self-reports and musculoskeletal complaints. Most employees with back and neck complaints considered them to be reduced, especially as a result of adjustments to the chair, desk, and VDU screen position. From an ergonomic point of view, those 12 employees who also participated in the ergonomic experiment (Study 2) chose a better selfpreferred workplace than their 33 colleagues did. The difference between the group of 12 employees and the other 33 employees suggests that taking part in an ergonomic experiment in a naturalistic setting performs the role of an extra treatment. It leads to a better ergonomic adjustment compared to the condition in which employees only receive thorough individual instruction and training.

Thus, close employee participation seems to be very important in reducing physical discomfort. On the other hand, it does not seem to be necessary to carry

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TABLE 8.5 Why Employees Choose to Deviate from Ergonomics Recommendations with Respect to a Workplace Adjustment n 2 2 2 2 3 3 5 5 7

Motivation Table height is too low for my status. A high table does not correspond aesthetically to that of my colleague. A high screen hinders communication with my opposite colleague. My screen height is higher because I like to think while sitting back and looking at the screen. It takes too much time to use a document holder. I can rise faster from a higher chair. The screen height feels uncomfortable, so I put it lower. A document holder is not easy to use with large documents (e.g., A3). We do change the height of the chair dependent on the task.

(Only arguments mentioned twice or more are reported here.) (n = number of employees)

out an ergonomic experiment in order to have employees improve their work stations. The work stations of the employees who did not take part in the experiment were also significantly improved in comparison to the old ones. From the comparisons between the self-chosen and the recommended work situations — questions 2(b) and 3(c) — it follows that employees may have good arguments for deviating from that which is ergonomically best. In both Studies 2 and 3, employees could very well describe their reasons for deliberately changing the recommended layout, and they were even aware of the fact that it would increase their discomfort (Table 8.5).

8.10 CONCLUSIONS This study demonstrates that it is possible to reduce discomfort in office work. If the employer provides well-designed office equipment and if, in a participatory approach, employees are carefully instructed and trained in its utilization, employees may choose a better adjustment of their workplace. However, they may not accept the adjustment recommendations in all cases. An important reason for deviating from the ergonomic recommendations is related to specific task requirements. Still, from an ergonomic point of view, the self-chosen situation appears to be a much better condition than the traditional work situation. Experimental measurements in a naturalistic setting may contribute significantly to workplace improvements, (1) by presenting adequate and “objective” information for workplace improvement and ergonomic redesign, and (2) as a change agent itself, that is, as an “intensified treatment.”

ACKNOWLEDGMENT The authors want to thank the Dutch Ministry of Home Affairs for their contributions.

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REFERENCES Dainoff, M.J. and Dainoff, M.H. (1987) A Manager’ s Guide to Ergonomics in the Electronic Office, Chichester, UK: Wiley. Delleman, N.D. and Berndsen, M.B. (1992) “Computer aided postural analysis on optimum workstation adjustment for VDU operations.” In M. Mattila and W. Karwowski, eds., CAES’ 92, Amsterdam: Elsevier, 345–352. Fogleman, M. and Lewis J.R. (2002) “Factors associated with self-reported musculoskeletal discomfort in video display terminal (VDT) users.” International Journal of Industrial Ergonomics, 29(6): 311–318. Grandjean, E., Hunting, W. and Piderman, M. (1983) “VDT workstation design: Preferred settings and their effects.” Human Factors, 25: 161–175. Hildebrandt, V.H. (1992) “Development of a software package questionnaire on musculoskeletal load and health complaints.” In M. Hagberg and Å. Kilbom, eds., International Scientific Conference on Prevention of Work-related Musculoskeletal Disorders PREMUS, Sweden, May 12–14, Book of Abstracts (Arbete och halsa, Solna): 123–127. Hildebrandt, V.H. (1995) “Musculoskeletal symptoms and workload in 12 branches of Dutch agriculture.” Ergonomics, 38: 2576–2587. Hildebrandt, V.H., Bongers, P.M., Dul, J., Dijk, F.J.H. van and Kemper H.C.G. (1996) “Identification of high-risk groups among maintenance workers in a steel company with respect to musculoskeletal symptoms and workload.” Ergonomics, 39: 232–242. Imada, A.S. (1994) “Overcoming cultural barriers within organizations.” In G.E. Bradley and H.W. Hendrick, eds., Human Factors in Organizational Design and Management IV, Amsterdam: Elsevier, 625–630. Mekhora, K., Listonc, C.B., Nanthavanijd, S. and Coleb, J.H. (2000) “The effect of ergonomic intervention on discomfort in computer users with tension neck syndrome.” International Journal of Industrial Ergonomics, 26(3): 367–379. Noro, K. and Imada, A. (1992) Participatory Ergonomics, London: Taylor & Francis. Ong, C.N., Koh, D., Phoon, W.O. and Low, A. (1988) “Anthropometrics and display station preferences of VDU-operators.” Ergonomics, 31: 337–347. Verbeek, J. (1991) “The use of adjustable furniture: Evaluation of an instruction programme for office workers.” Applied Ergonomics, 22: 179–184. Vink, P. and Kompier, M.A.J. (1991) “Participative ergonomics. An intervention strategy for reducing musculoskeletal injuries.” In Y. Quéinnec and F. Daniellou, eds., Designing for Everyone: Proceedings of the 11th Congress of the International Ergonomics Association, London: Taylor & Francis, 1699–1671. Vink, P. and Kompier, M.A.J. 1997 “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics 40(4): 435–449.

9 Productivity and Discomfort in Manual Assembly Operations J.W. van Rhijn, M.P. de Looze, L. Groenesteijn, M.D. Hagedoorn-de Groot, P. Vink, and G.H. Tuinzaad CONTENTS 9.1 Discomfort in Assembly ..............................................................................111 9.2 Market Demands Productivity Increase.......................................................112 9.3 Tools to Support Manufacturing..................................................................112 9.4 The Faber Case ............................................................................................117 9.5 The Original Situation .................................................................................117 9.6 The Improvement Process............................................................................118 9.7 Unique Possibility ........................................................................................120 9.8 The Evaluation .............................................................................................120 9.9 Results of the Six Steps ...............................................................................121 9.10 Results of the Evaluation .............................................................................124 9.11 Discussion ....................................................................................................126 9.12 Conclusions ..................................................................................................127 Acknowledgment ...................................................................................................127 References..............................................................................................................127

Parts of this paper are submitted for publication in the International Journal of Production Research.

9.1

DISCOMFORT IN ASSEMBLY

Two major issues play a role in manual assembly operations: increasing productivity and increasing health. For a company, it is essential to have efficient operations (Yamada 2002). Handling operations such as searching and walking add only a limited 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

111

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value to the product and should be avoided, and the handlings involved in making the product should be as short as possible (Yamada 2002). Work should be healthful, and stress and musculoskeletal injuries should be prevented (Yamada 2002). There is much room for improvement. Chapter 1 reveals that more than one third of the European working population has musculoskeletal problems developed during working. Improvement could be achieved by optimal postures and optimal mental loading, as well as by a good variation between static and dynamic activities. If dynamic activities are impossible, the optimum work–rest scheme to achieve good productivity and health could be found (Matthiassen et al. 2002; Sauter and Swansson 1991). Because discomfort is a predictor of musculoskeletal injuries, as noted in Chapter 2, the discomfort factor is often used in experiments to design the optimal layout and work–rest schedules.

9.2

MARKET DEMANDS PRODUCTIVITY INCREASE

Assembly work is under economic pressure (Eijnatten 2002). To survive in worldwide competition, companies are forced to produce ever-increasing volumes at the same costs. Meanwhile, the variety of products increases, shorter delivery times are demanded, and quality must be kept high as well. This pressure on the companies is likely to increase the pressure on the workers. Under these circumstances, the main problems of assembly companies are the logistics of producing the increased volumes per unit of time, the lack of space to run the assembly processes, and getting a healthy and motivated work force. For many companies, the traditional assembly concepts that were successful for many years no longer meet the need. These companies are challenged to find new concepts to solve simultaneously the logistic, spatial, and human factor problems.

9.3

TOOLS TO SUPPORT MANUFACTURING

To support innovation in manufacturing, a participatory and integrative approach was developed by TNO Industrial Technology in cooperation with TNO Work and Employment. This approach aims at reducing the lead time and the improvement of the worker’s job (Rhijn and Tuinzaad 1999; Tuinzaad et al. 2000). Important elements of the approach are the active participation of the company and the integration of two disciplines: assembly engineering and ergonomics. The approach proved to be successful in several cases (Tuinzaad el al. 2000). A part of this participative and integral approach was developed in depth. The ergonomics aspects as well as sociotechnical elements and ICT couplings were developed further in a project PSIM. PSIM stands for Participative Simulation environment for Integral Manufacturing enterprise renewal. In PSIM, both a procedure and dedicated software were developed and tested in five companies in Europe (CRFiat, Finland Post, and Volvo), Japan (Yamatake), and the United States (Ford). The PSIM participative simulation prototype supports companies in developing new organizational structures and technology in which humans can perform healthier and better. The companies evaluated PSIM positively as a breakthrough innovation in the field of business and work (see Framework PSIM).

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FRAMEWORK PSIM PSIM (Eijnatten et al. 2002; Vink et al. 2002) is short for Participative Simulation environment for Integral Manufacturing enterprise renewal. The goal of the project is to develop a system that facilitates improvement in production. The system consists of software and a procedure that can be applied by assembly companies. It was developed by TNO (The Netherlands); RWTH (Denmark); Chalmers (Sweden); TU/e (The Netherlands); FIOH (Finland); Baan (The Netherlands); GFI (Italy); and L.A.R. (Germany). The PSIM prototype that was put to a test consisted of the following six important parts: • • • • • •

Procedure: a stepwise approach to support a company in applying PSIM ergoTool: software including the latest guidelines to evaluate the load on the operator and to test effects or ideas for improvement STSD (Socio-Technical Systems Design) tool: software that helps a group arrive at a socio-technically sound organizational structure Navigator: software that supports end users in finding the right software tool Ontology: a language that supports modeling of the enterprise using information and communication technology (ICT) models Integrator: software that extracts data from the enterprise resource planning (ERP) system to test effects of improvement ideas

These six parts were tested in five companies (Table 1). Not every part was tested in every company because individual companies had their own interests and opportunities. The prototype was tested in work sessions. The test

TABLE 1 Summary of the Parts of PSIM Tested in the Various Companies Procedure

ergoTool

CRFiat

±

±

Finland Post

±

+

+

Volvo

+

+

+

Yamatake

±

+

Ford

±

+

Test site

STSD tool

Navigator

Ontology

Integrator

+

± = partially tested as far as possible or as far as required by the test site + = complete test Empty cell = not tested Grey cell = focus of the test

± ± ±

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groups produced an enormous number of ideas for manufacturing improvement, part of which were implemented immediately. The others were evaluated for later implementation. After the prototype test, a focus group session was organized with the management of the companies and some researchers from the PSIM group to discuss the main results and to assess positive and negative points. The results are presented for each company separately.

RESULTS CRFIAT The test proved that efficiency in design could be achieved by applying PSIM. Some ten persons from the company and five PSIM researchers participated in the test session. Navigator was found to be very useful because it allows parallel work in the design process. Engineers, managers, and designers can do their work on the same design simultaneously, and proposed changes are noticed by the other users immediately. However, Navigator should be further developed in order to be easier to use. ergoTool was seen as very helpful and complete, so this tool will probably replace the existing ergonomic analysis systems in this company.

FINLAND POST This post-sorting company also developed a large number of ideas for improvement that will result in higher productivity and more satisfied employees. In the test session, some 35 persons from the company and 12 PSIM researchers participated. The most important benefit was the participative test of the tools, especially ergoTool, because it indicated specific improvement opportunities based on numerical data regarding safety, lifting, and pushing and pulling (Fig. 1). The company found the criteria of the STSD tool also highly useful because they plan to set up self-managing teams in the future and now know the effects. A great advantage of the participative character of the PSIM game was that more persons were opening up and ready for improvement. Another benefit mentioned is that more aspects can be evaluated simultaneously. That is important because sometimes, for example, an improvement for lifting will conflict with a measure of task rotation. The integral character of PSIM allows for finding optimal solutions, instead of suboptimizations. A side effect of the test was that the discussions about Integrator helped the company in choosing an appropriate ERP system.

VOLVO CAR SYSTEMS Applying PSIM generated a large amount of ideas for improvements. Some parts of the ideas were implemented, which resulted in productivity increase and more satisfied employees. Also, the musculoskeletal loading was reduced.

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FIGURE 1 An example of a software screen used in sessions with workers.

In the test session also some 35 persons from the company and 12 PSIM researchers participated. The companies’ perspective of the PSIM prototype test was that they had learned a lot because they had to take in all the different aspects in building a new assembly line. Thanks to the test, more attention is now being paid to socio-technical issues. The procedure was evaluated positively because the operators involved in the tests appreciated the fact that they were being taken away from their normal work and were allowed to think on a higher level and learned more about the topics discussed during the tests.

YAMATAKE Ten people from Yamatake’s printing circuit board department in Japan and three researchers from Europe’s PSIM were involved in the test. The most important benefit for the company was the participatory procedure that fit extremely well into the company’s culture. Regarding ergoTool, the operators were used to working with more qualitative systems, whereas with the PSIM prototype more quantitative analysis is possible. The Japanese company considered this process to be very worthwhile because young employees will feel the need for more quantitative data in the future as a result of globalization. Also, Ontology was seen as very valuable for modeling the enterprise in ICT.

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FORD Eight people from the U.S. automotive company and three researchers from Europe’s PSIM were involved. The PSIM participative approach was not natural for this company, probably because the unions play such an important role. For instance, rotating between tasks is difficult because the unions could demand more salary. The ergoTool test resulted in a long list of improvement requests.

GENERAL RESULTS

FROM THE

END DISCUSSION

In most test sites the PSIM procedure proved to play an essential role in administering participative simulation. The steps of analyzing the existing situation and discussing ideas for improvement with groups of engineers, operators, management, and designers were both evaluated positively. In evaluating the PSIM procedure, companies mentioned that a facilitator is very much needed along with the software. The Ergonomic and STSD experts proved to be essential in the process of inviting the users to follow the procedure and in explaining some background of the PSIM. Also, the visualization support (by use of embedded videos) was evaluated positively. The following similarities and differences were observed among companies: • •

•

•

Companies that were not used to applying ergonomics evaluated ergoTool more positively then those who already were. The application of the mental-workload module, in ergoTool, and the application of the STSD tool resulted in the largest number of improvement ideas. Both tools were evaluated very positively. Other parts of the tools were evaluated as being “nice toys,” but whether they would replace existing checklists, methods, and software that were already in use by the test companies was questioned. Finally, it was mentioned that the application of the STSD tool was rather time-consuming.

REFERENCES Eijnatten, F.M. van, ed., 2002 Intelligent Manufacturing through Participation: A Participative Simulation Environment for Integral Manufacturing Enterprise Renewal, TNO Arbeid, Hoofddorp, The Netherlands: The PSIM Consortium. Vink, P., Eijnatten F.M., van and Rhijn G. van 2002 “Participation: A key for intelligent manufacturing.” In B. Stanford-Smith, E. Chiozza, and M. Edin, eds., Challenges and Achievements in E-business and E-work, Part 2. Amsterdam: IOS, 1328–1335.

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FIGURE 9.1 One of the products produced at Faber.

9.4 THE FABER CASE This chapter gives an example of designing an optimal production layout using discomfort as a parameter to predict health and also using a participative and integral approach developed by TNO. This participative approach was developed based on TNO experience in several projects, but appeared to be congruent with theories found in the literature (chapter 4; Looze et al., 2001; Rhijn et al., 2002) and the project PSIM (see Framework PSIM). Apart from the participative character, knowledge of the organizational, logistics, and technical aspects of production engineering was also included (Tuinzaad et al. 2000). This approach was applied in Faber Electronics BV, a company producing emergency exit lights (Fig. 9.1). This company experienced an increase in market demand, and to cope with these demands the final assembly of the lights had to be renewed. In the final assembly stage, the electronic unit and other components such as the tube luminescent (TL), the reflector, and the battery are assembled and packed.

9.5

THE ORIGINAL SITUATION

In the original situation the lights were assembled at large tables in batches of 60 products (Fig. 9.2). Per batch, two persons are working at two sides of the table. Their work comprises fetching the first components, spreading 60 of them out across the long table and assembling the first components. These activities are repeated for the second component. This pattern continues until the final component is assembled and the product is packed. This work pattern requires much walking, especially if larger components are involved, of which only a few can be held in the hand. The products are packed in carton boxes and placed on a pallet, a process that includes manual lifting.

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FIGURE 9.2 The old situation of assembling 60 products batchwise.

9.6

THE IMPROVEMENT PROCESS

The approach is based on previous experience with the participative and integrative approach (Tuinzaad et al., 2000) having elements of the PSIM procedure. (see Framework PSIM). Six steps are followed to arrive at a higher level of productivity and health in the assembly operations. 1. Preparation (Step 1) The first step is the initialization of a multidisciplinary working group within the company and defining the goal. This small working group involves a mix of participants, including assembly operators (2), middle management (1), process engineers (1), planning and logistics (1), production management (1), and management (1). Two external specialists guide the working group: one assembly engineer and one ergonomist. The specialists guide the company through the process and give their expert input. 2. Analysis (Step 2) The second step involves the analysis of the assembly process by setting up an assembly process scheme (MAS); which is drawn on paper during working group sessions. It visualizes the sequence of the various process steps that are required to assemble a certain product. Process steps that can occur in parallel are visualized in parallel with the main process flow (Fig. 9.3). The scheme also indicates where in the process these steps should end. Estimates of the time required for each process step are indicated, based on available data or estimates by the management and employees. Based on this scheme, the current layout, with its various work stations, is drawn. Discussions are carried out with the help of the work stations in the scheme. Questions for discussion include: What are the activities? and How is the transport managed between work stations? Finally, the division of the work among people is described in terms of whether individual workers make the whole product or only a part of it.

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Placement and alignment Mount Assemble upperframe frame on final upperframe on lowerframe 'assy' place

Mount unit A on frame

Mount unit BC on frame

Integration control cabinet into final product

119

Final test

Packaging final product

Assemble mech. unit A

Assemble lowerframe Preassemble mech. unit B

Mount Interelectr. unit mediate C on mech. test unit BC unit B

Preassemble mech. unit C

Assemble Intermediate electr. wiring test electr.

Mount electr. plate into cabinet incl. wiring

Test control cabinet

Preassemble electr. cabinet

FIGURE 9.3 Example of an assembly process scheme (MAS) of another case. (© TNO Industrial Technology.)

3. Problem definition (Step 3) In this step, the working group makes an inventory of the bottlenecks with regard to the material flow and ergonomics. Bottlenecks could be found regarding factory layout, the delivery of components, the availability of tools and equipment, the time needed to walk and search for tools and components, as well as the physical loads experienced in assembly or transport. In observations at the workplace and interviews with assembly workers, additional data are gathered. The assembly work and manual transport of materials are recorded by video. On the basis of these recordings the bottlenecks and potential improvements are discussed in the working group. 4. Improvement possibilities (Step 4) Based on the information from Step 3 and from the demands in terms of production volume and product variability, several concepts of the factory layout and the kind and number of work stations are formulated and discussed. The tasks of the workers and the characteristics of the work stations are defined for various options. From these options, the most productive and healthful assembly concept is selected.

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5. Test (Step 5) In the fifth step some test work stations are made to simulate the work. The available tools and equipment are used as much as possible. The workplace is designed in cooperation with the workers and management, evaluated, and then adapted. The focus is on the location of components and tools, the requirements of space, and the proper heights for picking and placing materials. Based on this experience, the new layout is chosen. 6. Implementation (Step 6) The assembly line and work stations are actually built and implemented in the sixth step. In this improvement process, Steps 1 through 5 took 3 months, with two sessions of the working group per week. Step 6 took 6 months to complete, including the time lost to order and receive the new equipment.

9.7

UNIQUE POSSIBILITY

In this project the new line was built in the same hall as the old line. Both lines operated simultaneously, which offered the unique possibility of evaluating the effects of the improvement thoroughly. Subjects could work for 3 months on the old line and then in the new situation, and their productivity and health could be measured and compared.

9.8 THE EVALUATION After the six steps were completed, a thorough evaluation of effects was carried out. Six workers who were familiar with the traditional and the new concept participated in this experiment. Their general experience in assembly work ranged from 1.5 to 12.5 years. The average age of this subject group was 30.7 years (range, 21 to 41 years). In this test, the six subjects worked both in the traditional manner and according to the new concept for an entire working day, while various subjective and objective measures were recorded. The subjects were asked to perform their tasks as they usually do (including, for instance, task rotation under the new concept) and at their normal working pace. Under both sets of conditions productivity was measured in terms of the number of products per person per day. Furthermore, the order lead time was calculated, that is, the time the product is in the line. The required floor surface was measured, including the workbench, the walking space at the work station, and the material storage space at the work station. From video recordings made in both situations, the activities were divided into added-value (assembling, mounting) and non-addedvalue (walking, sorting, searching) activities, and the time of added-value activities was calculated as a percentage of the total working time. With respect to the physical load on the workers, the time of occurrence of hazardous body segment postures was estimated by observation, and the risk involved in lifting situations was calculated. Also, the workers’ discomfort and fatigue were recorded.

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The body segment posture estimation was based on video recordings; the lifting situations were studied using the NIOSH equation (Waters et al. 1994). From the video recordings, estimates were made regarding the positions and angles of body segments, using a special computer program (Noldus). Local perceived discomfort (LPD) was recorded using a seven-point scale (Grinten and Smitt 1992). Standardized questionnaires were used to address the various aspects of the physical work load, the mental work load, the worker’s satisfaction, and the health risks in both the traditional and the new situation. Paired t-tests or the Wilcoxon test (in case of ranked pairs) were used to determine the significance of differences (p < 0.05) between both situations.

9.9 •

•

•

•

RESULTS OF THE SIX STEPS

Step 1 In the first step, the different groups were indeed installed as described in the method. Also, the goal was agreed upon: reducing musculoskeletal loading and reducing throughput times. Step 2 In the assembly process scheme for the emergency lighting device all subsequent activities is shown in Fig. 9.3. In the scheme, all subsequent activities that are required to assemble one device are presented. The scheme helped indicate the type of added-value activities (assembly) and non-added-value activities (fetching and spreading out components) that were required. A positive effect of developing the assembly process scheme is that all participants became aware of the advantages and disadvantages of the current assembly system. Step 3 In the left column of Table 9.1 some bottlenecks in material flow and ergonomics are shown. Step 4 To solve the problems mentioned in Step 3, various production concepts were studied. For each concept the effects on productivity and health were estimated. From these studies, two concepts were chosen and further specified. These concepts are presented in Fig. 9.4.

TABLE 9.1 Difference between the Old and New Production Line Order lead time Time/person/product Products/person/day Required work space Satisfied with work Physical workload: posture Physical workload: lifting

Old 155 min 5.2 min 93.3 80.5 m2 17% acceptable unacceptable

New 72 min 3.6 min 134.7 45 m2 83% acceptable acceptable

% Change −46 −31 +44 −44 66

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A.

B.

C.

FIGURE 9.4 Different production concepts that could improve the flow: (A) three parallel work stations; (B) three work stations in series; (C) two work stations supplying the third work station.

The first concept shows three parallel, individual workplaces. At each workplace one worker assembles a whole product (concept A). The second concept is an assembly line of three workplaces in series, where workers assemble parts of the final product and the products are handed over (concept B). The working group evaluated these concepts according to various aspects such as flow of materials and logistics, balancing of activities, work content per individual, time to learn (for new employees), and the flexibility to cope with volume and product variances.

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•

123

The advantage of concept A could be that the worker makes a whole product. This is considered advantageous because of less monotony in the tasks and higher worker satisfaction. In addition, this concept enables adaptation of the number of operators to the volume demand. A disadvantage could be longer learning time. A logistic disadvantage of concept A is that the three workplaces need to be identical, which means that the equipment at the workplaces (tools, aids) and the supply of components should be organized in triplicate. The advantage of concept B could be that components are supplied at only one workplace. However, the work content is smaller and there is less flexibility: three assembly workers are required to keep the line running. Based on concepts A and B, a new concept was defined by the working group. In this final concept (C), the various advantages of concepts A and B were combined. Concept C is characterized by an assembly line with three work stations. At two parallel work stations, two operators perform nearly all of the assembly steps. The nearly complete products are supplied from both work stations to the third work station, where the products are finished and packed. The content of the work is balanced, such that the workers do not have to wait for others. Small buffers between the first two work stations and the final one are established to enable workers to work at an individually preferred pace. Instead of a conveyor belt, which may stress the workers, a roller conveyor was chosen to transport products from the first two work stations to the final one. This roller conveyor was constructed with a certain deviation from the horizontal so that products would glide from one workplace to the other. Within the new concept, it is agreed that workers will rotate across the three workplaces every 2 hours. Finally, it was decided that the stock of materials on the work floor should not exceed the amount required for one production day. Step 5 In assembly concept C the work stations were also designed. All components are placed within reach by positioning small boxes in a tilted position. Several boxes containing components had to be placed in each work station, and to reduce reaching distances the sizes of the boxes were kept small. To get smaller quantities of components, agreements with suppliers had to be changed. Also, the design of some supply boxes had to be modified to improve reach and supply. For instance, the boxes with TLs were redesigned so that they could be refilled from above while lamps could be easily picked out from the side. Under the new concept, the workers refilled the boxes themselves. Where the workers sit at the first two work stations, a fixture was placed on which the product could be rotated and tilted. Furthermore, the light was improved, the screwing tool was positioned within reach and weightlessly balanced, and new and easily adjustable chairs and tables were implemented. At most work stations the worker is seated, but the worker

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•

stands at the work station where the final assembly takes place. The product could be tilted at this work station also to facilitate the assembling activities. Finally, to further facilitate the assembly some modifications of the product itself were recommended and applied. Step 6 All proposed improvements were implemented where six people work on each of two assembly lines.

9.10

RESULTS OF THE EVALUATION

Table 9.1 shows the effects on productivity, throughput time, and physical work load. Throughput time was reduced from 2 hours and 35 minutes to 1 hour and 12 minutes. The time spent per person per product was diminished, and the number of products per person was almost doubled. All of this could be accomplished in less work space than before. The employees were more satisfied with their work in the new situation (Fig. 9.5), but the participatory ergonomics process could also cause this. Figure 9.6 shows the working postures in percentages of total working time. There were no large differences in scored working postures, except for raising arms. In the new situation we observed that 12% of the time more arms were elevated within 20 to 60°. The NIOSH equations for lifting boxes (92 N per box) in both the old and the new situations showed an improved and safer way of lifting in the new situation. In the traditional situation, the lifting conditions were unacceptable because of the low placement (vertical factor) of the pallets on the floor (0.3 m) and the reaching

FIGURE 9.5 The new working situation.

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125

Working postures % of total working time

100.0

* *

80.0 60.0 40.0

*

20.0 *

Tr un Tr k fle un xi o k fle n 0 Tr xio -2 0 un n 20 k f l N ec exi 60 on k f N ec lex >60 i on k 0 N flex ec io -20 n k 2 f 0N lex ec 40 i k on fle 40 N xio -60 ec n 6 k fle 0-8 Ar xi on 0 m r >8 a Ar m ised 0 ra is 0Ar ed 20 m 2 ra 0W ise 60 ris d t d >6 ev 0 i N eu atio n tra lw N rist o ro Ye t/la t s ro t/l at

0.0

traditional new

FIGURE 9.6 Categorized working postures in the traditional situation and in the new situation (* = significant difference, p < 0.05).

(horizontal factor) required before placing. In the new situation the boxes were placed on a pallet at adjustable height (0.7 to 0.8 m) on a lifting table, so the workers did not have to reach as far. No differences were found for locally perceived discomfort in different body areas. Workers did experience less overall fatigue in the new situation, compared to the traditional situation (p = .038) (Fig. 9.7). There were no differences in experienced Experienced fatigue 7 6

traditional new

Score

5 4 3 2 1 0 1

2

3

4

5

6

Subjects

FIGURE 9.7 Experienced fatigue in the traditional situation and in the new situation, scored on a seven-point scale (1 = [almost] no fatigue; 7 = very much fatigue).

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workload and mental load. Five of the six subjects felt more satisfied with the new working concept. They considered their increased productivity, the improved work station design, and the reduction of lifting tasks to be the reasons.

9.11 DISCUSSION In this project, a traditional assembly concept in which workers make batches of products from start to finish was replaced by a concept in which workers make only one product at a time. This change, which also involved ergonomic workplace modifications, resulted in some clear effects. The beneficial effects on production measures are beyond dispute. There appeared to be no need for the company to invest in building a new factory hall, which was the original plan. It appeared to be possible to produce about twice as much in the same factory area when applying the new assembly concept. In addition, we observed a significant decrease in order lead time (46%). This gain in productivity is partly based on an increase in the percentage of time that is spent on added-value (assembly) activities. This significant shift toward more added-value assembly work did not lead to a clear increase in the physical or mental loads on the workers. In our objective and subjective measures, we observed no difference in load (local perceived discomfort, experienced work load, experienced mental load, the occurrence of stressful postures in most body segments) and a decreased load in the new situation (less lifting and a lower level of overall fatigue at the end of the day). One exception concerns the arm posture: Slightly more frequent moderate arm elevation is observed in the new situation. The increased arm elevations can be explained by the fact that part of the time the workers are seated, which requires more arm elevation when reaching for components from shelves. Modifying the way that the components are delivered now eliminates this disadvantage. Winkel et al. (2002) address the current general tendency in manufacturing toward work intensification (because of lean production, time-based management, or business process reengineering) and the elevated medically certified sick leave rates that might be associated with these developments (Vahtera et al. 1997). In our project the work also became more intense, as more time was spent on assembly. This leads to more products per worker per unit of time within the new concept. However, our results did not point toward elevated health risk, and some caution is recommended here. In this study we addressed the hazardous postures, hazardous lifting situations, and subjective experiences of people. We did not really address the important aspect of variation of actions over time. Monotonous work (low variation) in the production industry has been associated with increased health problems in the upper extremities and elevated sick leave rates in various studies (Johansson and Nonås 1994; Ólafsdóttir and Rafnsson 1998; Parenmark et al. 1993). With regard to task variation, we make the following observations from our own project. First, in the traditional situation the periods of assembly work (74% of the total working time) are alternated with periods of walking, carrying, lifting, and searching for components. One could argue that this alternation is favorable, although the proportion of the non-added-value activities is rather high and some of the activities

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(the lifting action) themselves might be hazardous. In the new situation, we also have the workers alternate assembly work with other work by requiring them to stand up and fetch components at rather fixed intervals of time. Some variation is thereby guaranteed, although the overall duration of other activities is downsized (to 8% of the total working time). Second, additional variation is introduced within the periods of assembly. In the traditional batchwise production, the same action is performed on 60 different products prior to proceeding with a new assembly action. By making one product at a time under the new concept, the variation in assembly activities is increased. As the types of these activities are rather diverse, we consider this to be a favorable feature. Workers themselves also considered this change to be a positive development, although some caution is needed here. Workers could also be positive because of their involvement in the change process. Finally, alternating sitting and standing is introduced in the new situation, whereas standing was the most observed way to assemble in the former situation. Taking all of the foregoing information into consideration, we see no clear adverse effects of the new situation due to the changes in activity variation over time. In conclusion, it appears to be possible to increase production without increasing — rather decreasing — the loads on the workers. This is in line with our experiences rather projects (Tuinzaad et al. 2000). To obtain this result, it is a prerequisite to reconsider the concept of assembly rather fundamentally and to think about new concepts of production in discussions with a team of experts (in ergonomics and assembly engineering) and company representatives (including workers).

9.12 CONCLUSIONS In this project, discomfort measurements are used to optimize the work station. Reducing discomfort in itself is important, but knowing that data on discomfort can prevent musculoskeletal injuries in the future strengthens its importance. The discomfort was not at a high level in the old situation and didn’t increase in the new situation, even with higher productivity. The comfort increased. This was not measured directly, but factors related to comfort, such as satisfied with work, were improved.

ACKNOWLEDGMENT The authors want to thank Faber Electronics BV for the nice collaboration.

REFERENCES Eijnatten, F.M. van, ed. (2002) Intelligent Manufacturing through Participation: A Participative Simulation Environment for Integral Manufacturing Enterprise Renewal, Hoofddorp: The PSIM Consortium/TNO Arbeid. Grinten, M.P. van der and Smitt, P. (1992) “Development of a practical method for measuring body part discomfort.” In S. Kumar, ed., Advances in Industrial Ergonomics and Safety IV, London: Taylor & Francis, 311–318.

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Johansson, J.Å. and Nonås, K. (1994) “Psychosocial and physical working conditions and associated musculoskeletal symptoms among operators in five plants using arc welding in robot stations.” International Journal of Human Factors in Manufacturing, 4(2): 191–204. Looze, M.P. de, Urlings, I.J.M., Vink, P., Rhijn, G. van, Miedema, M., Bronkhorst, R.E. and Grinten, M.P. van der (2001) “Toward successful physical stress reducing products. An evaluation of seven cases.” Applied Ergonomics, 32: 525–534. Matthiasen, S.E., Wells, R.P., Winkel, J., Forsman M. and Medbo L. (2002) “Tools for integrated engineering and ergonomic assessment of time aspects in international production.” In Humans in a Complex Environment, Proceedings 34th Annual Congress of NES, Linköping: Linköping University, 579–584. Ólafsdóttir, H. and Rafnsson, V (1998) “Increase in musculoskeletal symptoms of upper limbs among women after introduction of the flow-line in fish-fillet plants.” International Journal of Industrial Ergonomics, 21: 69–77. Parenmark, G., Malmkvist, A.K. and Örtengren, R. (1993) “Ergonomic moves in an engineering industry: Effects on sick leave frequency, labor turnover and productivity.” International Journal of Industrial Ergonomics, 11: 291–300. Rhijn, J.W. van, Looze, M.P. de, Groenesteijn, L., Groot, M.D. de, Vink, P., Tuinzaad, G.H. (2002) “Efficient flow and human centred assembly. The success of an interactive approach.” In Humans in a Complex Environment. Proceedings 34th Congress of NES, Linköping: Linköping University, 805–810. Rhijn, J.W. van, and G.H. Tuinzaad (1999) “Design of effecient assembly flow and human centered workplaces in Dutch assembly companies.” In Proceedings of the International Conference on TQM and Human Factors, Linköping. Sauter, S.L. and Swanson, N.G. (1991) Increased Rest Breaks Yield Increased Productivity in Repetitive VDT Work (revision per NIOSH reviewer’s comments). Presented at the annual meeting of the Human Factors Society. Tuinzaad, G.H., Rhijn, J.W. van, Deursen, J. van and Koningsveld, E.A.P. (2000) Efficient Flow and Human Centred Assembly: The Success of an Interactive Approach, Eindhoven/Hoofddorp: TNO Industrial Technology/TNO Work and Employment. Vahtera, J., Kivimaki, M. and Pentii, J. (1997) “Effect of organisational downsizing on health of employees.” The Lancet, 350: 1124–1128. Waters, T.R., Putz-Anderson, V., Garg, A. and Fine, L.J. (1993) “Revised NIOSH-equation for the design and evaluation of manual lifting tasks.” Ergonomics, 36: 749–776. Winkel, J., Forsman, M., Kazmierczak, K., Kjellberg, A., Mathiassen, S.E., Neumann, P.W. and Wells, R.P. (2002) “Ergonomic intervention for occupational musculoskeletal health in manufacturing industry — trends, tools and processes.” In Humans in a Complex Environment, Proceedings 34th Congress of NES, Linköping: Linköping University, 833–835. Yamada, S. (2002) “Challenges in dealing with human factors issues in manufacturing activities.” In H. Arisawa et al., ed., ER 2001 workshops–HUMACS, DASWIS, ECOMO, and DAMA, Yokohama. Berlin: Springer-Verlag, 10–29.

and 10 Productivity Discomfort in Assembly Work: The Effects of an Ergonomic Workplace Adjustment at Philips DAP M.P. de Looze, J.W. van Rhijn, N. Schoenmaker, M.P. van der Grinten, and J. van Deursen CONTENTS 10.1 10.2 10.3 10.4 10.5

Discomfort and Productivity......................................................................129 Discomfort in Assembly ............................................................................130 Market Demands Productivity Increase.....................................................130 The Philips Case ........................................................................................131 The Test Method ........................................................................................131 10.5.1 Subjects and Task ........................................................................131 10.5.2 Productivity ..................................................................................132 10.5.3 Discomfort ...................................................................................133 10.6 The Test Effect ...........................................................................................134 10.7 Discussion ..................................................................................................134 10.8 Conclusions ................................................................................................135 Acknowledgment ...................................................................................................135 References..............................................................................................................135

10.1

DISCOMFORT AND PRODUCTIVITY

As mentioned in Chapter 9, two major issues play a role in manual assembly operations: reducing discomfort as a precursor to health problems and increasing productivity. In this project the engineering department and the workforce adapted the production lines several times. Several tools such as simulation software were used, and at first sight the work stations looked very good at Philips DAP, where the project was taking place (Fig. 10.1). Nevertheless, experienced ergonomists who investigated the production line assumed that the work stations could be even further improved. This chapter describes the effect of this improvement on productivity and discomfort. 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

129

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FIGURE 10.1 A typical production line work station at Philips DAP.

10.2

DISCOMFORT IN ASSEMBLY

Musculoskeletal discomfort and pain in the neck and shoulders are serious problems in many occupations, often leading to sick leave or even disability. The etiology of these neck and shoulder disorders is multifactorial in nature (Johansson and Rubenowitz 1994). Both physical and psychosocial factors are associated with neck and shoulder disorders (Frederiksson et al. 2001). Among these factors are repetitive work, static and awkward postures, monotonous work, high work pressure, poor social support, and few opportunities to influence decisions. In assembly work, many of these risk factors are present. Specifically, frequent elevation of the arms, static neck flexion, and repetitive work are very common in assembly industries. Some assembly lines are also characterized by low personal control, high time pressure, and little variation. Therefore, it is not surprising that assembly work is mentioned as one of the tasks particularly associated with musculoskeletal discomfort and pain in the neck and shoulders (Hagberg and Wegman 1987). To keep the workforce optimally motivated, assembly companies should address these risk factors and minimize employees’ exposure to these risks. At the same time, however, these companies must meet other challenges, such as increasing the productivity and flexibility of their production lines.

10.3

MARKET DEMANDS PRODUCTIVITY INCREASE

In today’s worldwide competition, assembly industries are under a lot of pressure (Eijnatten 2002). To survive, companies are forced to increase the numbers of products, decrease delivery times, and minimize the costs. Where products are

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manually assembled, the pressure on the company is likely to reflect the pressure on the individual operator. In this context, an efficient assembly process is definitely needed. Currently, we see several tendencies toward more efficient production in the assembly process. There is a tendency toward more flow production, where products flow piece-by-piece from one station to the next. This concept is often believed to be more efficient compared to other concepts such as batchwise assembly or total assembly at one station (Rhijn et al., submitted: Looze et al. 2003). Another tendency is toward lean manufacturing (Docherty et al. 2002), which refers to a process in which the numbers of unnecessary steps, waste, and error are kept to a minimum. Lean manufacturing may very well improve efficiency, although others stress its detrimental effects on the operators resulting from an intensification of the work (Lansbergis et al. 1999; Vahtera et al. 1997). In addition to these conceptual considerations, there is a question as to the potential effect of ergonomic workplace adjustments on productivity at the work station level. In principle, an ergonomically well-designed work station would reduce physical discomfort, but it might also increase the workers’ productivity because in an optimally designed workplace, one might be able to work at a faster pace. However, this higher work rate might have the effect of increasing discomfort, which could neutralize any favorable effects. In the following case, we studied the effects of an ergonomic workplace adjustment in a typical assembly task, both on the productivity rate and on the level of discomfort of workers.

10.4 THE PHILIPS CASE Philips DAP is a division of the Philips Company (the Netherlands) that produces electric razors in very large volumes. In this company, an experiment was performed to study the effect of workplace adjustment on the productivity and the discomfort of the workers. In many work stations at Philips DAP, just as in many other companies, the location of supply containers, from which components have to be picked, is far from optimal. This is mostly due to the large numbers of different components that need to be at hand simultaneously. This leads to frequent, extended reaching and much arm elevation. Consequently, risks for shoulder discomfort and pain could increase. We decided for the experiment, therefore, that the workplace adjustment under investigation would be the lowering of the picking heights to comfortable levels.

10.5 THE TEST METHOD 10.5.1

SUBJECTS

AND

TASK

Fourteen female assembly workers, all working at Philips DAP, participated in the experiment. At the time of the experiment they had no health complaints. They had a work history at this company division ranging from 1 month to 11 years and were all able to work at the current standard work pace.

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TABLE 10.1 Actions per Cycle and the Division of Actions into Three Action Groups: Picking, Assembling, and Placing Action Picking two lockup plates from two supply bins Positioning these plates onto the product template Picking the first set of razor blades from two supply trays Pressing the first set of razor blades onto the lockup plate Picking the second set of razor blades from two supply trays Pressing the second set of razor blades onto the lockup plate Placing two razor heads in a product carrier

Action group picking assembling picking assembling picking assembling placing

We studied these workers when performing the task of assembling the heads of razors. The actions consisted of picking the components from small supply containers, assembling the razor heads, and placing the products onto a product carrier. The actions in one cycle are specified in Table 10.1. All actions were simultaneously performed by the left and the right hands resulting in two products per cycle. The duration of one cycle (of two products) was roughly 10 to 15 seconds, depending on the overall work pace. During the performance of the task, each subject was sitting on a chair that was adjustable in height and depth (distance from the front of the seat to the back rest). A height-adjustable footrest was also used. We tested the subject under two conditions. Condition high reflected the current situation, where the supply bins and trays and the product carrier were located at positions requiring considerably high upper-arm elevations. In condition low, these positions were significantly lowered (Fig. 10.2). All 14 subjects performed the task in both the high and the low condition. These performances took place on two consecutive working days, at the same time of day. The sequence of exposure to the low and high conditions was systematically varied across subjects.

10.5.2

PRODUCTIVITY

During the performance of the tasks a psychophysical protocol was applied in order to determine the maximum acceptable work pace (MAWP) in each situation. The MAWP is the work pace considered by workers to be the highest pace that is still acceptable for an 8-hour working day. At the start of this 50-minute protocol, the subjects were asked to begin working at a work pace that they considered productive and comfortable. Over the next 30 minutes, changes in the work pace took place every 2 to 3 minutes (after the production of 1 or 2 sets of 24 products). The first change involved a decrease in pace for half of the subjects and an increase for the other half. The next instructions regarding

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B

C C

133

C

A

B A

C

B

C BB A

AA

A

B BB

B

A

FIGURE 10.2. The high (upper and lower left) and low (upper and lower right) workplace conditions. In the low workplace condition the storage containers for the plates A and blades B are placed lower and closer to the subject, and the product carrier C is also lowered.

pace were designed to find out whether even lower (for the first group subjects) and even higher paces (for the second group) could be applied without becoming “unrealistic.” The criterion for the remaining work pace changes was the feeling of the subjects about the acceptability of the work pace. Thirty minutes appeared to be sufficient to find the MAWP in both conditions. No further changes were therefore applied after 30 minutes. Instead, the workers continued at the same pace for another 20 minutes.

10.5.3

DISCOMFORT

Every 5 minutes during the 50-minute protocol, the local musculoskeletal discomfort in various body regions was measured (Grinten and Smitt 1992). This approach applied a 10-point rating scale, where 0 = no discomfort and 10 = extreme discomfort.

TABLE 10.2 MAWP Expressed in Number of Products per Minute and as the Average across Subjects’ Localized Musculoskeletal Discomfort in the Neck and Shoulders as Measured at the End of the Test (after 50 Minutes) Condition Workplace high Workplace low

Average MAWP (range) 9.4 (6.7–13.0) 10.4 (7.2–14.6)

Average discomfort (sd) 1.1 (1.0) 0.4 (0.6)

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When a subject reported a discomfort level of 3 (moderate discomfort), the experimenter intervened in the test protocol by reducing the work pace.

10.6 THE TEST EFFECT Table 10.2 presents the maximum acceptable work pace and the level of discomfort averaged across subjects. We observed a significant effect of workplace condition. In the low workplace condition, the maximum acceptable work pace was significantly higher than in the high workplace condition. The difference between the high and the low condition was 1.0 product per minute. This implies a difference in work pace of 10.6%. Furthermore, it appears that the difference between the lowest work pace observation and the highest is defined by a multiplication factor up to 2.0. Further analysis showed that the MAWP had no relation to the level of experience (number of working years at the same factory). Despite the relatively low measured discomfort levels in general, we were also able to find significance for the effect of workplace condition on discomfort. Musculoskeletal discomfort in the neck and shoulders was significantly lower in the low workplace condition compared to the high workplace condition.

10.7 DISCUSSION Repetitive arm elevation is a well-known risk factor for the development of musculoskeletal discomfort and pain in the neck and shoulder region. Therefore, work stations where the number or degree of arm elevations is reduced seem favorable from the perspective of health. The lowered picking heights might also lead to a higher work pace, which might be advantageous from a productivity perspective. However, if the higher work pace would lead to increased levels of fatigue, the benefits of the lowered picking levels on the worker would still be under debate. In the present study, we determined the effects of a lowered picking height on both work pace and discomfort. The lowering of the picking height had a clear effect on the degree of arm elevation. In particular, the upper arm elevation during the activity of picking components (three times per cycle) was reduced from about 40° to about 10° (angle of the upper arm with respect to the vertical). The ergonomic adjustment led to a 10% higher work pace under low workplace conditions, and the local discomfort as perceived by the subjects was no higher. Instead, we even observed significantly lower levels of discomfort in the neck and shoulder region under low workplace conditions. The most important conclusion of the study is that by ergonomic workplace adjustment it is possible to create a win–win situation in terms of the simultaneous benefits for the company and the worker. Within the companies, the positive effect on productivity might help to convince production managers and cost engineers of the importance of ergonomic workplace adjustment. Such adjustments also constitute a risk from the human factors point of view. It appears that ergonomic workplace adjustment may well increase the work pace, in which case the work clearly becomes more repetitive and possibly more monotonous. In our case, this did not lead to more discomfort. However, it is not yet clear

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for all other cases that the beneficial effect of the ergonomic adjustment on discomfort would be larger than the potential negative effect of faster and more repetitive work. Moreover, for the specific adjustment of lowering picking heights, it is still important to evaluate whether the positive finding of less discomfort at higher productivity would also last over longer times (working days and weeks). To retain the positive effect on production and the worker over a longer term, it is important for the workers to take regular breaks and to rotate across tasks. Another strong recommendation would be to make a proper evaluation of the discomfort levels of workers during the working day, especially in all cases where ergonomic interventions would lead to a higher work pace.

10.8 CONCLUSIONS In high-volume manual assembly operations there is a clear link between work station design and worker discomfort. In the case discussed here, optimization of the work station layout reduced discomfort and increased productivity, which is of benefit to both the employees and the company.

ACKNOWLEDGMENT The authors want to thank Philips DAP for their wonderful support.

REFERENCES Docherty, P., Forslin, J. and Shani, A.B. (2002) Creating Sustainable Work Systems — Emerging Perspectives and Practice, London: Routledge. Eijnatten, F.M. van, ed. (2002) Intelligent Manufacturing through Participation: A Participative Simulation Environment for Integral Manufacturing Enterprise Renewal, Hoofddorp: The PSIM Consortium/TNO Arbeid. Frederiksson, K., Bildt, C., Hägg, C. and Kilbom, Å. (2001) “The impact on musculoskeletal disorders of changing physical and psychosocial work environment conditions in the automobile industry.” International Journal of Industrial Ergonomics, 28: 31–45. Grinten, M.P. van der and Smitt, P. (1992) “Development of a practical method for measuring body part discomfort.” In S. Kumar, ed., Advances in Industrial Ergonomics and Safety IV, London: Taylor & Francis, 311–318. Hagberg, M. and Wegman, D.H. (1987) “Prevalence rates and odds ratios of shoulder and neck diseases in different occupational groups.” British Journal of Industrial Medicine, 44: 602–610. Johansson, J.Å. and Nonås, K. (1994) “Psychosocial and physical working conditions and associated musculoskeletal symptoms among operators in five plants using arc welding in robot stations.” International Journal of Human Factors in Manufacturing, 4(2): 191–204. Lansbergis, P.A., Schnall, P. and Cahill, J. (1999) “The impact of lean production and related new systems of work organisation on worker health.” Journal of Occupational Health Psychology, 42: 108–130.

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Looze, M.P. de, Rhijn, J.W. van and Tuinzaad, B. (2003) “A participatory and integrative approach to improve productivity and ergonomics in assembly.” Production Planning and Control, 14: 174–181. Rhijn, J.W. van, Looze, M.P. de, Groenestein, L., Groot, M. de, Tuinzaad, G.H. and Vink, P. (2003) “The design of a new assembly concept for improved ergonomics and design.” International Journal of Production Research (submitted). Vahtera, J. (1997) “Effect of organizational downsizing on health of employees.” The Lancet, 350: 1124–1128.

in Furniture 11 Comfort at Home T. Teraoka, R. Mitsuya, and K. Noro CONTENTS 11.1 Introduction ................................................................................................137 11.2 Participatory Design...................................................................................138 11.3 Developing Four Sizes ...............................................................................139 11.4 The Experiment..........................................................................................140 11.5 Results of the Lab Experiment ..................................................................141 11.6 Results of the Trade Fair ...........................................................................142 11.7 Conclusions ................................................................................................144 Acknowledgments..................................................................................................144 References..............................................................................................................145

11.1 INTRODUCTION In designing a piece of furniture for use at home, comfort also plays a role. One of the factors to be considered in the design is the human body size. The comfort is affected by the relationship between the product size and the user’s body size. This relationship is often studied in the field of ergonomics (Croney 1981). Working chairs have been the object of study for many years (Chapters 2 and 3). An important aspect in this regard is the adjustability of the chair to the body size and posture needed for performing the task. However, dining chairs are mostly not adaptable, probably because they are made of wood. With wood, it is very difficult to make chairs adjustable as in office chairs. A solution for adapting to the difference in body size is to design the dining chairs in several sizes, as in shoes and clothing. Therefore, the Noro Laboratory of Waseda University and the Japan Freelance Interior Coordinator Association (JAFICA) developed four sizes (XS, S, M, and L) of chairs for the same model. The chairs were exhibited at IFFT2000 (International Furniture Fair, Tokyo 2000, November 21–24, 2000). Noro Lab led the development of the different sizes and the experiment to test the prototypes of the chairs. The eleven prototypes were manufactured by three wooden furniture manufacturers (Karimoku, Kosuga, and Interior Center) (Fig. 11.1). Two chairs were made in four sizes and one in three sizes. 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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XS

S

M

L

Manufacturer Karimoku Model CT1700UP

Manufacturer Kosuga Model 1492-DCH

Manufacturer Interior Center Model Runtom

FIGURE 11.1 The eleven chairs used in this study.

11.2 PARTICIPATORY DESIGN It is possible to base a chair design on anthropometrical data and computer models only. However, as stated earlier, human behavior and the comfort experience are hard to predict. Therefore, ordinary people participated in this academic study. Another reason why they were included is that there could a difference in experience between what academics think is important and what the common understanding is. The only way to gather useful ideas and information is to involve the real end users (Noro 1999; Vink 2002). Especially in the field of ergonomics, where the object is to support the user, the participation of the public is essential. The participatory approach reported in this chapter is an attempt to build an information loop between the manufacturers, who are suppliers of the product, and the users who are the consumers. In the Noro Laboratory there is a seating clinic where advice on how to choose and use chairs is given to the clients. The clinic is the place where researchers provide information about chairs to users, but at the same time researchers have opportunities to get information from the users. In this example, the seating clinic is a bridge between the public users and the manufacturers (Fig. 11.2). In the same way, the exhibition at IFFT2000 and the study on the size of chairs could be seen as similar bridges (Fig. 11.3).

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FIGURE 11.2 The gap bridged by the seating clinic.

FIGURE 11.3 The exhibition booth at IFFT2000.

11.3 DEVELOPING FOUR SIZES Based on the demands from users for a better fit, four sizes of prototype chairs were made. Up to that point, manufacturers had been used to manufacturing one size, but for the exhibition at the IFFT2000 four sizes were developed. The mass media paid some attention to this topic. Just before the IFFT, a national newspaper reported the study on the size of dining chairs conducted by Noro Lab and JAFICA.

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XS

140

150

S

M

L

160 170 Body Height (cm)

180

190

FIGURE 11.4 Assumption of the relationship between chair size and body height.

TABLE 11.1 Seat Heights of the Exhibited Chairs, in Millimeters (mm) Model CT1700UP (Karimoku) 1492-DCH (Kosuga) Runtom (Interior Center)

XS 370 390

S 395 415 410

M 420 440 435

L 445 465 457

The sizes of the chairs were chosen to fit the most people, from small to large and from young people (except children) to seniors. The current standard chair was defined as size M (medium), and three other sizes — XS (extra-small), S (small), and L (large) — were added. The differences in size were chosen to allow for height differences of as little as 0.1 m. The largest difference in sizes was 0.4 m (Fig. 11.4). The choice of the correct seat height was made on the basis of the lower-leg length. Assuming that the average lower-leg length is approximately one fourth of the body height (Molenbroek and Dirken 1987), the chair height difference of 0.1 m will correspond to approximately 0.025 m of lower-leg length. Therefore, the seat height of chair size S is 0.025 m lower than that of size M (Table 11.1). To keep the proper design of the other sizes equivalent to size M, all four sizes were made in the same proportion. It was expected that more comfort would be experienced in the size that best fits the subject. This was tested in an experiment.

11.4 THE EXPERIMENT Two experiments were performed: a lab test with 14 subjects and a test at the IFFT fair with 591 subjects. In the lab test 14 healthy subjects (7 male, 7 female) participated. Their ages were from 20 to 66 and their height ranged from 1.468 m to 1.803 m (Table 11.2). After their body sizes were measured, the subjects were asked to sit on each of the 11 chairs. As they sat, photographs of the postures were taken and the body pressure distribution was measured on the seat and the backrest for all 11 chairs. Afterward, the subjects gave their preference. For measuring the pressure distribution, the Force Sensitive Applications by Verg Inc. (Canada) was used. The experiment at the IFFT consisted of questioning the visitors who tested the chairs. Interest in the exhibition booth was high, and a large number of people sat on

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TABLE 11.2 Height, Age, and Sex of the Subjects Subject A B C D E F G H I J K L M N

Height (cm) 146.8 149.6 150.3 150.5 157.1 164.4 166.7 167.6 169.0 171.3 171.4 171.7 173.9 180.3

Age 66 22 54 43 45 23 24 20 62 26 20 21 27 24

Sex Female Female Female Female Female Female Male Male Male Male Female Male Male Male

the exhibited chairs. The visitors who tested the chairs seriously were asked to complete a short questionnaire, and 591 people completed it in 4 days. The main questions asked their age, sex, body height, and the comfort score on the 11 chairs. Properly answered questions from 434 people were collected and used in the results.

11.5

RESULTS OF THE LAB EXPERIMENT

The lab experiment results included a subjective evaluation. In Fig. 11.5 the result of the subjective preference is shown for the four sizes of chairs. The horizontal axis is the subject’s height and the vertical axis shows the size of the chair to which the subject gave the highest comfort value. However, each chair was valued at grade 5 (good) independently (Fig. 11.6), which resulted in more chairs with highest values. In that case, we used the average size of the chair. For example, when a subject gave the highest value to sizes S and M, we plotted the middle point between S and M. Nobody gave the highest value to size XS. Regarding seating posture and pressure distribution, Fig. 11.7 shows the seating posture and the pressure distribution of subject D (height: 1.505 m) sitting on model 1492-DCH. In the smallest chair, the pressure is high and localized under the buttocks. The thighs support relatively little weight. With sizes M and L, the seat height is too high for the body size, so the soles of the feet do not touch the floor. This causes much pressure under the front of the upper legs. Subjects A, B, and D do not touch the floor when sitting in size M of all three models, and the feet of subject E (height: 1.468 m) do not touch the floor even in size S of all the three models. Contact between the soles of the feet and the floor is preferred in order to have a good fit with the body, thus preventing reduction in blood flow or nerve pressure in the back of the upper leg that may cause swelling and numbness.

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FIGURE 11.5 The fit of fourteen subjects for the four sizes of chairs (XS, S, M, and L). The height of the subject is shown on the x-axis. Every dot is the highest comfort score given by the subject. The line is the regression line.

FIGURE 11.6 The question used to evaluate the chair comfort.

11.6

RESULTS OF THE TRADE FAIR

These results differ somewhat for the different chairs. The results for model CT1700UP give a good general idea and will be presented here. There were 192 people who answered the questions about this chair (Fig. 11.8). Figure 11.9 shows the percentage of people who preferred a specific size for a category of lengths. The lengths of the subjects were arranged in groups of 0.05 m, and each group was normalized to 100%. Most of the people with a body height shorter than 1.50 m selected chair size XS. Nobody preferred size M. Of the people taller than 1.50 m and shorter than 1.55 m, 61% selected size S. Among the people between 1.55 m and 1.60 m in height, the number that selected size S was equal to the number that selected size M (both 44%).

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S

M

L

Pressure Distribution

Seating Posture

XS

143

FIGURE 11.7 Seating posture and pressure distribution of subject D (height: 1.505 m) sitting on chair model 1492-DCH.

40 Male Female

Number of People

30

20

10

0 140 145 150 155 160 165 170 175 180 185 190 Body Height (cm)

FIGURE 11.8 Body heights of the 192 subjects who completed the questionnaire for chair model CT1700UP.

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S

70%

XS

60% 50% 40% 30% 20% 10% 0% 145

150

155

160 165 170 Body Height (cm)

175

180

185

FIGURE 11.9 Subjects who preferred each size of chair, grouped by height.

11.7 CONCLUSIONS As expected, shorter people tend to prefer smaller-sized chairs and taller people prefer the larger ones. Also, the feeling of comfort is highest in the chairs that fit better because the pressure is better distributed when the chair fits well. This conclusion is in alignment with the literature (Looze et al. 2003). At the same time, it is obvious that chair preference differed greatly among subjects. As an example, among subjects ranging in height from 1.55 to 1.60 m and from 1.60 to 1.65 m, there was a preference expressed for every size. The first reason for this is that the subjects had different reasons for their preferences. Second, the subjects were used to the size M chair (for example) that they used most often in daily life, and they felt a sense of incongruity with the size XS, S, and L chairs. Third, all four sizes are built with the same proportions, but some people just like a cute little chair. The challenge for the future is to find out whether long-term use would produce the same results and which of the three reasons just mentioned are really important. Also, studying use of the chair in its natural environment (including in relation to table height) could result in other figures.

ACKNOWLEDGMENTS Special thanks to JAFICA; chair manufacturers Karimoku, Kosuga, and Interior Center; and many users for supporting this study.

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REFERENCES Croney, J. (1981) Anthropometry for Designers, New York: Van Nostrand Reinhold Co. Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discomfort and the relationships with objective measures.” Ergonomics, 46: 985–998. Molenbroek, J.F.M. and en Dirken, J.M. (1987) “DINED-tabel.” In M.R. Creemers et al., eds., Polytechnisch Zakboekje, Arnhem: PBNA, J3/12–13. Noro, K. (1999) “Participatory ergonomics.” In W. Karwowski and W. S. Marras, eds., The Occupational Ergonomics Handbook, Boca Raton: CRC Press, 1421–1429. Vink, P. (2002) Comfort, Delft: Delft University of Technology (inaugural address).

and 12 Discomfort Dynamics in Office Chairs M.P. de Looze, P. Vink, and J.H. van Dieën CONTENTS 12.1 Chair Design Requires More Knowledge..................................................147 12.2 Discomfort and Office Chairs ....................................................................147 12.3 Dynamic Chairs..........................................................................................148 12.4 This Study ..................................................................................................148 12.5 Subjects and Chairs....................................................................................149 12.6 The Experimental Task ..............................................................................149 12.7 Measurements.............................................................................................150 12.8 Data Analysis .............................................................................................151 12.9 Results and Discussion ..............................................................................151 Acknowledgment ...................................................................................................153 References..............................................................................................................153

12.1

CHAIR DESIGN REQUIRES MORE KNOWLEDGE

Currently, the majority of the work force in the Netherlands is working in offices, as the service industry has grown and much work has been automated (Smulders et al. 2002). This means that many people spend much of their lifetime sitting on office chairs. Consequently, the market for office chairs is large; there are many chair manufacturers and many different office chairs. The question is: What is the optimal chair providing minimal discomfort and no health complaints in the long run? This question is not easy to answer. The scientific studies on discomfort and health effects of office chairs are rather limited. For instance, it is not known whether a dynamic chair is better with regard to discomfort and health than a static seat.

12.2

DISCOMFORT AND OFFICE CHAIRS

Various studies show that prolonged sitting in office chairs leads to elevated levels of physical discomfort in the low-back region (Looze et al. 2003). This increased discomfort has been assumed to increase the rates of low-back disorders among 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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office personnel. Indeed, back complaints are frequently mentioned among office workers (Smulders et al. 2002). Hales and Bernard (1996) demonstrated that prolonged sitting constitutes a potential risk factor for the development of low-back pain. On the other hand, recent reviews did not find the statistical evidence to support this statement (Hoogendoorn 2001). Anyway, it is obvious that chair designers should prevent discomfort in sitting as much as possible. There is much discussion as to whether physical discomfort in sitting can be attributed to the magnitude of the internal load. For many years, it was believed that sitting leads to higher stress compared to standing (Andersson et al. 1974). This has influenced manufacturers to design backrests that align with the natural spinal curve in the standing posture. More recent measurements on intervertebral disks, however, point to identical or even lesser stress on the spine while sitting (Wilke et al. 1999). Currently, there is still much debate on the optimal sitting posture. On the other hand, there is general support for the assumption that it is the continuous static character of the load, rather than the magnitude of the load, that leads to discomfort in sitting. According to Graf et al. (1995), a good chair would therefore be a chair that supports the body in a variety of desirable positions.

12.3 DYNAMIC CHAIRS A now fairly common characteristic of office chairs is that they have been designed to accommodate a substantial amount of movement. So-called dynamic chairs allow movement of the chair seat and back support, either in a fixed ratio or independently. Several authors have advocated this principle as a means of preventing sitting-related low-back pain (Kroemer 1994; Serber 1994; Suzuki et al. 1994). However, to our knowledge no scientific studies have been performed to support or refute this claim.

12.4 THIS STUDY The aim of the present study was to investigate the effects of dynamic office chairs on low-back parameters that might potentially affect low-back discomfort and health. We studied three types of office chairs that differed with respect to the dynamic mechanism. The parameters studied were the amount of trunk movement, the activity of the back muscles, the degree of spinal length change during sitting, as well as the perceived level of discomfort at the low-back level. The spinal length change was taken as an indicator for low-back load. It has previously been suggested that prolonged low compression acting on the discs during sitting hampers fluid flow into the disc and consequently affects disc nutrition adversely, which could cause back problems. In line with this hypothesis, spinal length change measurements were previously used to assess the effects of different chairs, for instance, demonstrating the advantage of back supports (Althoff et al. 1992; Eklund and Corlett 1987).

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FIGURE 12.1 Chairs that were used in the test. Chair (A) was used in both a dynamic mode (DA) and a fixed mode (FA); chair (B) was used in a dynamic mode (DB) only.

12.5

SUBJECTS AND CHAIRS

Ten healthy subjects, three females and seven males, participated in the experiment after signing informed consent. Their mean age was 21 (21 to 24) years, their mean height was 1.81 (1.71 to 1.90) meters, and their mean body mass was 75 (65 to 87) kilograms. All subjects were experienced users of word processing and computeraided design (CAD) software. Three types of chairs were used in the experiment (Fig. 12.1): chair DA, allowing independent sagittal plane rotation of backrest and seat; chair DB, allowing rotation of the seat in a fixed ratio to backrest rotation (1:2.7); and chair FA, which was chair DA in the mode wherein the backrest and seat pan were fixed (seat horizontal and the backrest at a 95° angle with respect to the seat). The chairs were adjusted for each subject according to a fixed protocol. A more detailed description of this experiment can be found in Dieën et al. (2000).

12.6

THE EXPERIMENTAL TASK

Each subject participated in three sessions (one with each of the three chair types) on separate days, starting at the same time of day. The chairs were used in random order. In each session, a standardized 3-hour task was performed. The task consisted of three activities: word processing, reading a book, and CAD. The word processing task consisted of reproducing a printed text. The CAD task involved reproducing a drawing provided on paper, mainly using the mouse as an input device. Word processing and CAD were performed in three blocks of 45 minutes, separated by 15 minutes of reading (Fig. 12.2). During the 3-hour session, the subject was not allowed to rise from the chair. Prior to the experimental task and the stature measurements, each subject performed at least two maximum isometric trunk extension efforts to obtain an estimate of maximum erector spinae muscle activation.

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0

60

120

180 reading

word processing

reading

drawing

reading

word processing

time (min)

FIGURE 12.2 Time schedule for each subject.

12.7 MEASUREMENTS Markers were attached to the subject at the level of the C7 spinous process; at the right hip, knee, and ankle joints; and over the axis of rotation of the seat to measure movement. Marker positions were recorded on video (sVHS), and the camera was positioned to provide a sagittal plane image (Fig. 12.3). Video frames were digitized and marker locations were determined semiautomatically using commercially available WINanalyze software. The change in length of the spine under the influence of a change in compressive loading was estimated with a stadiometer (Fig. 12.4) based on previously described equipment (Dieën et al. 1994; Eklund and Corlett 1984). In short, this instrument allows for reproducible (within 1 mm) measurements of stature by providing feedback to the subject as to the accurate reproduction of his or her posture from one measurement to another. Twenty measurements of stature were performed just prior to the experimental task, and twenty were performed immediately after the task. Perceived discomfort was measured by the local postural discomfort technique (Chapter 2).

FIGURE 12.3 Markers placed on the subject, and the experimental position of the subject.

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FIGURE 12.4 Spinal shrinkage measurement system (stadiometer).

12.8 DATA ANALYSIS Analysis of the marker data was based on the exposure variance analysis as proposed by Mathiassen and Winkel (1991). Only the C7 marker coordinates were used for further analysis because the other markers were found not to provide additional information on trunk kinematics. The last ten stature measurements taken before and the first ten after the task were averaged, and the differences between these were used to estimate spinal shrinkage. The remaining measurements were used to check the reproducibility of the measurements and will not be reported here. Two-way ANOVA for repeated measures was used to test for effects of task (word processing, CAD, and reading) and chair (FA, DA, DB) on kinematic variables. A nonparametric test (Friedman) was used to test for effects of chair type on shrinkage and discomfort.

12.9

RESULTS AND DISCUSSION

The largest effects with regard to movement and muscle activity were not found among chairs, but among tasks. More postural and muscle activity changes occurred

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% Spinal Length Change

0.6

*

0.5 0.4

* 0.3 0.2 0.1 0

dynamic A

dynamic B

fixed A

FIGURE 12.5 The change in spinal length caused by sitting in the three office chairs (* = significantly different from the static chair).

in reading compared to the word processing and CAD tasks. The differences in postural and muscular variations across tasks give support to the often-heard organizational recommendations toward more complete tasks or more task variation (Vink et al. 1998). We also found differences among the chairs, though to a minor extent. Although we did not find any significant difference in perceived discomfort, or in muscle activity or the number of movements from one chair to another, the spinal length data were different (Fig. 12.5). It was found that spinal length increased during the 3-hour period of sitting on both dynamic chairs, but the spinal length remained constant when sitting on the static chair. This result is an indication that the spine was less loaded on the dynamic chairs than on the static chair. Similar effects on spinal length change have been reported to occur when using a chair that imposes cyclic rotator movements on the spine (Deursen et al. 1999). The beneficial effect on stature change might lead us to the conclusion that dynamic chairs, such as the ones used in this study, should be advocated. However, it is our experience that in practice, many of the dynamic chairs are not used in the proper way. The use of dynamic chairs in their fixed mode is quite common. The introduction of dynamic chairs probably needs to be accompanied by careful instruction, or even training, of the future user. Another option in this respect might be offered by chairs promoting passive movement, as described by Deursen et al. (1999). Potential health effects of dynamic chairs or chairs providing passive motion need to be confirmed in field studies. The aim of the present study was to investigate the effects of dynamic office chairs on the low back, which might potentially affect low-back discomfort and health. Two dynamic office chairs were compared to one fixed chair. The results showed the advantage of the dynamic chairs: spinal-length measurements indicated

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a beneficial effect. However, a more evident effect was shown by the differences in tasks. This indicates that ergonomic measures in the office environment should be more focused on the design of functions than on the design of the chairs.

ACKNOWLEDGMENT The authors want to thank ASPA Kantoorinrichting BV, an office furniture company, for their support in this study.

REFERENCES Althoff, I., Brinckmann, P., Frobin, W., Sandover, J. and Burton, K. (1992) “An improved method of stature measurement for quantitative determination of spinal loading.” Spine, 17: 682–693. Andersson, G.B.J., Örtengren, R., Nachemson, A. and Elfström, G. (1974) “Lumbar disc pressure and myo-electric back muscle activity during sitting.” Scandinavian Journal of Rehabilitation Medicine, 6: 101–121. Deursen, D.L. van, Goossens, R.H.M., Evers, J.J.M., Helm, F.C.T. van der and Deursen, L.L.J.M. van (1999) “Length of the spine while sitting on a new concept for an office chair.” Applied Ergonomics, 31: 95–98. Dieën, J.H. van, Creemers, M., Draisma, I., Toussaint, H.M. and Kingma, I. (1994) “Repetitive lifting and spinal shrinkage: Effects of age and lifting technique.” Clinical Biomechanics, 9: 367–374. Dieën, J.H. van, Looze, M.P. de and Hermans, V. (2001) “The effects of dynamic office chairs on trunk kinematics, trunk extensor EMG and spinal shrinkage.” Ergonomics, 44: 739–750. Eklund, J.A.E. and Corlett, E.N. (1987) “Evaluation of spinal loads and chair design in seated work tasks.” Clinical Biomechanics, 2: 27–33. Eklund, J.A.E. and Corlett, N. (1984) “Shrinkage as a measure of the effect of load on the spine.” Spine, 9: 189–194. Graf, M., Guggenbuhl, U. and Krueger, H. (1995) “An assessment of seated activity and postures at five workplaces.” International Journal of Industrial Ergonomics, 15: 81–90. Hales, T.R. and Bernard, B.P. (1996) “Epidemiology of work-related musculoskeletal disorders.” Orthopedic Clinics of North America, 27: 679. Hoogendoorn, W.E. (2001) Work-Related Risk Factors for Low Back Pain. Amsterdam: Vrije Universiteit (Ph.D. thesis). Kroemer, K.H.E. (1994) “Sitting (or standing?) at the computer workplace.” In R. Lueder and K. Noro, eds., Hard Facts about Soft Machines, London: Taylor & Francis, 181–191. Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discomfort and the relationships with objective measures.” Ergonomics, 46: 985–998. Mathiassen, S.E. and Winkel, J. (1991) “Quantifying variation in physical load using exposure vs time data.” Ergonomics, 34: 1455–1468. Serber, H. (1994) “The study of lumbar motion in seating.” In R. Lueder and K. Noro, eds., Hard Facts about Soft Machines, London: Taylor & Francis: 423–431.

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Smulders, P.G.W., Houtman, I.L.D. and Klein Hesseling, D.J., eds. (2001) Trends in Work 2002, Alphen a/d Rijn: Kluwer (in Dutch). Suzuki, Y., Sugano, T. and Kato, T. (1994) “An ergonomic study of dynamic sitting.” In R. Lueder and K. Noro, eds., Hard Facts about Soft Machines, London: Taylor & Francis, 347–373. Vink, P., Koningsveld. E.A.P. and Dhondt, S., eds. (1998) Human Factors in Organizational Design and Management, IV, Amsterdam: Elsevier. Wilke, H.J., Neef, P., Caimi, M., Hoogland, T. and Claes, L.E. (1999) “New in vivo measurements of pressures in the intervertebral disc in daily life.” Spine, 24: 755–762.

Comfortable 13 Designing Passenger Seats R.E. Bronkhorst and F. Krause CONTENTS 13.1 13.2 13.3 13.4 13.5 13.6 13.7

Introduction ............................................................................................... 155 Method: Sitting Behavior...........................................................................156 Method: Benchmark Study ........................................................................156 Modifications..............................................................................................156 Method: Test of the Prototype Seat ...........................................................156 Results: Sitting Behavior ...........................................................................157 Results: Benchmark Study.........................................................................158 13.7.1 Ingress and Egress .......................................................................160 13.8 Modifications..............................................................................................162 13.9 Redesign Proposals Based on End-User Opinions....................................163 13.9.1 Angle of Seatback and Bottom Cushion .....................................163 13.9.2 Armrest Height.............................................................................164 13.9.3 Backrest .......................................................................................164 13.9.4 Headrest........................................................................................164 13.9.5 Back Shell ....................................................................................165 13.10 Results: Test of the Prototype Seat............................................................165 13.11 Conclusions ................................................................................................166 Acknowledgment ...................................................................................................167 References..............................................................................................................167

13.1 INTRODUCTION To attract more passengers, new seats were developed for new commuter trains scheduled to run in the United States. Several parties were involved in this study: Long Island Railroad (the commuter train company), Bombardier (the manufacturer of the train), and Multina (the seat manufacturer). TNO was asked to provide design input concerning the overall comfort experienced by passengers. This chapter describes the process that was used to develop a new seat.

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155

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13.2

METHOD: SITTING BEHAVIOR

After a search on the Web, among colleague institutes, and in the literature, it appeared that there was no knowledge available on how people sit in a commuter train and what their main activities were. Therefore, the project started with observing the behavior of passengers on the trajectory where the new train will ride. Measurements were taken to monitor the passengers’ activities, posture, size, and movements. From 1700 observations the 4 most frequent tasks were selected, as well as the essential anthropometrical characteristics.

13.3

METHOD: BENCHMARK STUDY

It was known by the commuter train company that passengers appreciate one particular seat. This existing seat, hereafter referred to as S1, was chosen to serve as a benchmark. A laboratory study was done to find out why this seat was appreciated. This S1 benchmark seat was tested along with the older-type seat (S2) that was used during the field observations. Eighteen subjects, selected according to the anthropometry found in the field test, participated in the test, representing the end users. They were asked to sit in specific ways that resembled four postures observed during the tasks in the field test. Specially designed questionnaires were used to ask test subjects about various parts of the seat. The following are examples of the detailed questions on the back seat cushion: • • • • •

How do you rate the general comfort of the back seat cushion? (5-point scale) How satisfied are you with the back seat angle? (3-point scale) Does the back seat give you enough support for your lower back? (3-point scale) Is the lumbar support in the right position? (3-point scale) Does the lumbar support have enough volume? (3-point scale)

Subjects were also asked to complete a local postural discomfort (LPD) questionnaire (Fig. 13.1; see also Chapter 2).

13.4 MODIFICATIONS Modifications were made to S1 based on this questionnaire information. In Phase 3 of the study, various modifications to S1 were tested by a group of new test subjects to confirm or adjust the design input. The manufacturer then built a prototype of the new seat, referred to as S3.

13.5

METHOD: TEST OF THE PROTOTYPE SEAT

In the next phase, the prototype S3 was tested against the S1 in the lab in a longduration, paired-comparison test to check the effect of the new seat on comfort. The lab testing consisted of various elements aimed at collecting data on three levels: passenger opinion; expert opinion; and objective data such as seat-pressure distribution quality.

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FIGURE 13.1 LPD map of the body showing the separate regions to be given a discomfort score on a 0–10 scale.

13.6

RESULTS: SITTING BEHAVIOR

To characterize the use of the seats and the passengers’ activities and movements, 1700 observations were taken. The ways passengers enter and leave the rows of seats and their actual tasks were studied. The postures in these tasks were recorded and described in terms of the angles of body segments. Because of the variety in anthropometrics among the population using the train, data on posture and size were collected during the field test. Results of the field test showed that about two thirds of the passengers sit in the straight position seen in the ergonomic manikins. Others use the seat in a different way, for example, with stretched legs, with folded legs, or for sleeping. For the new S3 seat it was considered important to facilitate all major postures that were observed (Table 13.1).

TABLE 13.1 Characteristics of Sitting Postures in a Commuter Train (Percentage of Total Time Observed) Sitting postures Leaning against backrest Leaning forward Slumped in seat Leaning toward to the right or the left Legs parallel, feet on floor Legs wide Legs stretched out Legs crossed Feet on heater Legs propped against seat in front or on other chairs

Men (%) 63 4 20 13 24 41 7 14 8 6

Women (%) 73 4 10 13 52 10 5 22 4 5

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TABLE 13.2 Activities Observed in a Commuter Train (Percentage of Total Time Observed) Activities Sleeping/napping Listening to music/talking/staring Reading a newspaper Reading a book or magazine Writing and typing

n 423 530 268 192 64

% 29 36 18 13 4

n = number of subjects observed doing the activity.

Sleeping or napping, reading (newspaper or books), and relaxing (listening to music, talking, or staring out the window) are the three most frequently observed activities. These activities divided the passenger population into almost equal thirds (Table 13.2). There were slightly more male than female commuters. The majority of the population measured average in both height and weight. Only 4% of the passengers chose to sit in the middle seat, 50% preferred the aisle, and 46% chose the window seat. The number of times an activity was observed and the percentage of times it was observed are listed in Table 13.2.

13.7

RESULTS: BENCHMARK STUDY

The lab tests were carried out at the Ergolab in the Netherlands. A test site was built as shown in Fig. 13.2.

FIGURE 13.2 The test setup in the Ergolab.

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TABLE 13.3 Five Levels of Seat Element Ratings % “(very) comfortable/good” >75 60–75 40–59 25–39 <25

Rating ++ + +/− − −−

A seat that is comfortable in the short term (often referred to as showroom comfort) may not necessarily be comfortable after a long period of sitting. Feelings of discomfort may arise only after a period of prolonged sitting, which requires a test of prolonged sitting duration. Discomfort is regularly avoided by changing one’s posture (Chapter 3). It is therefore necessary to have subjects maintain a specific posture in order to collect precise data on discomfort. As mentioned earlier, the lab tests consisted of various elements. All tests were done under controlled conditions. To facilitate discussion of the results with the designers and with the management of Long Island Railroad, Bombardier, and Multina, the seats were color-coded light green, green, white, red, and dark red, represented with plus and minus signs as shown in Table 13.3. Eighteen subjects were asked to sit for 1 hour on seat S1 or S2, during which time specific postures had to be maintained that resembled postures observed in the field test. Nine subjects started on S1 and nine on S2. After a short break the subjects were asked to change seats, at which time ingress and egress tests were performed and the sitting test was continued on the other seat. Results are shown in Tables 13.4 and 13.5. Neither the S1 (benchmark) nor the other seat (S2) had a comfortable seat cushion. The test subjects had comments on various aspects. The total score for the benchmark

TABLE 13.4 The Evaluation of Two Seats, S1 and S2, by End Users Seat cushion criterion Comfortable Height to floor Width Depth Angle backward Hardness of cushion Support for legs and buttocks Cushion cover Postural constraints of row in front

S1 +/− + ++ +/− + +/− +/− − −−

S2 −− + ++ +/− + +/− +/− + +/−

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TABLE 13.5 Backrest and Entire Seat Evaluation Results of the Two Seats Criterion

S1

S2

+/− ++ +/− +/− +/− +/− +/− −− −−

−− ++ + +/− +/− +/− +/− −− −−

+/−

−−

Backrest Comfortable Width Angle backwards Hardness cushion Lumbar support Lumbar height Lumbar swell Upper back support Head support Entire seat Comfortable

seat was neutral, whereas the old seat was evaluated as very uncomfortable. Also, neither backrest cushion was evaluated as comfortable (Table 13.5), so the various items on which S1 (the best of the two) could be optimized were localized.

13.7.1

INGRESS

AND

EGRESS

In between sitting tests, subjects carried out an ingress–egress task (Fig. 13.3) in which they were required to move to the window seat (i.e., the seat farthest away), sit down for a few seconds, and then leave the seat again. This was performed with and without carrying a small piece of hand luggage, as was observed in the field test. The purpose of this test was to collect data on ease of ingress and egress and the proper form and positioning of grips on the seats. In both tests data were collected by using video cameras and questionnaires. Questionnaires were used to obtain user information on the specific aspects of the seat that involved comfort. By interviewing the test subjects and using the LPD method, all subjects could indicate where discomfort or pressure points were experienced and how cushions should be changed. Objective data were collected by measuring seat characteristics and by submitting the seat cushions to special laboratory tests regarding their pressure-distribution quality (Fig. 13.4). All data were analyzed and discussed by experts in meetings where ideas to improve the benchmark S1 were generated. During those meetings the experts interpreted information from the test subjects that led to seat improvement ideas. One idea, for example, was to improve the sleeping possibilities by pivoting the seat around the axis to the front edge of the seat. This was suggested in combination with shifting the headrest to the front.

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FIGURE 13.3 Examples of ingress (A) and egress (B) used in the lab tests.

FIGURE 13.4 The system used in this project to measure pressure distribution objectively in different seats.

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FIGURE 13.5 The S1 seat, upright and tilted 5° backward.

13.8 MODIFICATIONS At this stage, two S1 seats were changed in order to evaluate the suggested modifications. Modifications were made to the lumbar support, the backrest angle, and the headrest. Eighteen subjects then compared the two modified versions of the S1 to the original S1. One version of the modified S1 was pivoted 5° backward (Fig. 13.5). The other version was not pivoted and had changes only to the lumbar support and headrest. The test consisted of three parts: upright sitting in a fixed position, ingress–egress, and free-posture sitting. Results from the test of upright sitting in a prescribed position showed that the pivoted version of S1 improved backrest cushion comfort (Table 13.6). The other test parts confirmed that the pivoted version of the improved S1 had the best results.

TABLE 13.6 Backrest Cushion Evaluation, Sitting Upright (Two Improved Seats Compared to the Benchmark (Original S1) Backrest cushion criterion Comfortable Angle backward Hardness of cushion Lumbar support Lumbar height Lumbar swell Upper back support Head support

Improved S1 (−5°) + ++ ++ + ++ + +/− +/−

Improved S1 (0°) +/− +/− + +/− + +/− +/− −

Original S1 +/− +/− +/− +/− +/− +/− −− −−

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163

REDESIGN PROPOSALS BASED ON END-USER OPINIONS

All of the tests and the analysis and interpretation of the data resulted in a final redesign proposal for the new S3 seat. The proposal focused on the following aspects: • • • • • • • • • • • • •

Seatback angle and bottom cushion angle Bottom cushion height from floor Seat depth Armrest (height, width, length, position, padding on surface, corners) Back shell including recessed area with respect to hip-to-knee space; shin space; and padding/form to protect knees and shin Horizontal spacing for occupants Bottom cushion contours Back cushion contours (horizontal and vertical, including lumbar support) Stiffness of back and bottom cushions Chamfer on the front part of the bottom seat Headrest dimensions Headrest wings Styling

The majority of the proposed changes to S1 were used to design the prototype S3. The most important redesign features of the S3 are highlighted below.

13.9.1

ANGLE

OF

SEATBACK

AND

BOTTOM CUSHION

The internal angle between seat and back was not changed. The entire seat was tilted backward 5°. The pivot axis was the top front edge of the seat cushion (Figure 13.6). By increasing the seatback and bottom cushion angle by 5°, the sleeping and resting quality of the seat should improve, based on data gathered from the user tests. In addition, more upper-body weight is transferred to the backrest, and therefore the amount of pressure on the buttocks is reduced. The reduction in hip-to-knee space and ingress–egress width could be a problem now, but this is counteracted by some of the alterations that follow.

S1 S3 5° tilt

FIGURE 13.6 Pivoting the seat around an axis at the front of the seat.

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ARMREST HEIGHT

Because the S1 armrest was generally evaluated as too low, the S3 has an armrest that is 0.03 m higher. This recommendation was based on an extra experiment with 26 new subjects. The experiment also showed that preferred armrest height does not appear to correlate to length, which is in accordance with the literature (Molenbroek 1994). It did show, however, a tendency toward a median preferred height.

13.9.3

BACKREST

The lab tests showed that the S1 lumbar support was too high and too thick. The lumbar support was therefore flattened and lowered, and the literature supports this idea. Reynolds (1993) states that highly contoured seat backs will not fit many people. Some will find such a lumbar support very good, others very bad, and only few consider it perfect. With flatter lumbar supports more people will appreciate the support without being extremely positive or negative about it. This was also found in the S1 testing and may be explained by the following thought. If passengers have the opportunity they will sit in a slightly slumped (relaxed) way (Han et al. 1998; Zhao and Tang 1994). This reduces or even flattens the lumbar curvature. Therefore, it is necessary to design the seat profile to fit a slumped sitting posture while still providing enough lower-back support to prevent long-term spinal stress (Zhao and Tang 1994). An extra benefit from flattening the lumbar support is that the seat cushion moves rearward, thus improving the ingress–egress width.

13.9.4

HEADREST

The folding line between headrest and backrest was lowered by 0.07 m, but that did not change the relative angle. Lowering the folding line translates the headrest horizontally to the front (Figure 13.7), resulting in more space for ingress and egress activities. This horizontal translation meets the requirements of 55% of the people who rated the original headrest as too far rearward. People sleep with their mouth open because of a headrest that is too far to the rear. By moving the headrest forward there is more space gained for ingress and egress.

approx. 2 cm 7 cm

folding line

FIGURE 13.7 Change in the headrest folding line. The 7 cm longer line to the right is the new one.

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FIGURE 13.8 Design of the high recess and optimal shin space of the new S3.

13.9.5

BACK SHELL

The overall back shell and back construction are reduced to a minimum to gain hip-to-knee space. By extending the recess in the back shell to the top, enough hip-to-knee space is created to counteract the reduction caused by the seat pivot. The hip-to-knee space fits the 97.5 percentile male to 2.5 percentile female segments of the target population. The recess area is constructed to give more shin space and thus facilitates leg stretching (Fig. 13.8). The ideal leg-stretching space was checked in the Ergomix, where passengers were mixed into a drawing of a seat and stretched their legs (Chapter 4, Figure 4.4). In this way, the ideal space under the seat in front of the passenger could be designed.

13.10

RESULTS: TEST OF THE PROTOTYPE SEAT

The prototype S3 was tested against the benchmark seat S1 using the same methods and long-duration tests as used earlier, but with 20 new subjects who did not know the new seat from the benchmark seat. This test was performed to see if the S3 seat design succeeded in scoring at least as comfortable as the S1 baseline seat. The S3 was made almost 0.05 m narrower than the benchmark S1 in order to place five S3 seats in one row. Both types of seat looked brand new. The experiments showed that the S3 seat was generally regarded as more comfortable than the S1. The average score given to the S3 seat on a scale from 1 (very poor) to 10 (perfect) was 7.3. The S1 received an average score of 6.2. This difference was statistically significant (p = 0.012, t-test for paired comparison). After 1 hour in the constrained upright testing position, 61% rated the S3 “comfortable” to “very comfortable,” compared to 22% for the S1. Similar results were found in the ratings of both seats for their suitability for sleeping and reading in the constrained upright testing position. The S3 seat was rated as “very comfortable” for reading by 61% of the subjects, whereas only 39% rated the S1 seat as “very comfortable.” In regard to sleeping, 28% of the subjects rated the S3 seat as “very comfortable,” but only 6% rated the S1 seat as “very comfortable” for sleeping. Given the choice of riding in either seat during 1 or 2 hours while commuting, 83% chose the S3. Table 13.7 shows the results of all questions in which the subjects were asked to choose between seats.

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TABLE 13.7 Ratings for Prototype (S3) and Benchmark (S1) Seats by 20 Subjects Sitting for 1 Hour Criterion

S1 (benchmark)

S3 (new)

6.2 16.7%

7.3* 83.3%

16.7% 27.8%

83.3% 72.2%

Entire seat Report mark General preference Forced choice General comfort Preferred for sleeping * significant, p = 0.012.

In 2003, the first trains were on the track and the actual passengers were interviewed on television. One of the first things mentioned by the passengers was that the seats were much more comfortable than in the old trains.

13.11 CONCLUSIONS Taking an existing seat as a starting point for the design of a new commuter train seat and applying end-user opinion research led to good end results. The scientific end-user test methods used to test the seats provided valuable data for the redesign.

FIGURE 13.9 An impression of the new interior with the new seats.

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The data from end users, with the added interpretation of experts, played a key role in the experiments, and the design of the new seat was primarily based on their opinions. An impression of the end results is shown in Fig. 13.9.

ACKNOWLEDGMENT The authors want to thank Long Island Railroad, Bombardier, and Multina for their wonderful support.

REFERENCES Han, S.H., Jung, E.S., Jung, M., Kwahk J. and Park, S. (1998) “Psychophysical methods and passenger preferences of interior designs.” Applied Ergonomics, 29(6): 499–506. Molenbroek, J.F.M. (2001) Human Scales for the Design and Evaluation of User Goods, Delft: Delftse Universitaire Pers (in Dutch). Reynolds, H.M. (1993) “Automotive seat design for sitting comfort.” In B. Peacock and W. Karwowski, eds., Automotive Ergonomics, London: Taylor & Francis. Zhao, J. and Tang, L. (1994) “An evaluation of comfort of a bus seat.” Applied Ergonomics, 25(6): 386–392.

through 14 Comfort an Emotion-Aware Office Chair C.J. Overbeeke, M.P. de Looze, P. Vink, and F.K. Cheung CONTENTS 14.1 14.2 14.3 14.4 14.5 14.6 14.7

Emotions in Sales.......................................................................................169 Emotional Reaction to an Office Chair .....................................................170 Results and Conclusion..............................................................................171 Controls and Office Chairs.........................................................................172 Emotions during Seating............................................................................173 Design and Emotion...................................................................................173 The Design Steps.........................................................................................173 14.7.1 Step 1: The Measurements...........................................................174 14.7.1.2 Step 1 Results ...................................................................174 14.7.2 Step 2: Emotional Aspects..........................................................175 14.7.3 Step 3: Pros and Cons..................................................................177 14.7.4 Step 4: Final Design.....................................................................178 14.8 Conclusions.................................................................................................179 References..............................................................................................................180

14.1

EMOTIONS IN SALES

Many industries have started to launch their products as emotion carriers, containers, or generators. They have realized that mere functionality does not sell any longer. Not only are customers not interested in the 54th new function, so many products have reached a level of technical perfection that it has become difficult to discriminate on that basis. (Overbeeke and Hekkert 1999, p. 5)

When two office chairs basically have the same functionality, we prefer the one that gives us a pleasant, desirable, or inspired feeling. The challenge is to design the appearance that evokes the emotions that are wanted by the chair’s users. These emotions are important because they primarily and strongly influence the decision 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

169

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FIGURE 14.1 The Emotion, an office chair made by Sitag. (Photo courtesy of Sitag.)

to purchase the chair (Holbrook 1985). Chairs that do not look good at first sight are not even tried in the showroom (Chapter 2). In the long run, the emotions experienced at first sight are likely to increase the pleasure of owning and using the chair after the purchase (Desmet et al. 2001). For designers, it is important to anticipate human emotions. One manufacturer even call its chair Emotion (Fig. 14.1). However, it is difficult to understand precisely how these emotions influence the purchase of a chair.

14.2

EMOTIONAL REACTION TO AN OFFICE CHAIR

As described in Chapter 1, Desmet et al. (2001) developed emocards to help study the role of emotions (Fig. 14.2). Sixteen cards show faces with different emotions, and a subject chooses the card that illustrates his or her emotion on seeing the product. This method was applied to a study of 15 office chairs (Looze et al. 2003). Seventy-nine subjects (28 male, 51 female) participated in the study. Fifty-nine subjects were office workers. Twenty were considered to be chair experts, because

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171

1 1 2

arousal

8

3

7

0

6

4 5

−1

−1

0

1

pleasantness

FIGURE 14.2 The 16 emocards developed by Desmet (2000) that help determine emotional reactions to products.

they were professionally involved in the evaluation or purchase of office chairs. Fifteen office chairs with wheeled undercarriage, armrests, and back and seat upholstered in black were evaluated. The chairs were different with respect to form, dimensions, and materials. The sequence of the 15 evaluations varied randomly across subjects. To measure the emotional responses at first sight (i.e., prior to sitting in the chair), the nonverbal self-report method using emocards was applied. The subjects had a few minutes to look at the chairs, but were not allowed to touch them. Then, each subject selected the emocard that best represented his or her actual emotional response to each chair. This process was repeated for each chair. Before the experiment, subjects also were asked to choose the emocard representing the response they wanted to experience (preferred response.) For each chair, the deviation of the actual emotional response from the preferred response within the circumplex was computed. The results for each chair were statistically compared (paired t-test, p < 0.05) with the average results across chairs.

14.3

RESULTS AND CONCLUSION

Because the results for the office workers were not significantly different from those of the expert group, the results are grouped together. Figure 14.3 shows the emotional response (the deviation from the preferred) of the subjects. Five chairs show an emotional response that deviates significantly from the average emotional response (across all chairs). This shows that the method discriminates, even with chairs that

Comfort and Design: Principles and Good Practice

emotion: deviation from preferred

172

0 A B C D E F G H I

J K L M N O

FIGURE 14.3 The deviation from the preferred emotional reaction for chairs A through O. Black bars indicate significantly better ratings than average; white bars indicate significantly worse ratings than average (p < 0.05). All vertical axes run from the minimum to the maximum values.

are all black. Therefore, for designers of office chairs trying to improve the emotional attractiveness of office chairs, this method can be useful.

14.4

CONTROLS AND OFFICE CHAIRS

The emotion at first sight, based on the appearance of the chair, is believed to affect the comfort experienced while sitting in the chair (Helander and Zhang 1997). Obviously, other factors such as the physical seating qualities will also influence the feeling of comfort. Another influential factor is the chair’s adjustability to individual needs. To enable adjustments, office chairs have many controls. Fully adjustable office chairs should, in principle, heighten comfort when working, but people use often these controls wrongly, or rarely. It is well known from ergonomic studies (Ong et al. 1988; Grandjean et al. 1983; Vink and Kompier 1997) that employees do not automatically adopt well-designed office furniture, such as adjustable chairs and desks. Even with an instruction program, results with respect to adjustment are usually limited to adjustments such as desk inclinations and document holders (Verbeek 1991). The end user is probably not aware of the need for another position of the chair, or may feel that actually changing the posture by adjusting the chair is too big a bother. Certain handles change different dimensions of the chair (Fig. 14.4). There are office chairs with controls for pneumatic seat height adjustment, tilt tension, tilt lock (eliminates tilt function when the chair is in an upright position), seat front–backward adaptation, backrest height and front–backward position, and so forth. Most people are not experienced enough in handling different dimensions separately (Djajadiningrat et al. 1996). An adjustable chair requires them to construct a mental model with many degrees of freedom, that is, to decompose a movement into its Cartesian components.

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FIGURE 14.4 Some controls of a simple office chair.

14.5

EMOTIONS DURING SEATING

Perhaps it is better to let the chair do all the work. Technology has reached the point where sensors in the chair can feel when a person is tired, and the chair can subsequently adapt its posture. The questions are what the chair should feel, what it should know, and what it should do with this information. These are the three basic questions discussed in an explorative study reported in the rest of this chapter.

14.6 DESIGN AND EMOTION Having said that emotions play an important role at first sight, as well as when using a product, the design process that anticipates emotions is more difficult. This chapter describes a design process with a focus on emotions. It is the first pilot study on the subject.

14.7 THE DESIGN STEPS People express their feelings by actions. If you ever met a really angry person, you know what is meant. The philosophy of the human–product interaction research and design of the work in this chapter thus concentrates on what people can do, know, and feel (Overbeeke et al. 2003; Wensveen et al. 2000). As a first step, an experiment was performed to analyze the current office work situation, testing whether the emotional state during office work was correlated with

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the sitting behavior. To this end, we measured the macromovements of the sitting subjects, as well as their emotional state using emocards (Step 1). The relevant emotional aspects were described, followed by a series of concept designs (Step 2). The pros and cons of the different designs were discussed with end users, ergonomists, and emotional design experts (Step 3). These comments became input for the end product: a conceptual chair that moves between states of emotion, according to the state the sitter is in and the task at hand (Step 4).

14.7.1

STEP 1: THE MEASUREMENTS

An experimental setup was arranged in the laboratory of the faculty of Movement Sciences of the Amsterdam Free University. Four subjects sat at a table with a computer in three types of office chairs, respectively. The table and chair were ergonomically correctly adjusted for each subject (Fig. 8.3, Chapter 8). The three types of chairs were 1. A fixed chair that could not be moved in any way by the subject 2. A synchro-chair — the seat and the back could be moved, but only simultaneously because they were in a fixed ratio to each other 3. A multidynamic chair whose seat and back could be moved independently Three types of recordings were made: general observations, specific recordings of macromovements, and changes in emotional reactions, using the emocards. Two cameras recorded the subjects’ movements during the whole experiment. The viewing angles were chosen so that the each subject was wholly in view all of the time. The four subjects (two male and two female students) did three sessions (one for each chair, randomized) that lasted 3 hours each, on three separate days. Their tasks were 45 minutes of typing a given text, 15 minutes of relaxed reading, 45 minutes of AutoCad drawing, 15 minutes of relaxed reading, 45 minutes of typing a given text, and 15 minutes of relaxed reading. The recordings were made three times. At the start, the subjects were asked about their first impression of the chair and how comfortable it seemed to them. emocards were used for each task after 15, 45, and 60 minutes. To finish, they were asked what their general impression of the chair was after each session. 14.7.1.2

Step 1 Results

Because the results are based on four subjects only, they should be seen as indicative of a general trend only. When looking at the videos, we noticed that the subjects’ legs were usually moving. We defined four positions of the legs: outstretched, straight down, slightly backward, and fully backward. We counted every transition between those positions as a macromovement. The results for the three types of chairs and the six consecutive tasks, summed over subjects, are shown in Table 14.1. The numbers are per 15-minute periods (because the reading took 15 minutes and the other tasks 45 minutes). For the fixed chair and the synchro-chair the data are as expected. After some time, the subjects grew tired and made more movements. With the fixed chair the

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175

TABLE 14.1 Number of Macromovements Fixed chair t 20

r 38

Synchro-chair c 22

r 34

t 46

r 80

t 23

r 61

c 24

r 52

Dynamic chair t 37

r 72

t 37

r 61

c 27

r 39

t 36

r 53

t = typing; r = reading; c = CAD

movements increased from 20 in 15 minutes to 80 in 15 minutes. The subjects moved more when reading (54 movements in 15 minutes) than in the other tasks (typing 33, CAD 12), probably because the reading task is less constraining. The dynamic chair invites more movement than the static chair. The emotional reactions did not differ much over time. Probably the test method is not suitable to this type of research or the number of subjects was too low.

14.7.2

STEP 2: EMOTIONAL ASPECTS

Step 1 showed that the frequency of macromovements changes over time and is related to the type of chair and to the task being executed. The question is, however, how should the chair get to know what it should adapt to? In other words, the chair should be aware of the office environment, on the one hand, and of the person sitting in it and his or her current task, on the other hand. The office environment and the required tasks were explored in several scenarios. This led to interesting themes. The chair could be an integrating factor within the office. It could also be the user’s guardian angel, and it could have different characters playing this role, from dominant to caring. Furthermore, the chair could be expressive in communicating the emotional state of the user to the rest of the office. Several of these themes were translated into design concepts and discussed with users and experts. Figures 14.5 through 14.9 show some concept drawings.

FIGURE 14.5 Concept bar. This chair adapts to the emotions: relaxed (left), concentrated work (middle), and short sitting work (right).

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FIGURE 14.6 Concept cylinder protector. This chair adapts to the level of concentration needed in the work. The right-hand position is for more concentrated work.

FIGURE 14.7 Concept spring. This chair could be a kind of stool (left), and then change into a fixed office chair (middle) or an easy-up chair (right).

FIGURE 14.8 Concept starfish chair. This chair invites you to sit, and it has the ability to close for concentrated work and open for more communication.

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FIGURE 14.9 Concept tilt. This chair can be used from different positions: for average work (left), for work where you can easily stand up (middle), and for more relaxed work (right).

14.7.3

STEP 3: PROS

AND

CONS

Based on the pros and cons mentioned by end users and experts, it was not yet clear what the requirements were for the design. For the time being, we chose two levels of communication to the environment (open or closed) and two levels of personal state (relaxed or concentrated) because these were seen in almost all situations. Furthermore, we wanted the chair to be caring and to be dominant only to prevent WMSD (work-related musculoskeletal disorders), for example, by stimulating movement. The chair should than have the technical capability to measure four resulting situations: 1. Concentrated and closed, for example when writing this text or during important telephone conversations. The user is sitting up straight and relatively still. The task is done individually and under high pressure. 2. Concentrated and open, for example when cleaning the desk or consulting colleagues. The user uses the chair infrequently and more as a leaning support, often rushing around. The high-priority task is done in collaboration with others under time pressure. 3. Relaxed and closed, for example, when surfing the Internet, checking e-mail, or reading. The user sits relatively still, straight, or shoved under the table. 4. Relaxed and open, for example, when taking a coffee break, or talking to colleagues in a Friday-afternoon atmosphere. The user moves a lot, is open to others, and generally leans back in the chair. In these four situations the chair should at least be able to measure (1) leaning forward; (2) leaning backward and its intensity; (3) the absence of macromovements; (4) nobody on the chair; (5) orientation toward the desk; and (6) distance to the desk. All of these measurements are technically feasible.

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14.7.4

STEP 4: FINAL DESIGN

Once the four situations have been described, a new concept was designed for a chair that reacts to the user and adapts itself to facilitate the four work situations. The final design is shown in Fig. 14.10. It adapts to the four work situations as follows: 1. Concentrated and closed: The chair gives a stable seat, whereby arm rests and back support are given. The chair shields users from the environment so as to heighten their concentration and to let their colleagues know they are not to be disturbed. 2. Concentrated and open: The chair supports standing and leaning. The seat is at an angle inclined to the front and fixed. 3. Relaxed and closed: The chair is wobbly and can be changed from straight up to inclining backward. It shields the user from the surroundings. 4. Relaxed and open: The chair is wobbly and can turn. The user can get in and out of the chair easily, and it offers great freedom of use. As indicated earlier, we decided to give the chair a caring character. This means, for example, that when a user pushes backward for a while, the chair will change its current position to the desired position. But caring also means being dominant sometimes. To prevent WMSD the chair will become dynamic (loosen the seat and become wobbly) and will thus stimulate the user to move when he or she has been sitting still too long. But caring also means obedient. When the chair wants to change its position, it can always be overruled by simply giving it a jerk. Figure 14.10 shows how such a chair could look. Along with the usual office chair possibilities, this conceptual design offers more. Of course the chair already

The arm rests can pivot and rotate

The wheels have a collective brake system

The screen offers privacy or openness

The seat can be adjusted in height and topple

FIGURE 14.10 The conceptual chair. (Design by Kin Fai Cheung, TU Delft.)

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Concentrated and Private

Concentrated and Open

Relaxed and Private

179

Relaxed and Open

FIGURE 14.11 The chair changes to different positions according to the sitter’s state and task at hand.

knows things (and might even be equipped with learning capacities), but it also has new capacities. The armrest can be retracted or turned down to serve as a legrest. A screen can shield the user from the environment. The chair itself is mounted on a spring so that it can wobble or, when the spring is deactivated, the chair is static. Figure 14.11 shows the different states of the chair for the different situations. The chair moves from one state to another, according to the situation at hand. In the concentrated and open situation, for example, the chair is high like a stool and does not support the arms or shield the head. When the situation is relaxed and open, the chair is low, turns away from the desk, and affords sitting in unconventional ways.

14.8 CONCLUSIONS The emotional reactions of end users to office chairs can be found by using emocards. Differences are shown even between office chairs that are all black. The conclusion from the exploratory study is that there are possibilities for letting the chair react to the user’s emotional state. This feature could be used to reduce WMSDs. For example, a chair may monitor the user’s state of well-being and convince the user to change his posture or to change to a different task to counter WMSD-related problems. Another application would be to have the chair act as an input device for communication devices such as a telephone or ICQ. The chair could detect a state of stress or concentration and communicate that to the telephone or computer system, which would enables these systems to filter incoming messages and limit them to the urgent or important. Finally, an interactive chair could support the user’s current state by changing configuration. When the user is highly concentrated, the chair could support that mode of working by shielding the user from his colleagues. This study is of an explorative nature, and it can aid further study of the relationship between the user’s state of emotion and chair adaptation to it. Further research is needed with respect to the way macromovements are related to comfort and state of emotion, and a better insight is needed into whether the four chosen options are the most functional in regard to tasks to be done at the office.

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REFERENCES Desmet, P.M.A., Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with added emotional value: Development and application of an approach for research through design.” The Design Journal, 4(1): 32–47. Djajadiningrat, J.P., Overbeeke, C.J. and Smets, G.J.F. (1996) “The importance of simultaneous accessible degrees of freedom.” Human Behaviour and Information Technology, 16(6): 337–347. Grandjean, E., Hunting, W. and Piderman, M. (1983) “VDT workstation design: Preferred settings and their effects.” Human Factors, 25: 161–175. Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.” Ergonomics, 40: 895–915. Holbrook, M.B. (1985) “Emotion in the consumption experience: Toward a new model of the human consumer.” In R.A. Peterson, W.D. Hoyer and W.R. Wilson, eds., The Role of Affect in Consumer Behavior: Emerging Theories and Applications, Lexington, MA: Heath, 17–52. Looze, M.P. de, Krause, F., Reijneveld, K., Desmet, P. and Vink, P. (2003) “Seat appearance and sitting comfort.” In Proceedings of the 15th Triennial Congress of the International Ergonomics Association and the 7th Joint Conference of the Ergonomics Society of Korea/Japan Ergonomics Society, Vol. 3: Product Design, Seoul: The Ergonomics Society of Korea, 632–635. Ong, C. N., Koh, D., Phoon, W. O. and Low, A. (1988) “Anthropometrics and display station preferences of VDU-operators.” Ergonomics, 31: 337–347. Overbeeke, K., Djajadiningrat, T., Hummels, C., Wensveen, S. and Frens, J. (2003) “Let’s make things engaging.” In M.A. Blythe, A.F. Monk, K. Overbeeke and P.C. Wright, eds., Funology: From Usability to Enjoyment, Dordrecht: Kluwer: 7–17. Overbeeke, C.J. and Hekkert, P., eds. (1999) Proceedings of the 1st International Conference Design and Emotion, Delft: University of Technology. Verbeek, J. (1991) “The use of adjustable furniture: Evaluation of an instruction programme for office workers.” Applied Ergonomics, 22: 179–184. Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics, 40(4): 435–449. Wensveen, S.A.G., Overbeeke, C.J. and Djajadiningrat, J.P. (2000) “Touch me, hit me and I know how you feel. A design approach to emotionally rich interaction.” Proceedings of DIS’00, Designing Interactive Systems, New York: ACM, 48–53.

a Comfortable 15 Toward Paint Scraper S.M. Eikhout, R.E. Bronkhorst, P. Vink, and M.P. van der Grinten CONTENTS 15.1 15.2 15.3 15.4

The Problem ...............................................................................................181 The First Ideas for Redesign .....................................................................182 Bahco Ergotools .........................................................................................184 The User Test Method.................................................................................185 15.4.1 Setup ............................................................................................185 15.4.2 Physical Load...............................................................................185 15.4.3 Goniometry ..................................................................................185 15.4.4 Trial of Strength...........................................................................186 15.4.5 User Friendliness .........................................................................186 15.5 Results.........................................................................................................187 15.5.1 Posture and Movement.................................................................187 15.5.2 Forces and Torque on the Wrist...................................................187 15.5.3 User Friendliness: Subjects’ Opinions..........................................187 15.5.4 Discomfort and Comfort..............................................................188 15.5.5 Qualitative Evaluation..................................................................188 15.6 Discussion...................................................................................................189 Acknowledgment ...................................................................................................190 References..............................................................................................................190

15.1 THE PROBLEM Painters are a high-risk group for health problems. According to European and Dutch data of the building industry, painters suffer from more complaints of the upper extremities than the control group in the construction industry (Arbouw 1997). Construction workers already show more health impairment than the general working population (Blatter and Bongers 1999). A study at the University of Iowa (Cook et al. 1996) also found a greater incidence of health complaints involving the upper limbs of painters, compared to construction workers. 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

181

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FIGURE 15.1 The traditional paint scraper that is now frequently used.

Frequent use of tools can lead to health complaints from the following risk factors: unfavorable postures and movements of wrists and shoulders, high torques, high repetition of movements or effort, excessive localized friction or pressure in the contact hand grip, vibrations, and high precision (Grinten 1999). According to Feggeler et al. (1992), a significant number of the complaints can be prevented by the ergonomic shape of tools. At present, all Dutch painters use the traditional triangular scraper (Fig. 15.1). However, the design of this tool could be improved and better adapted to the painter’s task and to the possibilities and limitations of the human body. Rhijn and Eikhout (1998) found hazardous forces and torque affecting the wrist during work with the triangular scraper.

15.2 THE FIRST IDEAS FOR REDESIGN Ideas for redesign were generated in a session with designers, human movement specialists, painters, and a person representing the Dutch sector organization for painters. Before this session, observations and measurements were made of the physical load and user friendliness of the traditional paint scraper. Professional painters were involved in these measurements. The main problems in working with the traditional triangular paint scraper were (Rhijn and Eikhout 1998): (1) frequent extreme wrist postures; (2) high forces of the arm, also due to the large moment arm; and (3) awkward postures in the back, shoulder, neck, and elbow. Several ideas were generated during the session on redesign ideas, and three were explored further (Figs. 15.2, 15.3, and 15.4). One idea was to use two hands to grip the paint scraper. Another concept was to reduce the distance between the scraping area and the hand. This reduces the moment arm, and thereby reduces the forces on the hand. The third idea was to change the angle between the grip and the scraper, which improves the position of the hand, wrist, elbow, and shoulder.

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FIGURE 15.2 An idea for improving the paint scraper: Lower forces are needed in each hand when two hands are used.

FIGURE 15.3 Reducing the distance between the scraping area and the hand reduces the moment arm, and thus the forces on the hand.

FIGURE 15.4 Changing the angle between the grip and the scraper can improve the position of the hand, wrist, elbow, and shoulder.

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Comfort and Design: Principles and Good Practice

15.3 BAHCO ERGOTOOLS These redesign ideas led to collaboration with Bahco Tools of Sweden. Bahco produces the so-called ergotool line, in which much attention is paid to ergonomics to arrive at comfortable hand tools. The ergotools have been developed in close collaboration with end users, following a scientific 11-point program (Bobjer and Jansson 1997). Essentially, the development program requires that operators are intensively involved. This 11-step program can be summarized as follows: After preliminary specifications are determined by interviewing and observing users (step 1), a market analysis (step 2) is performed. In step 3, background information is collected from papers, textbooks, and reports, followed by the design of a first prototype (step 4). Then professionals are exposed to the experimental prototypes (step 5) and improvements are defined in interviews based on research (step 6). A user test (step 7) is then completed by a wider selection of users in several countries. In step 8, the final design recommendations are made, followed by product specification (step 9). Another user test is performed in step 10 to prove that the tools work, and the product is launched. In step 11, more field tests are performed to gather data for further product improvement. The new scraper (Fig. 15.5) that is developed in the 11-step process has a blade of hard sintered metal, so that blade grinding is no longer needed. The shape of the handle is also different. The triangular scraper has the largest handle diameter close to the blade, whereas the new scraper’s handle is thickest close to the body. This reduces slip between hand and tool. The form of the handle is also better adapted to its use in the scraping task by improving the grip. This sounds wonderful: an ideal participatory design process and applause for a good, comfortable product! However, the effects of use and the end users’ opinions are unknown. Therefore, an extensive user test was conducted and will be described in the next paragraphs.

FIGURE 15.5 The new paint scraper developed in the 11-step program.

Toward a Comfortable Paint Scraper

15.4 15.4.1

185

THE USER TEST METHOD

SETUP

Twenty Dutch professional painters from seven different painting businesses volunteered to participate in this field study. The selection criteria required painters to have a large number of scrape activities during the test period and to have no history of health complaints. All subjects were males with 14 ± 11 years of painting experience; age 33 ± 12 years; height 1.82 ± 0.07 m; and weight 81 ± 11 kg. After an introduction, the painters used the new scrapers in their normal work for two to three weeks. After one week the subjects were visited for guidance, and the test period ended with a test day.

15.4.2

PHYSICAL LOAD

Physical load was measured by recording posture, movements, effort, and torque during scraping. Posture and movements were recorded by goniometry. Forces and torques were recorded by a trial of strength.

15.4.3

GONIOMETRY

Using goniometry (Biometrics, 1999), the exact position of the hand in relation to the lower arm is measured (Fig. 15.6). The registration of the wrist angle in degrees took place during a task that continued in time with a frequency of 20 Hz. This study measured flexion, extension, radial deviation, and ulnar deviation. Rotation of the lower arm hardly seems to occur and is therefore not dealt with

FIGURE 15.6 Measuring the position of the hand by goniometry.

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Comfort and Design: Principles and Good Practice

FIGURE 15.7 Trial of strength measurement setup.

in this research. In the field, goniometry took place during the performance of a standard task. It is assumed that the extreme wrist angle is reached at 75% of the subject’s range of motion of the wrist (maximum active wrist movement). This individual marginal value was determined for each subject. With this value the subject’s results were assessed so that the percentage of time in this posture was calculated and the difference tested within the group of subjects, using a paired t-test.

15.4.4

TRIAL

OF

STRENGTH

The strength to scrape was measured in two directions: horizontally (the push force) and vertically (the pull force). A special test surface was constructed (Fig. 15.7) to enable force measurement during a scrape task. The scrape motion was measured under multiple conditions, and the different torques were calculated. The torque was tested on significant differences using the paired t-test.

15.4.5

USER FRIENDLINESS

A questionnaire was used to record the opinion of the subjects. It consisted of questions on subjects’ descriptions, their opinions on comfort and discomfort, and their experiences in working with the traditional triangular scraper and the new scraper. The subjects completed the questionnaire under supervision of the researcher, and the results are presented in percentages or numbers of subjects. The paired t-test was used for statistical testing of differences. Finally, a qualitative evaluation was conducted to compare the handle of the new scraper with that of the of the triangular scraper. This evaluation is based on hand tool guidelines of Grinten (1999).

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187

15.5 RESULTS 15.5.1

POSTURE

AND

MOVEMENT

Nine gonio-measurements were analyzed. Percentages of the time in extreme postures are presented in Fig. 15.8. The differences were not significant. 7

mean time percentage

6 5 4 3 2 1 0 flexion

extension new scraper

radial deviation

ulnar deviation

traditional triangular scraper

FIGURE 15.8 Percentage of the time in extreme wrist position while working around different angles (n = 9) with the new scraper and the traditional scraper.

15.5.2

FORCES

AND

TORQUE

ON THE

WRIST

Seventeen subjects participated in the test under “dry” paint conditions. Eleven subjects participated under “burner” conditions in which the paint was first burned, which normally reduces the duration or force of paint scraping activities. The results are presented in Fig. 15.9. The mean forces under burner conditions were 17% lower on the new scraper than on the triangle. Without burner, the mean torque of the new scraper (n = 17) was 13.2 ± 7.1 Nm, and for the triangular scraper it was 14.7 ± 7.2 Nm. With burner (n = 11), the mean torque of the new scraper was 11.2 ± 4.5 Nm, and for the triangle it was 14.2 ± 5.8 Nm. These differences were significant. The torque of the new scraper, measured with burner, decreased 21% compared to the torque of the triangle with burner. Without burner, 10% torque reduction was found.

15.5.3

USER FRIENDLINESS: SUBJECTS’ OPINIONS

Twenty painters completed the questionnaire. The new handle was evaluated as “very well manageable” under separate conditions of dust, grease, and moisture by 74%, 71%, and 72% of the painters, respectively. The new scraper was considered to be

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Comfort and Design: Principles and Good Practice

Newton “dry” 70 60

new scraper traditional triangle

50 40 30 20 10 0

pull force “dry”

push force “dry”

pull force burner

push force burner

FIGURE 15.9 Mean pull and push forces (n = 17): “dry” and after treating the paint with a burner.

very comfortable in use by all subjects. Significantly less discomfort was experienced in the upper arm and in the joints of the fingers with the new scraper. Fewer blisters, less strength required for use, and a better hold were reported for the new scraper. The blades of the new scraper do not need to be ground, which is seen as an advantage, because grinding the old triangular scraper blades took much time. The sharpness of the new blades was very satisfying to 95% of the subjects. According to the painters, less damage to the surface had occurred while working with the new scraper. They even reported a higher productivity, which was confirmed by observations in which fewer scrape motions were recorded, and 74% stated that the quality of their work had improved. The painters evaluated the new scraper as safer than the triangle.

15.5.4

DISCOMFORT

AND

COMFORT

Perceived discomfort was reduced (Fig. 15.10) in working with the new scraper compared to the old scraper. In the upper arm and fingers a significant improvement in comfort was shown. Probably more importantly, 70% evaluated the new paint scraper as “very comfortable.” Regarding the handle, more than 90% of the painters gave a positive evaluation (Table 15.1). In the final evaluation, the new scraper was given 8.5 and the triangle 7.0 on a scale of 1 to 10. This difference was significant.

15.5.5

QUALITATIVE EVALUATION

Experts evaluated the handles of both scrapers on the following aspects: form enclosed force-transfer, material, “stick-slip,” form, and contact surface. Except in terms of the form, these factors were evaluated in favor of the new scraper. The shapes of both scrapers were evaluated equally.

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189

TABLE 15.1 Evaluation of the New Scraper Handle by Percentages of Subjects Approving (n = 20) Approval 90% 95% 100% 100% 100% 93% 100% 90% 84%

ra

rm

*

sh

ou

ld

er

/n

ec

k

Length of handle Diameter/circumference for hand Squarely section Hold on material Smooth finish Fit in hand Thickening of end of handle Distance of hand to handle Does not rub against wood/surface during scraping

fin

ge

rs

*

w

ris

t

up

pe

new scraper triangular

0

10

20

30

40

%

FIGURE 15.10 Local perceived discomfort (as percentage of the maximal discomfort of 20 painters) working with the traditional triangular paint scraper and the new scraper (* = significant, paired t-test, p < 0.05).

15.6 DISCUSSION Scraping results in unfavorable motions and high torques that cause a great deal of strain on the wrist (Rhijn and Eikhout 1998). The new scraper results in lower torques on the wrist, but improvement is still possible because it does not meet all the health limits of a daily load (Eikhout et al. 2001). The measured decrease in movement of the new scraper compared to the triangular scraper is mainly due to the decrease in pull and push forces. The distance from the grip to the contact surface is almost equal on the two scrapers. By decreasing this distance, the torque can be reduced

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Comfort and Design: Principles and Good Practice

further. However, it is uncertain whether this reduction will yield an optimum result, since there has to be room for the burner, the position of the fingers, and so on. It is also uncertain what the effect of this decrease will be on the limit forces. Both the traditional triangular scraper and the new scraper position the grip perpendicular to the blade, and in both scrapers the tool is held with a fist grip. The blade of the new scraper is convex-ground. The painter’s posture is mainly determined by the surface (i.e., inside or outside of a frame). Therefore, the painter has to adapt his posture to reach all spots. This might be an explanation for the small difference in wrist motion and posture when using the two scrapers. Working with extreme wrist angles carries a very high risk for health complaints and needs to be prevented as much as possible (Arbouw 1996). However, extreme wrist postures during scraping are probably inevitable because of dependence on the nature of the surface and the anthropometrical limitations of the human body. It might be possible to decrease the duration of extreme poses by modifying the shape of the grip and the position of the grip relative to the blade (Figs. 15.2, 15.3, 15.4). In the user test method applied, not all possible body postures during scraping are included. Some risks have possibly been excluded. In a given situation, the results may be positive for both scrapers in regard to the forces measured as well as the goniometry. This project evaluated only the short-term effects; it did not consider the long-term effects on the painters’ health. That would have to be done in a longitudinal study in order to reduce the risk of musculoskeletal injuries among painters and to benefit their health. Scraping places a high physical load on the painter. The new scraper makes his job easier and reduces physical load, compared to the triangular scraper. This is shown by results with the new scraper that demonstrate a 21% reduction in wrist moments, a 17% reduction in pull force, and some improvement of the wrist posture and wrist movement. Finally, taking into account the very positive evaluations by the end users and the positive qualitative evaluation with the health guidelines, the usability of the new scraper compared to the traditional one is a substantial improvement. Sales of the Bahco paint scraper continued to be very good after the project.

ACKNOWLEDGMENT The authors wish to thank Bahco Tools BV for providing the scrapers and the Board for Painters and Decorators for funding this research project.

REFERENCES Arbouw (1996) Arbouw-richtlijnen voor fysieke belasting in de bouwnijverheid, Amsterdam: Stichting Arbouw. Arbouw (1997) Bedrijfstakatlas. Arbeid en gezondheid bouwnijverheid, Amsterdam: Stichting Arbouw. Biometrics (1999) Operating Manual, Cwmfelinfach, Gwent, UK.

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Blatter, B.M. and Bongers, P.M. (1999) Work Related Neck and Upper Limb Symptoms (RSI): High Risk Occupations and Risk Factors in the Dutch Working Population. Hoofddorp: TNO Arbeid. Bobjer, O. and Jansson, C. (1997) “A research approach to the design of ergonomic hand tools. The 11-point programme.” In P. Seppälä, T. Luopajärvi, C.H. Nygård, and M. Mattila, eds., From Experience to Innovation. Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Helsinki: Finnish Institute of Occupational Health, Vol. 2, 193–195. Cook, T.M., Rosecrance, J.C., and Zimmermann, C.L. (1996) The University of Iowa Construction Survey. Iowa City, Iowa: University of Iowa. Eikhout, S.M., Bronkhorst, R.E., and Grinten, M.P. van der (2001) “Evaluation of a New Scraper.” Proceedings of the 45th HFES Congress 2001, Minneapolis: HFES, 722–726 (on CD-ROM). Feggeler, A., Yoo, J.W., and Hornung, V. (1992) Ergonomische Gestaltung von handgeführten elektromotorischen Arbeitsmitteln. Dortmund: Bundesanstalt für Arbeitsschutz. Forschungsbericht Fb 668. Grinten, M.P. van der (1999) Arbouw-richtlijnen voor fysieke belasting bij gebruik van handgereedschap en hanteren van verpakkingen in de bouwnijverheid. Hoofddorp: TNO Arbeid. Hall, Ch. (1995) Hand Function with Special Regard to Work with Tools. Stockholm: National Institute of Occupational Health. Arbete och hälsa 1995:4. prEN 1005-3 (1998) Safety of Machinery — Human Physical Performance Part 3: Recommended Force Limits for Machinery Operation. Brussels: CEN/TC 122. Draft March, 1998E. Rhijn, J.W. van and Eikhout, S.M. (1998) Ergonomische beoordeling van handgereedschap met aanzet tot herontwerp. Hoofddorp: NIA TNO.

of 16 Development a Handheld SteelFixing Tool J. Visser, T. König, I. Ruiter, and P. Vink CONTENTS 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8

Introduction.................................................................................................193 TyTecker and the Market.............................................................................194 Problem Definition .....................................................................................194 Approach.....................................................................................................195 Analysis ......................................................................................................196 Results of the Observations.........................................................................196 Results of the Interviews ...........................................................................196 Literature Results Concerning Static and Dynamic Loading ...................197 16.8.1 Working Posture...........................................................................197 16.8.2 Repetitive Movements .................................................................198 16.8.3 Ergonomics Guidelines: Wrist and Hand....................................199 16.9 Synthesis and Evaluation ...........................................................................201 16.9.1 Posture, Configuration, and Balance.............................................201 16.10 Design Proposal..........................................................................................203 16.11 Detailed Model...........................................................................................204 16.11.1 Usability Tests with the Model ...................................................204 16.12 Conclusions and Recommendations............................................................205 References..............................................................................................................205

16.1 INTRODUCTION One of the construction activities where working conditions certainly can be improved is rebar tying. In particular, the forward-bent working posture, the repetitive movements, and the cyclic character of the work increase the chance of discomfort and musculoskeletal injuries in the long run. The Dutch rate of sick leave in this profession is 7.9%, compared to 6.2% in the Dutch construction industry overall (CBS 2002).

0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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An innovative rebar tying system developed by the Dutch company TyTecker potentially solves several of these problems. However, the first and current design of the tying tool introduces several new issues concerning ergonomics and usability. A redesign was therefore initiated at TyTecker by the first author as a graduation assignment. The redesign process is described in this chapter.

16.2

TYTECKER AND THE MARKET

TyTecker, founded in 2000, is a relatively new player in the rebar tying market. The company has already developed an innovative and patented clip to fasten the rebar ties. The clip is the main source of income for TyTecker, with the tying tool being a necessary, but secondary, product — much like the business model of telecommunication providers. As a result, the tying tool itself can be sold nearly at cost, leaving room for optimization of ergonomics and usability. The tying solution that TyTecker developed is not the only one on the market. However, existing alternatives to the common tying tool have not succeeded in acquiring substantial market share and thus do not significantly improve working conditions. The perceived cost increase and less-than-optimal usability and reliability have limited the acceptance of these products by end users and tying companies.

16.3

PROBLEM DEFINITION

The large number of publications concerned with occupational health on construction sites (see From Experience to Innovation, Proceedings of the 13th Triennial Congress of the International Ergonomics Association, 1997) illustrates the need for improvement. Several studies (Broersen et al. 1991; Cook 1996; Smallwood 1997; Wakula et al. 1997; Ploeger 2000; Koningsveld 2002) show that working postures and repetitive movements are key problems in rebar tying, resulting in back injuries and musculoskeletal disorders of the upper extremities. Working postures are especially awkward when tying at floor level because this work requires prolonged extreme bending of the lower back (Fig. 16.1)

FIGURE 16.1 Bending forward during rebar tying is frequently observed.

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FIGURE 16.2 An old model of the TyTecker machine, which was improved in this project. One of the problems was that the old model was too heavy, and it took too much time to refill the tool with a new cartridge.

TyTecker’s tying tool — currently in the prototype phase — allows for an improved posture during floor rebar tying. However, floor tying represents only part of the tying work. Rebar tiers also tie in the vertical plane (walls, columns) and under special conditions (for instance, in tilted rebar planes and prefab tying). For these cases, the current tool is not the best solution. TyTecker recognized the opportunity to develop a compact, flexible, hand-held tool for various situations. The target was to develop a compact, hand-held rebar tying tool for use in walls, ceilings, and other situations. Key aspects of the new product are usability (operating and refilling the tool) and function integration (one design incorporating all components). Apart from the occupational ergonomics challenge, there’s a second, equally important aspect to the development of this new steel-fixing tool: the acceptance of the tool by the workers. Over the past years, several new tools claiming ergonomical operation have been introduced, but these still have a negligible market share and thus do not significantly contribute to better conditions in the trade (Fig. 16.2). According to the thesis of Jong (2002) and Chapter 4, reliability of operation and communication with target groups are key aspects in market acceptance of a product. Consequently, communication with workers during the development stage is an important source of design criteria for new tools and solutions to achieve successful implementation.

16.4 APPROACH The design approach used is based on the design theory developed at the Faculty of Industrial Design Engineering (Roozenburg and Eekels 1991; Marinissen 1993) and consists of an analysis phase followed by several iterations of synthesis and evaluation. In the analysis phase, both literature and field research were carried out. During the synthesis and evaluation iterations, the design was developed from spatial configurations, through concepts, to a detailed final proposal. Following the iterative and creative nature of the design process, further research was conducted when necessary during the development of the design.

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16.5 ANALYSIS Ergonomics literature on design guidelines was studied, ranging from whole body postural advice and anthropometrical data to overall suggestions on product safety or left- and right-hand use (Dreyfuss 1960; Buurman 1996; Fransson and Kilbom 1991; Garner 1992; Kapandji 1980; Radwin and Haney 1996; Woodson 1981). Where possible, different sources of data were compared to make a sound decision on a particular ergonomic design criterion. In addition to the literature research, field experts were interviewed. The interviews yielded insight into the factors that determine the success of a new product introduction. The major factor in the highly conservative construction industry is workers’ opinion on the tool. In addition to this insight, an article in Harvard Business Review showed the importance of actual on-site research to the success of new product development (Leonard and Rayport 1997). Therefore, the actual needs, opinions and working habits of the steelfixer, as well as the currently used tools, were investigated during two on-site observation sessions.

16.6

RESULTS OF THE OBSERVATIONS

The observations showed the working posture to be a major concern (bending the lower back and lifting heavy loads), but repetitive movements of the wrist are a problem as well. The video material obtained during the two observations revealed several remarkable issues: •

•

•

Steelfixers leave their equipment in odd places, and every worker has his own tying tool. When the tool is not in use, they store it in a variety of locations: on the boarding, on a solid floor, in the back pocket of their work clothing, or suspended from a do-it-yourself ring. The tool is used for other tasks than just tying rebar. During the observations, the steelfixers regularly used the tool as a hammer, banging against rebars that were not correctly in place. The steelfixers need a free hand to manipulate the work. Just before a tie is made, steelfixers sometimes need to adjust a rebar or to support a bar in order to be able to make the connection. In these cases they need one hand to manipulate the rebars, holding the tying tool in the other one.

These observations are important signals for the tool that is being developed: The worker should be able to suspend it from a belt or otherwise put it away, the tool must be operable with one hand, and it must withstand rough treatment (reliability).

16.7

RESULTS OF THE INTERVIEWS

The interviews revealed useful user experiences with — and opinions on — the other tying solutions. From the interviews, several conclusions could be drawn with respect to TyTecker’s tying tool:

Development of a Handheld Steel-Fixing Tool

•

•

•

•

•

197

The tool should be compact. Because rebar tiers use one hand for materials manipulation, it is important that the tool can be operated with just the other hand. Tiers also preferred a small-sized tool so they could suspend it (e.g., from a belt) when it is not in use. The tool should be lightweight. This requirement seems straightforward, but it is of vital importance. Because the rebar tier uses the tool for long periods of time, tool mass is a key usability aspect. Reliability is important. At one of the observed construction sites, a competing brand of tying tool (Drillfix®) was present. The six available tools were not in use, however, because several of them malfunctioned. The defects caused the rebar tiers to abandon those competing tools. Because it has a major influence on user acceptance, reliability is a major concern for the new TyTecker tool. The tool should be easy to operate. Key manipulations with the tool should be easy to understand and perform. Refilling the tool should require the minimum number of steps. Adequate grip size and other design aspects allow the rebar tier to have a comfortable grasp of the tool. Good after-sales service should be provided. This conclusion has no direct relation to the tool design, but it seems to be just as important as instance reliability in terms of user acceptance. A fast, attentive, and effective repair service and after-sales department have established a positive image of the TyTecker brand within the trade.

16.8

LITERATURE RESULTS CONCERNING STATIC AND DYNAMIC LOADING

The two main factors determining the on-site working conditions of rebar tiers are working posture and the repetitive movements of the wrist and arm.

16.8.1

WORKING POSTURE

The main physical loads affecting a steelfixer are of a static nature. Rebar tying requires significant bending of the lower back, reaching out in awkward positions, and (to a lesser extent) kneeling. Steelfixers are exposed to long periods of working in one position (Fig. 16.1). Several sources in the literature provide guidelines for the maximum allowable bending of the lower back. Generally, such extreme postures should be avoided (Dul and Weerdmeester 2001). If bending is necessary, only slight bending of the back results in significantly less risk of lower-back pain (Bongers et al. 2000). If workers have to bend their lower back for more than 5% of the working time (half an hour per day), they have a 50% higher risk of developing lower-back injuries (Bongers et al. 2000). Vink et al. (1994) suggest that a 20° flexion of the back should be allowed for 20-minute periods at most. Flexions between 20 and 60° are acceptable only for

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periods shorter than four minutes. It is clear from these sources that a working posture that requires bending of the lower back should be avoided as much as possible. If necessary, the flexion should be minimized, both in angle and duration. Even though these results apply mainly to floor rebar tying, they are also of interest for cases of tying in the vertical plane, or on tilted rebar planes. Apart from bending the lower back, steelfixers regularly have to stretch out to hard-to-reach tying spots, or kneel when the tying takes place closer to floor level. Twenty inches (0.5 m) is suggested by Dul and Weerdmeester (2001) as the radius of the reach envelope in which the majority of manipulations take place. The Dutch labor inspection authority emphasizes the individual nature of reach envelopes and advises workers to perform tasks close to the body when forces must be exerted. No further specification on close is given, but the 0.5 m suggested by Dul and Weerdmeester can be taken as a reference. Furthermore, dexterity is important when reach envelopes are concerned (the human lateral reach exceeds the medial reach).

16.8.2

REPETITIVE MOVEMENTS

A second problem in the steelfixing profession is posed by the repetitive movements of arm and wrist necessary to make a tie. Rebar tying requires a combination of precision and force exertion. It is, therefore, a job with a high risk of repetitive strain injuries (RSI). From the field observations, the average time needed to make one connection was 3.8 seconds (Table 16.1). This is a repetitive movement, especially considering the fact that ten or more consecutive ties are made regularly. Because the time needed to make one connection is mainly determined by outside pressure (deadlines and supervisors), an improvement is not likely to relieve the repetitiveness of the work. The second factor, posture during the tying movement, certainly offers room for improvement. The competing tying tool Max Rebar Tier replaces the combination of pinching and twisting that is inherent in the current working method with positioning the tool and pulling a trigger. These actions do not require a combination of force and precision, nor do they rely on twisting the arm and wrist. TyTecker’s tool should follow this direction, because it ideally combines low-precision positioning with little force exertion, plus a simple actuator, to make a rebar connection with the clip.

TABLE 16.1 Estimated Time Needed to Make a Tie Observation Observation Observation Observation Observation Observation Total

1 2 3 4 5 6

Number of ties 8 5 3 6 22 13 57

Elapsed time (s) 27 27 11 23 71 55 214

Time per tie

3.8

Development of a Handheld Steel-Fixing Tool

16.8.3

ERGONOMICS GUIDELINES: WRIST

AND

199

HAND

Whereas the field observations yielded important real-life information, a number of publications in the human factors and design literature provided useful anthropometrical data for tools in general, and specifically for the TyTecker product. The results are described below. •

•

Balance, mass, and forces To ensure easy manipulation of the tool, it should be well balanced. Balance here has two components: center of gravity and the working lines of forces. The center of gravity should be as close as possible to the center of the grasping hand. Ideally, the center of gravity also lies on the neutral axis of the lower arm (Radwin and Haney 1996; Woodson 1981). The mass of power tools is experienced as “just right” when it is in a range from 0.9 to 1.75 kg (9–17.5 N) (Radwin and Haney 1996). The mass should not exceed two kg, as benchmarked against competing products. Even though Eikhout and Koningsveld (2002) suggest four kg as the maximum weight of a power tool, this seems rather heavy compared to the mass of common battery-powered tools (average 2 kg). The forces that act through the tool upon the hand and arm of the steelfixer would ideally coincide with the working axis of the arm (Radwin and Haney 1996). If this is not possible, the force axis should be parallel to the working axis of the forearm. Because of the low forces involved in TyTecker’s system, this is an acceptable alternative. Grip design Several guidelines concerning grip design have been found, covering the grip’s angle, shape, and geometry. For the steelfixer to be able to hold the tool with a neutral wrist position, the grip should be angled at 15° (Fig. 16.3). For a power grip Bullinger and Solf (1979) suggest a hexagonal or foursided design, with a cross-section that slightly increases toward the middle of the grip. These basic shapes suggest a preferred orientation for holding the tool and thus increase ease of operation. The corners of the grip shape should be rounded. The straight sides of the grip should follow the finger digits of a bent hand (Bullinger and Solf 1979). To make a sound decision

FIGURE 16.3 The grip angle for neutral wrist position between the underarm and the axis through the hand (Dreyfuss 1960).

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TABLE 16.2 Anthropometrical Data for the Grip Derived from Five Sources Dreyfuss Grip length width of hand (+ thumb) width of hand (− thumb) …bent

p2.5 94 91.3 92.7

p50 104.1 88.9 101.4

Molenbroek & Dirken p97.5 114.3 96.5 110

p5 102.8

Dreyfuss Grip diameter Diameter at the end in the middle

p2.5 40.6

p50 45.7

p50 111

p95 119.3

Bullinger & Solf p97.5 53.3

p5

p50

p95

18 28

22 32

28 38

Garner p5

p50

p95

80

90

95

Fraser 40–50*

Molenbroek & Dirken Switch pointing finger width

p5 17.4

p50 19

p95 20.7

p = percentile; lengths in mm *diameter 50 mm, 5% less force Derived from Bullinger and Solf (1979); Fraser (1980); Dreyfuss (1960); Garner (1992); and Molenbroek and Dirken (1986).

•

on the target values for the length and cross-section of the grip, several sources of anthropometrical data were compared (Table 16.2). Comfortable wrist angles Because of the various steelfixing situations, the worker will in some cases have to operate the tool with an angled wrist. To determine which deviations and angles are acceptable during product use, six sources were compared and evaluated (Table 16.3).

TABLE 16.3 Six Sources Used to Derive Comfortable Wrist Angles for the Tool Design Kapandji (1980) Dreyfuss (1982) Houy (1983) Landstra (2000) Lange* Lange*

Maximum angles p2.5/p50/p97.5 p5/p50/p95 Estimates Maximum angles Comfortable angles Drawn steelfixer tool angles

*Both mentioned in Buurman (1996).

Ulnar deviation 15 15/27/40 22/30/40 20 20 0 10

Radial deviation 45 15/66/70 14/22/30 30 30 0 20

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•

•

201

Left-hand and right-hand use The design of the tool should facilitate both left-handed and right-handed workers, because a significant portion of the target workforce is left-handed. To achieve this versatility, the tool can be designed to be symmetrical in the vertical plane (Bauer and Schmauder 1995). This way, balance, working axis, and operation are identical for left- and right-handers. Product switches To determine the minimum size of the switches to be used in the tool, the width of the index finger (as suggested by the Dutch DINED tables) is taken and increased to accommodate for gloves (Molenbroek and Dirken 1986). The exact values are presented in the last row of Table 16.2. On top of the previously mentioned aspects of the tool’s design, several other influences that were mentioned in the literature should be taken into account: product noise and vibration, dust, weather, and temperature.

16.9

SYNTHESIS AND EVALUATION

Results from the observations, the interviews, and the literature were the input for the design process. In a systematic series of idea generations and evaluation, the fixing tool evolved from spatial configuration to a product design, including details on materials, color, and mechanical components. This iterative process can be described along with the resulting design, using photographs of the detailed model to discuss the features of the tool. An evaluation of the design, including an on-site usability test, concludes this section.

16.9.1

POSTURE, CONFIGURATION,

AND

BALANCE

The process can be divided into four main stages, in which the three essential design aspects — working posture, spatial configuration, and tool balance — were covered. The first stage identified the functional components, which together form the actual tying tool. Using mock-ups of these components, many configurations were generated and finally clustered into four typological categories. These four basic configurations (Fig. 16.4) were then evaluated using a subset of the ergonomic guidelines, which resulted in two promising basic configurations: a pistol grip type and a grip-on-top type (parts (A) and (B) of Fig. 16.4, respectively). These configurations were taken as the starting point for an analysis of the center of gravity with respect to the grasping hand. This product aspect is highly important, because it determines the ease of manipulation of the tool. Using mass measurements of the components of similar products, resulting torques exerted on the grasping hand center were calculated for several solutions. The solution with optimum balance was selected for both basic configurations. With the layout for both configurations clearly determined, focus shifted to the ease-of-use of the tool during the third stage of the development. Special attention was paid to the process of (re)filling the tool with tying clips, a key aspect in the usability of the tool and thus essential for its success. The design of the battery pack and the controls, and the overall styling, were also explored. The resulting two draft

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FIGURE 16.4 Mock-ups of four typological categories composing the basic parts of the tool: the grip, the engine, the battery, and the refill compartment. The refill compartment is the tube, the grip is in (D) shown between the refill compartment and the battery.

designs were evaluated on the criteria from the program of specifications and were studied in computer simulation. The working postures during operation were evaluated using the Anthropometric Design Assessment Program System (ADAPS) (Fig. 16.5), a mannequin-based

FIGURE 16.5 Two sample images of working postures with the new tool, made with ADAPS.

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203

computer simulation tool developed by the Faculty of Industrial Design Engineering (Ruiter 1996). The evaluation and posture analysis showed the pistol grip concept to be a better alternative than the grip-on-top concept. Postures with the pistol grip configuration were more in keeping with the ergonomic guidelines referred to earlier.

16.10 DESIGN PROPOSAL In Fig. 16.6 the final proposal is presented. The main characteristics of the design are discussed below (the numbers correspond with those in Fig. 16.6). 1. Adjustable tying head The head of the tool can be adjusted (in two positions) to suit tying work from ground level to above eye-level. 2. Main body shells The main part of the tool consists of two injection-molded polymer shells that hold all other parts. The grip is designed according to the ergonomic guidelines described earlier. 3. Sliding refill door For easy access to refill the tying tool, the upper (silver) part of the tool slides back, revealing the internal clip holder where new clips can be inserted. 4. Reversible battery pack The battery pack can be mounted on the tool in two orientations: facing forward or facing backward. This way, the tool can be adapted to specific situations (e.g., confined spaces).

FIGURE 16.6 Photographs of the model of the design (see text for an explanation of the numbers in the left photograph). Right a backward-side ward view, left a front-side view of the steel-fixing tool showing the tying head.

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5. Operating switch The switch used is a dedicated design, based on a standard off-the-shelf model. To accommodate the drive system, the switch has to be smaller in size than the standard model. 6. Wrist or security cord To allow the steelfixer to suspend the tool when not in use, a cord is provided. Apart from this function, the cord also communicates the brand image.

16.11 DETAILED MODEL As shown in Fig. 16.6, a detailed, true-to-scale model was made. Using the prototyping facilities at the Faculty of Industrial Design Engineering, the model was handbuilt in a six-week period with wood, metals, polystyrene sheet, and several other plastics. The model has a functional tying head and sliding door, because the aim was to test the usability of these two main aspects.

16.11.1

USABILITY TESTS

WITH THE

MODEL

The model was tested by professionals in rebar tying during a small-scale usability session. Because the test took place on an actual construction site, time and accommodations were limited. The modest setting, unobtrusive video equipment, and mainly open-ended questions made a more natural setting. Seven rebar tiers participated, and five of these steelfixers were specifically interviewed on the refilling process. Three workers performed common tasks, such as positioning or adjusting the head. The results of the test are summarized in Table 16.4. Although the user test was simple, some very useful insights were achieved: •

•

Positioning is easy. None of the steelfixers had a real problem with the positioning of the tool on a rebar. Two positioned the head correctly without any help. One subject discovered later how the positioning can be improved, after a closer look at the tying head. Another subject discovered the purpose of the indentation on the battery pack without specific clarification. It is not clear how to adjust the tying head. No worker understands immediately the way the adjustable head works. The icons designed to clarify the position of the head only seem to increase confusion. Clearly, this part needs additional development and design.

TABLE 16.4 Results of the Usability Test in Tabular Foam Task Positioning Adjusting head Refilling sliding open Refilling filling clips

n 3 3 5 3

1 attempt 2 0 5 0

>1 attempts 1 0 n/a 2

Result + − ++ +/−

Development of a Handheld Steel-Fixing Tool

•

•

205

Refilling: Opening the sliding door is easy. The first step in refilling the tool poses no problem to the tiers. They all recognize the way the door opens and act accordingly. Refilling: Placing the clips is more difficult. The second step appears to be less easy to understand, but after a while, one of the rebar tiers gets the idea and starts to explain it to the others. The clips require a specific orientation when refilling the tool, which is not obvious. It is necessary to clarify the orientation in the design of the clip holder.

16.12 CONCLUSIONS AND RECOMMENDATIONS This is a good example of how it is possible to design a comfortable hand tool. The attention to comfort has many consequences for the process. Apart from the strong user orientation and user tests, ergonomics knowledge is used in connection with weight, balance, whole-body postures, grip requirements, and anthropometrics. Also, emphasis on how the tool should be used (refilling, view of the work, the disadvantages of older models) is taken into account.

REFERENCES Bauer, W. and Schmauder, M. (1995) “Lefthanders and product design.” In Proceedings of the IEA World Conference 1995, Rio de Janeiro: Associação Brasileira e Ergonomia, 536–539. Bongers, P.M., Hoogendoorn, L. and Heuvel, S. van den (2000) Risk Factors for Lower Back Injuries: Results of a Longitudinal Study, Den Haag: Elsevier bedrijfsinformatie (in Dutch). Broersen, J.P.J., Weel, A.N.H. and Dijk, F.J.H. van (1991) Reference Guide to Occupational Health, Presented per Profession, part 2, Amsterdam: NIA (in Dutch). Bullinger, H.-J. and Solf, J.J. (1979) Ergonomische Arbeitsmittelgestaltung I — Systematik, Dortmund: Bundesanstalt für Arbeitsschutz und Unfallforschung. Buurman, R. den (1996) Design Ergonomics, Delft: Delft University of Technology (in Dutch). CBS Statline, sector data in construction industry (SBI ’93:45a) and rebar tying (SBI ’93: 94–99), www.cbs.nl May 2002. Cook, T. et al. (1996) Characteristics of Injuries and Illnesses Resulting in Absences from Work, 1994, Washington, D.C.: Bureau of Labor Statistics, U.S. Department of Labor. Dreyfuss, H. (1960) The Measure of Man, New York: Whitney. Dul, J. and Weerdmeester, B.A. (2001) Ergonomics for Beginners, London: Taylor & Francis. Eikhout, S.M. and Koningsveld, E.A.P (2002) “Designing hand tools.” In P. Voskamp, P.A.M. van Scheijndel and K.J. Peereboom, eds., Handboek Ergonomie 2002, Alphen aan den Rijn: Kluwer, 337–345. Fransson, C. and Kilbom, Å. (1991) “Tools and hand function: The sensitivity of the hand to external surface pressure.” In Y. Quéinnec and F. Daniellou, eds., Designing for Everyone: Proceedings of the 11th Congress of the International Ergonomics Association, London: Taylor & Francis, 188–190. Fraser, T.M. (1980) “Ergonomic principles in the design of hand tools.” Occupational Safety and Health Series No. 44. Geneva: International Labour Office. Garner, S. (1992) Design Topics: Human Factors, Oxford: Oxford University Press.

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Houy, D.R. (1983) “Range of joint motion in college males.” Proceedings of the Conference of the Human Factors Society ’83, 1: 374–378. Jong, A.M. de (2002) Improvement of Working Conditions at the Construction Site, Delft: University of Technology (Ph.D. thesis, in Dutch). Kapandji, I.A. (1980) Biomechanics of the Human Body: Part I, The Upper Extremities, Utrecht: Bohn, Scheltema & Holkema (in Dutch). Koningsveld, E.A.P. (2002) Rebar Tying, Ergonomic Aspects, Hoofddorp: TNO Work and Employment (confidential). Landstra, R. (2000) Operator Comfort in Forklift Truck Design, Delft: Delft University of Technology. Leopard, D. and Rayport, J.F. (1997) “Spark innovation through empathic design.” Harvard Business Review, Nov./Dec.: 102–113. Marinissen, A.H. (1993) “Information on product use in the design process.” In Ergonomics in a Changing World: Proceedings of the 29th Annual Conference of the Ergonomics Society of Australia, Canberra: Ergonomics Society of Australia, 78–85. Molenbroek, J.F.M. and Dirken, J.M. (1986) Dutch Body Measurements for Design, DINEDtable (3rd version), Delft: University of Technology, Faculty of Industrial Design Engineering (in Dutch). Ploeger, A. (2000) Work Related Disabilities in the Construction Industry, Amsterdam: EIB (in Dutch). Radwin, R.G. and Haney, J.T. (1996) An Ergonomics Guide to Hand Tools, Fairfax: American Industrial Hygiene Association. Roozenburg, N.F.M. and Eekels, J. (1991) Product Development: Structure and Methodology, Utrecht: Lemma (in Dutch). Ruiter, I.A. and Vaart, A.J.M. van der (1996) “Use of the ADAPS computer man-model by expert and novice users—A pilot study.” In S.A. Robertson, ed., Contemporary Ergonomics 1996. Proceedings of the Annual Conference of the Ergonomics Society, London: Taylor & Francis, 136–141. Smallwood, J.J. (1997) “Ergonomics in construction.” In Proceedings of the 13th Triennial Congress of the IEA, Tampere, Finland: 184–187. Vink, P. and Dul, J., eds. (1994) Physical Strain during Labor. Legislation and Solutions. (Lichamelijke belasting tijdens arbeid. Wetgeving en oplossingen), Zeist: TNO/ Uitgeverij Kerckebosch, 161. Wakula, J., Wimmel, F., Linke-Kaiser, G., Hoffmann, G. and Kaiser, R. (1997) “Ergonomic analysis of load on the back in concrete work.” Proceedings of the 13th Triennial Congress of the IEA, Tampere, Finland: 191–193. Woodson, W.E. (1981) Human Factors Design Handbook, New York: McGraw-Hill.

Effects 17 Comfort of Participatory Design of Screwdrivers S.M. Eikhout, P. Vink, and M.P. van der Grinten CONTENTS 17.1 17.2

Introduction ................................................................................................207 Method........................................................................................................209 17.2.1 Health and Discomfort Measurements........................................211 17.2.2 Productivity Measurements .........................................................212 17.2.3 End-User Opinion........................................................................212 17.2.4 Statistics .......................................................................................212 17.3 Results ........................................................................................................212 17.3.1 Health and Discomfort ................................................................213 17.3.2 Productivity ..................................................................................213 17.3.3 End-User Opinion........................................................................213 17.4 Discussion ..................................................................................................213 17.4.1 Health ...........................................................................................214 17.4.2 Productivity ..................................................................................215 17.4.3 Comfort ........................................................................................215 17.4.4 General Observations...................................................................215 17.5 Conclusions ................................................................................................216 Acknowledgment ...................................................................................................216 References..............................................................................................................216

17.1 INTRODUCTION The requirements put on companies that make hand tools have increased considerably. Nowadays, products should have a specific added value, should be focused on individual needs, should be safe and user friendly, and should even have a wow! effect. One way to develop unique products is to have them be highly comfortable in use. Ergonomics especially could be of great value in tuning products to the needs of users (Vink and Koningsveld 2000). For companies making hand tools, user discomfort and the need for ergonomically designed hand tools present an opportunity. The use of hand tools (such as screwdrivers) 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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could cause discomfort during work. These feelings of discomfort can reduce the efficiency and job satisfaction of workers (Fellows and Freivalds 1991). According to Chao, et al. (2000), the use of hand tools can also cause musculoskeletal disorders. In industries such as poultry processing and automobile upholstering, where hand tools are used extensively, upper-extremity disorders are much greater than the average (McGorry 2001). There is a need, therefore, for better hand tools that reduce discomfort. Interviews among 16 successful small- and medium-sized enterprises making professional products (products used in work) that were nominated for the 1997 European Design Prize (Thackara 1997) showed that these enterprises invest in ergonomics (Table 17.1). Approximately 16% of their total R&D budget was dedicated to ergonomics. However, there is a question as to whether these kinds of investments pay off and contribute to health, productivity, and comfort improvement. The hypothesis of this study is that investment in ergonomics has no effect on health, productivity, and comfort when using a hand tool. TABLE 17.1 Attention to Ergonomics in the R&D Budget for the Product Design Process of 16 EU Companies Developing and Producing Products Main product Headphones Prostheses

Number of employees 450 300

Country Austria

% R&D for ergonomics 10

UK

10

Demolition equipment Kitchen furniture Gardening tools Communication for control rooms Welding helmets

45 480 4000 350

Sweden Germany Finland Austria

30 5 15 2

150

Sweden

10

Hand tools Wheel loaders Backpacks Brain scan helmets

200 3000 1300 25

Sweden UK France Finland

50 10 50 2

>1000 300 230 445 220

UK Austria Norway Austria Ireland

10 6 35 5 10

Palmtop computers Access control systems Seats Spectators Electronic payment systems From Polling (1999).

Ergonomics research Acoustics, anthropometrics of the ear Microprocessor tests, shape measurement of the human body User tests, control logistics Anthropometrics, user tests Balance, user tests User interface tests Airco, visibility, anthropometrics Contact, user tests Cabin ergonomics, entry tests Wearing tests Head anthropometrics, usability tests Hardware and interface tests Keyboard design, user tests Seat and design research Balance, handle, user tests Keyboard design, information logistics

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FIGURE 17.1 One of the ergonomically designed screwdrivers. In the area close to the metal it has a smaller diameter to enable precision tasks.

To test this hypothesis, an ergonomically designed product (a Bahco screwdriver set) was compared with another screwdriver set that is also well known in the professional market, has a comparable price, and was not ergonomically designed. In this case, ergonomically designed means that an 11-step program (Bobjer and Jansson 1997) was followed. In this program it is essential that operators are intensively involved. The 11-step program may be summarized as follows: After a preliminary specification is made by interviewing and observing users (step 1), a market analysis (step 2) is conducted. In step 3, background information is collected from papers, textbooks, and reports, followed by the design of a first prototype (step 4). Then professionals are exposed to the experimental prototypes (step 5) and improvements are defined in interviews based on research (step 6). Another user test (step 7) is undertaken by a wider selection of users in several countries. In step 8, the final design recommendations are made, followed by product specification (step 9). In step 10 another user test is performed to prove that the tool works, and the product is launched. In step 11, more scientific tests are performed to gather data for further improvement of the product. The control set of screwdrivers did not follow this 11-step program. There are some important differences between the ergonomical screwdriver and the control. For instance, the ergonomical screwdriver grip is made of a special material that immediately matches the temperature of the user’s hand, and it has a high friction coefficient relative to other screwdrivers. The diameter is larger at the handle end to support forceful use, but in the area close to the metal it has a smaller diameter to enable precision tasks (Fig. 17.1). The ergonomical set is also color-coded. Every type of screwdriver in the set (Phillips-head, slotted-head, etc.) has a different color (Fig. 17.2).

17.2 METHOD As discussed by Arisz and Kanis (1999), under strict conditions and for comparison within a subject it is better to study fewer subjects thoroughly than a large number under varying conditions. To test the hypothesis, eight subjects used both sets of screwdrivers (the ergonomical set and the control set) on a standardized task. Subjects were not familiar with either screwdriver set and were not informed about the background. The subjects (average age 20 years) were students in their last year of automotive maintenance study. Manually operated (nonpowered) screwdrivers are still often seen in this sector. All subjects had at least 3 years of experience working intensively with hand tools, including nonpowered screwdrivers.

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FIGURE 17.2 The ergonomically designed screwdriver set.

Health and discomfort, productivity, and end-user opinion were evaluated during and after a standardized task (Fig. 17.3) and compared within one subject. The standard task was screwing 24 screws into a wooden object. The screws were of different types and sizes (Phillips-head screws of 3.5 mm and 4.5 mm and slotted-head screws of 4.0 mm and 5.0 mm) and had to be fastened into drilled holes (2.5 mm diameter, 30 mm deep) in a wooden object. This object had exactly the same dimensions in all situations. Twelve screws had to be screwed in forward (screw horizontal) and twelve downward (screw vertical), all in front of the body at elbow height, while the subjects were seated in a prescribed way on a fixed seat. The screwdrivers were positioned in a box on a low table to the left of the subject. The subjects had to replace the screwdrivers in the box after using each screwdriver. Four subjects started with the set of four ergonomical screwdrivers and used the control set of four screwdrivers later. The other four subjects began with the control set, followed by the ergonomical set.

FIGURE 17.3 A picture of the situation during the test.

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FIGURE 17.4 The drawing used to evaluate local postural discomfort. Four times during the test the subjects had to report their discomfort in the different regions A through P, using a scale from 0 to 5 (0 = no problems at all; 1 = very little discomfort; 2 = some discomfort; 3 = much discomfort; 4 = a lot of discomfort; 5 = maximal discomfort).

17.2.1

HEALTH

AND

DISCOMFORT MEASUREMENTS

For every subject the test started by experiencing the local perceived discomfort (LPD) scale. Subjects were asked to rate their postural discomfort in one of the regions (Fig. 17.4) shown on a diagram of the rear view of the arm, using a scale ranging from 1 (no discomfort) to 5 (extreme discomfort) modified after Corlett and Bishop (1976) and Borg (1982). First, the subjects learned the LPD scale. For every region they had to rate their experienced discomfort every 30 seconds by holding a 5 kg weight with arms horizontal anterior to the body until they were unable to hold the weight. After a rest period the test started, but before each test an LPD form was completed (pretest). The form was also completed four times during the test. The subjects were asked to fasten six screws as fast as possible, followed by completion of the LPD form and a break of 1 minute. The pretest value was subtracted from the other four measurement values and the result was taken as the LPD value. The same procedure was performed using the other screwdriver after a break of 45 minutes. In addition to LPD, postures were recorded by making lateral photographs with a camera from a fixed location. After the test, the subjects’ hands were evaluated for redness and blisters, and questions were asked about experienced friction, pressure points, and feelings of cramp. Before all tests the moment was measured by a special device. Subjects had to put the screwdrivers into the device and were asked to exert maximum force on a

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placebo screw mounted on a force measurement device. The same measurement was repeated for the other set of screwdrivers.

17.2.2

PRODUCTIVITY MEASUREMENTS

Productivity was recorded by measuring the time it took to fasten the 24 screws. Quality was measured by counting the number of incompletely fastened screws or screws that were not screwed straight into the drilled hole.

17.2.3

END- USER OPINION

After all experiments were done, the subjects completed a questionnaire on health, perceived productivity, quality, and the characteristics of the screwdriver sets.

17.2.4

STATISTICS

When possible, all of the differences previously discussed were tested with the ttest for paired comparison (p < 0.05).

17.3 RESULTS An overview of the differences between the two sets of screwdrivers is shown in Table 17.2.

TABLE 17.2 Results on Differences between Both Screwdrivers Ergonomical set LPD in % of the maximal difference between last measurement and pretest, averaged over 8 subjects • total • hand • lower arm Productivity • average duration of the task (sec.) • number of wrong screws Maximal force in % of the reference (averaged over 8 subjects) Experience of users: • experienced comfort • yes, I would choose this screwdriver • average score (1 = worse, 10 = superb) *

Control

55% (sd = 23) 30% (sd = 16)* 31% (sd = 22)

61%(sd = 25) 45%(sd = 21) 18%(sd = 22)

829 (sd = 88)* 6

983 (sd = 177) 33

140% (sd = 11)*

8 yes* 7 yes* 7.6 (sd = 1.0)*

significant difference (t-test for paired comparison, p < 0.05).

reference

0 yes 1 yes 6.3 (sd = 1.2)

Comfort Effects of Participatory Design of Screwdrivers

17.3.1

HEALTH

AND

213

DISCOMFORT

The differences in discomfort appeared to be very small. The differences were shown best by subtracting the first of the four LPD measurements from the last LPD measurement. The total score (the sum of all regions) was lower for the ergonomical screwdrivers, but not significant. Also, in the lower-arm region the differences were not significant. In the hand, the local experienced discomfort was significantly lower working with the ergonomical set. Inspection of the hands showed differences between both sets. After working with the control set, three subjects were found to have blisters that were not observed after working with the ergonomical set. Four subjects reported that they expected to have blisters after working with the control set. All subjects had problems with the high level of friction during the test, both for the ergonomical as well as for the control set. Four subjects complained about pressure on the ball of the thumb while working with the control set, and two subjects complained about this pressure with both sets. Working with the control set, two subjects experienced feelings of cramp, whereas no one experienced this working with the ergonomical set. Also, two subjects experienced irritating friction with the control set, but no one experienced this with the ergonomical set. The average maximum force with the ergonomical screwdrivers was 40% higher than the force that was measured with the control screwdriver. This could be caused by the fact that the diameter averaged over the four grips was 1.18 times larger with the ergonomical screwdriver compared to the control. However, if we correct for this difference in diameter the average maximum force is still 34% higher.

17.3.2

PRODUCTIVITY

The average screw time was significantly lower with the ergonomical set than with the control set. The reduction in screwing time was 16%, and the number of errors was also lower. Working with the control set resulted in thirty-three sloping screws or partly fixed screws, whereas using the ergonomical set resulted in only six errors (Table 17.2).

17.3.3

END- USER OPINION

The users’ preferences are presented in Table 17.3. Most of the users prefer the ergonomical set in regard to faster work, force exertion, balance, and grip on the handle and screw. The experienced comfort rating is better for the ergonomical set, as well as the average score (Table 17.2). After this research, one subject chose the control. His motivation was that the same brand of hand tool is used often in his sector.

17.4 DISCUSSION If we assume that the parameters of this study are good indicators for health, productivity, and comfort, the hypothesis that investment in ergonomics has no effect on health, productivity, and comfort in using a hand tool is falsified. In this section

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TABLE 17.3 Preferences Given after the Test by the Eight End Users, Regarding the Topics Described in the Left Column Preference for • faster working • force exertion • good grip on handle • good grip on the screw • good grip with oil on the grip

Ergonomical set 6 6 7 5 5

No difference 2 2 1 3 3

Control 0 0 0 0 0

the effects on health, productivity, and comfort are discussed per subject, followed by general remarks.

17.4.1

HEALTH

The indicators for health are local experienced discomfort and blisters. Previous studies (Grinten 1991) demonstrated that the variables constructed provide reliable results for comparison of conditions, such as in this study. Furthermore, for groups of subjects, reasonably linear relationships were found between load in the body and discomfort in a body region (Boussena et al. 1982), as well as between discomfort and holding time (Manenica 1986). Also, increased heart rates are observed with high discomfort values (Bystrom 1991). This strengthens our assumption that LPD is related to health. The LPD in the hand is lower with the ergonomical set, which could therefore be more healthful to use. The combination of pressure and local friction, which stretches the skin three to seven milimeters and also chafes the skin (Hall 1995; Bullinger and Solf 1979), is hazardous for the skin because it could result in blisters. The ergonomical set probably has lower values for pressure, friction, and chafing, which reduces the chance of blisters. The force level needed to insert the screw is lower with the ergonomical set, partly because of the diameter of the handle, partly because of a better fit in the hand, and partly because of the material used to make the screwdriver. This is in alignment with the fact that the chance of blisters is lower with the ergonomical set. However, some care should be taken regarding the conclusion that the ergonomical set is more healthful. First, for both screwdriver sets the experienced friction is high; second, a reduction in discomfort is shown in the hand region, but there is no reduction seen in total discomfort. Also, the test situation was tougher than actual working situations in order to increase the chance of showing differences. It could take a long time for these differences to be found in a real work environment, also in part because pneumatic or electric tools could be used for some screwdriving tasks. Furthermore, only short-term health effects are studied in this experiment, although long-term effects should be studied as well. Generalizing the results should also be done with care, because only eight young male subjects accustomed to screwdriving were studied. The effects on older persons

Comfort Effects of Participatory Design of Screwdrivers

215

or persons not used to screwdriving could be larger. Nevertheless, objective as well as subjective data indicate all trend in the same direction, which allows a conclusion (as this study indicates) that the ergonomical set is better from a health point of view.

17.4.2

PRODUCTIVITY

Objective as well as subjective data indicate a productivity increase with the new ergonomical set. In other words, the time needed to complete a specific screwing task is reduced using the ergonomical set. Also, the users found that the ergonomical set works faster. Not only is the task performed faster, but the quality is also better (fewer errors), which means that less repair time is required. It is to be expected that under real working conditions this productivity increase of 16% would also be found. That value will probably be lower because the intensive screwdriving performed in the test will rarely be found during real work, but in reality errors should be repaired quickly as well.

17.4.3

COMFORT

According to Helander and Zhang (1997), discomfort and comfort are different entities. Discomfort is more related to physical exposures, and comfort is more influenced by other factors such history and emotions. Comfort is very subjective, and the best way to measure comfort is by questioning. Parameters influencing comfort positively — such as faster work, lower force exertion, and a better grip on the handle and screw — are evaluated positively. Based on these data, it could be assumed that all subjects would buy the ergonomical set, after the test one subject still favors the control set. This shows how many factors influence a person’s preference.

17.4.4

GENERAL OBSERVATIONS

As discussed earlier, extrapolation of these results to real working situations is difficult, because the test conditions were extreme and the subjects were a select group. However, standardizing the test conditions and increasing the loading on the human body was needed in order to ensure that differences were found. It is plausible that in the long run some of the effects found in this study would still be seen under real working conditions. Of course this study could not demonstrate that the specific 11-step ergonomical design program mentioned in Section 17.1 caused the better performance of the ergonomical set. The important parts of the development process cannot be shown either. Therefore, this study only indicates that finding some way to emphasize ergonomics and the participation of end users is important to improve health, productivity, and comfort of workers using the end product. Ergonomics is important because this discipline focuses on adapting products to the behavior of humans using them. User participation is needed in product development because users are the only ones who can evaluate comfort during normal use of a product. To anticipate on that user participation is the only possibility.

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17.5 CONCLUSIONS Investments in ergonomics and user participation in product design can result in more healthful, productive, and comfortable products. In this chapter the effects can be shown objectively using an ergonomically designed screwdriver in a specific test situation, with specific subjects. However, health and comfort are very difficult to study objectively. In this study, only the effects on specific aspects of health (discomfort in the hand and blisters) could be shown. Long-term health effects should be studied further. The effects on several aspects influencing increase in comfort are also shown, but the comfort aspects studied are probably not strong enough to affect sales of the product. The importance of gaining more knowledge regarding comfort and hand tools is emphasized.

ACKNOWLEDGMENT The authors would like to thank Bahco Tools BV for providing the hand tools used in this study.

REFERENCES Arisz, H. and Kanis, H. (1999) “Towards concurrent monitoring of the number of subjects in user trials.” In M.A. Hanson, E.J. Lovesey and S.A. Robertson, eds., Contemporary Ergonomics, 50th Annual Conference of the Ergonomics Society, London: Taylor & Francis, 417–421. Bobjer, O. and Jansson, C. (1997) “A research approach to the design of ergonomic hand tools. The 11-point programme.” P. Seppälä, T. Luopajärvi, C.H. Nygård and M. Mattila, eds., From Experience to Innovation. Proceedings of the 13th Triennial Congress of the International Ergonomics Association, Helsinki: Finnish Institute of Occupational Health, Vol. 2, 193–195. Borg, G. (1982) “Psychophysical bases of perceived exertion.” Medicine and Science in Sports and Exercise, 14(5): 377–381. Boussena, M., Corlett, E.N. and Pheasant, S.T. (1982). “The relation between discomfort and postural loading at the joints.” Ergonomics, 25: 315–322. Bullinger, H.J. and Solf, J.J. (1997) Ergonomische Arbeitsgestaltung II Hand gefurthe werkzeuge Fallstudien, Dortmund: BAU (Forschungsbericht nr 197). Byström, S. (1991) Physiological Response and Acceptability of Isometric Handgrip Contractions, Solna: Arbetsmiljöinstitutet (Arbete och Hälsa). Chao, A., Kumar, A.J., Emery, C.T.N.D., Nagarajarao, K. and You, H. (2000) “An ergonomic evaluation of cleco pliers.” In Proceedings of the 14th Triennial Congress of the International Ergonomics Association, San Diego: 4-601 (on CD-ROM). Corlett, E.N. and Bishop, R.N. (1976) “A technique for assessing postural discomfort.” Ergonomics, 19: 175–182. Fellows, G.L. and Freivalds, A. (1991) “Ergonomics evaluation of a foam rubber grip for tool handles.” Applied Ergonomics, 22(4): 225–230. Grinten, M.P. van der (1991) “Test-retest reliability of a practical method for measuring body part discomfort.” In S. Kumar, ed., Advances in Industrial Ergonomics and Safety IV: 311–318.

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Hall, C. (1995) Hand Function with Special Regard to Work with Tools, Stockholm: NIOH (Arbete Och Hälsa 4). Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.” Ergonomics, 40: 895–915. Manenica, I. (1986) “A technique for postural load assessment.” In E.N. Corlett, I. Mananica, and J.R. Wilson, eds., The Ergonomics of Working Postures, London: Taylor & Francis, 270–277. McGorry, M. (2001) “A system for the measurement of grip forces and applied moments during hand tool use.” Applied Ergonomics, 32: 271–279. Mital, A. (1991) “Hand tools: Injuries, illness, design and usage.” In A. Mital and W. Karwowski, eds., Workspace, Equipment and Tool Design, Amsterdam: Elsevier, 219–256. Polling, D. (1999) Ergonomics in the Product Design Process, Hoofddorp: TNO (in Dutch). Thackara, J. (1997) Winners! How Today’s Successful Companies Innovate by Design, Amsterdam: BIS. Vink, P. and Koningsveld, E.A.P. (2000) “Impressions of the IEA2000 congress.” Nederland Tijdschrift voor Ergonomie, 25(50): 146–148 (in Dutch).

Manual Bag 18 Comfortable Sealing M.D. Hagedoorn-de Groot, T. Bosch, S.M. Eikhout, and P. Vink CONTENTS 18.1 18.2 18.3 18.4 18.5

Manual Bag Sealing...................................................................................219 Development...............................................................................................220 User Research.............................................................................................220 Methods ......................................................................................................220 Results ........................................................................................................223 18.5.1 Sealing by Shop Assistants..........................................................223 18.5.2 Opening by Consumers ...............................................................223 18.5.3 Safety ...........................................................................................225 18.5.4 Overall Score ...............................................................................225 18.6 Conclusions ................................................................................................228 Acknowledgment ...................................................................................................228 References..............................................................................................................228

18.1

MANUAL BAG SEALING

Customers continually expect faster, more efficient, and more thorough service at supermarkets (Carrasco et al. 1995), but also in other shops where bags are sealed. Manual bag sealing is often used in shops where products are sold that have to be protected for hygienic reasons (meat or bread) or to bundle several smaller products (candy). A variety of seals are used to close these bags. Shop assistants use seals mainly to close the plastic bags which the consumer opens at home and often seals again. For shop assistants, sealing the bags is a repetitive, physically demanding action that takes some time and could cause discomfort because of the physical load in combination with the time pressure. Several studies show the negative effects of highly frequent movements in combination with force exerted in poor working postures (Bongers, 2003; Macfarlane et al. 2000). Opening and closing the bags again can cause some discomfort or annoyance for consumers also, in the event they cannot open the bag or when the seal is not closing the bag well enough. This activity can create a safety hazard as well because children could swallow the sealing devices. 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

219

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18.2 DEVELOPMENT Several systems are available for sealing plastic bags, but both consumers and shop assistants mention that most of them have disadvantages. Some could be hazardous, for example, if children swallow the bag sealing devices. Some are made with adhesive tape, which could be difficult to open, and some take a lot of time to wrap around the plastic bag. Knowing these potential shortcomings, Twin Seal developed a new system of sealing. Various ideas and prototypes resulted in a system with an adhesive tape that has a piece of paper at each end to keep them from sticking together. The idea is that shop assistants could save time, because a special machine fastens the seals. Consumers could experience more comfort in easily opening the bag, and it should be safer because it is more difficult for children to swallow it.

18.3 USER RESEARCH An evaluation was set up to study whether the assumed improvements are also experienced by end users. A comparative test of the discomfort, safety, and efficiency of four different types of plastic bag seals was performed. This test was performed by both shop assistants (for sealing) and consumers (for opening and sealing again). The tested seals are a) a paper- or plastic-covered iron wire; b) a metal clip; c) standard adhesive tape; and d) the new adhesive tape with a piece of paper at each end (Fig. 18.1). Systems (c) and (d) are always used in combination with a tape machine (Fig. 18.2), so, these two sealing devices are tested using the tape machines. The research questions are 1. 2. 3. 4.

Which system do shop assistants prefer? Which system do consumers prefer? How do the different kinds of systems score on safety? What is the final evaluation?

18.4 METHODS Twenty shop assistants (age 16 to 50 years old, average age 31.5 years), twentyfour consumers (age 8 to 85 years old, average age 40.3 years) and five experts on ergonomics and safety participated in the study. The shop assistants evaluated the sealing of the bags, the consumers evaluated the opening and sealing, and the experts evaluated the safety and also the user friendliness and physical load. The shop assistants are employees of the bread and meat products department who have to seal many bags daily. Three groups of consumers were selected: eight youngsters (age 8 to 19 years, average age 13 years), eight adults (age 26 to 51 years, average 34.4 years) and eight seniors (age 57 to 85 years, average age 73.4 years). Every participant evaluated

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FIGURE 18.1 The four different seals compared in this test: (A) a paper- or plastic- covered iron wire; (B) a metal clip; (C) adhesive tape; and (D) the new adhesive tape with a piece of paper at the ends.

the four sealing systems. To answer the four research questions, the study consisted of four activities: 1. During the sealing done by the shop assistants the sealing time was measured while sealing five bags, one after the other. The time started the moment the first bag was picked up and ended when the fifth bag was laid down. The average time for every seal was measured and tested with a t-test for paired comparison (p < 0.05). Video recordings were made, and the experts evaluated these recordings. After using all systems, every

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Comfort and Design: Principles and Good Practice

FIGURE 18.2 Example of a tape machine often used to seal bags with adhesive tape.

participant was asked to complete a questionnaire with questions about efficiency, safety, and the experienced comfort and discomfort. 2. The opening of the bags was tested by twenty-four consumers. The consumers were selected at sports fields (youngsters), among families and friends (middle age), and in a residence for the elderly (seniors). The subjects were informed that TNO, an independent research organization, would like to know which of the four sealing systems is preferable. After opening five bags with each type of sealing system, every participant was interviewed with questions regarding discomfort, physical load, and user friendliness. Some subjects were also recorded on tape, the recordings to be used in the expert session. The video recordings were used in the expert session for further analysis. The experts also sealed bags using the four systems. Their opinions on safety, physical load, and productivity were based on the video and their own experience. The expert panel consisted of five members (two industrial designers, a movement scientist, an ergonomics expert, and a product safety expert). 3. The issue of safety was studied based on the observations and video recordings, as well as in discussions by the expert panel. Also, additional information was gathered by mind-mapping on what and who could be found in the neighborhood of the bag sealing products. In the questionnaires for the consumers and shop assistants, the subjects had to give a safety rating for each system. 4. For the food industry, a total evaluation could help to show which system is best. Therefore, all consumers and shop assistants were asked which element is most important: safety, user friendliness, quality, or work pace. The expert panel made a total judgement over all systems, having all the data available. All separate evaluations and a total expert judgment were

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combined in a table (see Table 18.1 in Section 18.5.4) rating the systems as very good, good, neutral, bad, or very bad.

18.5 RESULTS 18.5.1

SEALING

BY

SHOP ASSISTANTS

Regarding comfort, the average score of the shop assistants was higher for the usual adhesive tape and the adhesive tape with paper than for the other two systems. The majority of the shop assistants called the ordinary adhesive tape and the adhesive tape with paper very easy to use, whereas the plastic-covered wire and the clip were rated difficult or very difficult to use (Fig. 18.3). The physical workload estimated by the experts based on the video recording is lowest for the tape-and-paper system and the traditional tape system. The traditional tape system is somewhat better, because less force is needed to push the bag downward. Both other systems (wire and clip) have a higher physical load, because various repetitive handlings are needed. The recorded sealing times for the adhesive tape and the adhesive tape with paper were significantly lower (Fig. 18.4; t-test paired comparison, p < 0.05) than for the other two systems.

18.5.2

OPENING

BY

CONSUMERS

Fair and good ratings in regard to opening the fastener were given for the paper- or plastic-covered iron wire and for the metal clip by all ages of consumers (Fig. 18.5).

100%

80%

60%

40%

20%

0% plastic

metal fair/good comfort

tape

tape+paper

fair/good use

FIGURE 18.3 Percentage of the twenty shop assistants rating the comfort and use of the four bag-sealing systems fair or good, using a five-item scale (bad, moderate, neutral, fair, good).

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sealing time (s) 10

8

6

4

2

0 plastic

metal

tape

tape + paper

FIGURE 18.4 The recorded sealing time for the four types of sealing systems, averaged over twenty shop assistants, each sealing five bags (100 recordings per tape).

The youngsters and middle-aged consumers also rate the adhesive tape with a piece of paper in between fair or good. Not all groups appreciate the use of the adhesive tape system in opening bags. Regarding comfort, a comparable result was found (Fig. 18.5). Fair and good comfort ratings for opening were recorded by all ages for the paper- or plastic-covered 100

fair/good use (%)

80

60

youngsters middle aged elderly

40

20

0 plastic

metal

tape

tape+paper

FIGURE 18.5 The opinion of consumers on the opening of plastic bags sealed with the four systems, given as the percentage of consumers (youngsters, middle-aged, elderly) rating each of the four systems fair or good.

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iron wire and for the metal clip. The youngsters and middle-aged consumers also rated the adhesive tape with a piece of paper in between fair or good. The comfort rating by all groups for the adhesive tape system was low or neutral when opening bags. The seniors rated the comfort level relatively low for all systems. When we asked the preferences of the groups, the seniors preferred the metal clip (56%) (although the seniors did not experience any seal as comfortable). The adults did appreciate the adhesive tape with paper (50%), and the youngsters preferred the adhesive tape with paper as well (46%). The seniors mentioned problems with opening the adhesive tape with paper, because this action requires muscle strength and fine coordination.

18.5.3

SAFETY

The experts’ opinion is that safety is an important item, and they mentioned the risks of using the different seals. One of these risks is that a loose plastic-covered iron wire, or a clip, could fall or slide into an area where children could find it. A child could put it into the mouth and swallow it. The experts also mentioned the danger that a small part of the clip might break off and could also be swallowed. For both the ordinary adhesive tape and the adhesive tape with paper, the swallowing risk is smaller. Other risks that were mentioned by the experts are that one could possibly be pricked or cut by the sharp edges of the plastic-covered wire, or the clip. Shop assistants can hurt their hands at the sides of the machines that apply the adhesive tape seal. This is confirmed by shop assistants, who say that they sometimes cut their fingers on the metal clip or are pricked by the plastic-covered wire. Six out of nine shop assistants who regularly worked with the metal clip mentioned cutting injuries to the fingers, and two mentioned the hand. Two out the thirteen shop assistants who worked regularly with tape mentioned hand injuries, and one mentioned finger injuries. Both the expert panel and the consumers mentioned the possibility of getting injured by the use of a knife, fork, or scissors to open both kinds of adhesive tape seals. This risk is higher when using the adhesive tape without paper, because the chance that a consumer will use a scissor or knife to open that type of seal is higher. Figure 18.6 presents the total safety score for the four seals that was given by the shop assistants and the consumers. The adhesive tape seal with paper was evaluated as the safest by the expert panel. This rating is somewhat different from that given by users. Figure 18.6 shows the total score for safety of the four seal systems given by the shop assistants and consumers. In fact, all systems are evaluated safe enough. Figure 18.8 shows shots of the video recordings that were used in the expert session.

18.5.4

OVERALL SCORE

Most of the shop assistants (59.3%) prefer adhesive tape with paper (Fig. 18.7). Looking at the consumers’ results, the preference is less evident. Their preferences differ and show an equal division. Approximately 30% prefer the plastic-covered

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10 9 8 7 rating

6

shop assistants

5 consumers

4 3 2 1 0

al et

tic

as pl

m

pe ta

r pe a +p pe ta

FIGURE 18.6 Ratings given by the twenty-four consumers and twenty shop assistants regarding the safety of the different systems (0 = unsafe, 10 = extremely safe).

iron wire, the clip, or the adhesive tape with paper (34.6%, 30.8%, and 30.8%, respectively). If a division is made between the three ages, it is clear that the elderly prefer the metal clip and the young and middle-aged groups prefer the tape with paper, followed by the plastic-covered iron wire.

70

% that chooses the system

60 50 shop assistants 40

young cons. middle cons.

30

old cons. 20 10 0 plastic

metal

tape

tape+paper

FIGURE 18.7 Percentage of the consumers and shop assistants who preferred one or another of the sealing systems. The total is higher than 100%, because almost half of the subjects mentioned two preferences.

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FIGURE 18.8 Screen shots from the video recordings used by the expert panel: (A) plasticcovered iron wire is used to seal a bag; (B) an older woman is reclosing the bag with plastic covered iron; (C) middle aged man is opening a bag with adhesive tape.

Table 18.1 summarizes the judgments of the shop assistants, the consumers, and the expert panel. The table with the total score has some arbitrary elements, but the expert panel agreed on the scores. Because of positive ratings for safety, physical load, comfort in use, and the high speed mentioned by shop assistants, the tape-and-paper system was evaluated as the best, which means that the development of this system was successful.

TABLE 18.1 Summary of the Scores for the Four Sealing Systems Shop assistant Speed Plastic-covered wire Metal clip Tape Tape with paper

− − ++ ++

Safety

+/− − ++ ++

Consumer

Comfort and use − − + +

Speed

Comfort and use

+ + −− +/−

++ (very good); + (good); = (neutral); − (bad); − − (very bad)

+ + −− +/−

Expert Physical Safety load −− − ++ +

− − − +

Total score

− − +/− ++

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18.6 CONCLUSIONS Improvement of a simple activity such as sealing a bag could play a role in the prevention of musculoskeletal injuries or some other type of hazardous situation. The new system was developed and rated positive in regard to comfort by most of the end users, and it can certainly be seen as an improvement. This new system should be promoted, but further instruction to end users is needed regarding safety. If possible, innovations should be found to make unsealing easy for everyone, including the elderly. The following conclusions can be drawn from this study: •

•

•

•

•

For sealing plastic bags, the adhesive tape with paper is the best of the four systems, closely followed by the plain adhesive tape. Both seals score well as far as speed and safety are concerned. These two seals are also the best in regard to comfort. Consumers prefer the system of the adhesive tape with paper and it is evaluated safer by the experts. The physical load involved in sealing with adhesive tape is evaluated more positively than in sealing with adhesive tape with paper. Consumers think that the plastic-covered iron wire and the clip open fastest, and they think these are the easiest ones to use. The consumers prefer the plastic-covered iron wire, clip, and adhesive tape with paper to the plain adhesive tape. The young and middle-aged prefer the adhesive tape with paper. For seniors, there is no seal available that is easy and comfortable to use, in their opinion. Safety is rated higher in sealing with adhesive tape with paper. According to the shop assistants, sealing bags with both systems using adhesive tape is the easiest and fastest. However, the consumers mention that the seal without paper is the most difficult to open. They also mention the difficulty of resealing bags that have been opened. In short, there is still no seal that is experienced to be comfortable by all shop assistants and all consumers. If we had to recommend a seal it would be the seal using adhesive tape with paper, because sealing plastic bags is a daily recurring, intensive activity for shop assistants.

ACKNOWLEDGMENT The authors want to thank Twin Seal for their support in this research.

REFERENCES Bongers, P.M. (2003) Make Work to Prevent RSI, Amsterdam: Vrije Universiteit (inaugural address). Carrasco, C., Coleman, N. and Healey, S. (1995) “Packing products for customers.” Applied Ergonomics, 26(2): 101–109. Macfarlane, G.J., Hunt, I.M. and Silman, A.J. (2000) “Role of mechanical and psychosocial factors in the onset of forearm pain: Prospective population base study.” British Medical Journal, 321: 676–679.

View 19 Comfortable in an Earth-Moving Machine of 2015 L. Vormer, M.C. Dekker, A.A. Visser, F. Krause, and P. Vink CONTENTS 19.1 19.2 19.3 19.4

Introduction ..................................................................................................229 Current Situation ..........................................................................................230 Improvement Possibilities for View.............................................................230 Demands from the Literature.......................................................................230 19.4.1 Direct View.......................................................................................231 19.4.2 Indirect View ....................................................................................232 19.5 Information from Operators and Manufacturers .........................................232 19.6 The Design Approach ..................................................................................234 19.7 The Three Concepts .....................................................................................235 19.8 The Future Machine.................................................................................... 236 19.9 Conclusions ..................................................................................................237 References..............................................................................................................237

19.1 INTRODUCTION The operator’s comfort is increasingly recognized as a factor of importance in selling earth-moving machines (Krause et al. 2003). From 2001 to 2003 a Eurocabin project was carried out for three medium-sized earth-moving machine manufacturers: Paus GmbH (Germany), coordinator of the project; ETEC (the Netherlands), and Kaiser (Liechtenstein). A part of this project, which describes the design of the excavator of the future, concerns improvement of the operator’s view. The highlights of this study are presented in this chapter.

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FIGURE 19.1 Example of an old excavator cab.

19.2

CURRENT SITUATION

Operator comfort in earth-moving machines has improved drastically the last four years (Chapter 2). An old excavator cab, such as the one shown in Fig. 19.1, is seldom seen nowadays. However, improvement possibilities can still be found in the new machines. The most frequently mentioned improvement possibilities in new machines (less then 4 years old) involve the seat and vibration. In excavators, 22% of the drivers also mention the need for improvement of the operator’s view (Kuijt-Evers et al. 2003). This chapter is concerned with that view, an aspect of interest to both manufacturers and operators. View is not only related to comfort, but also — perhaps even more importantly — to quality and productivity. A good operator’s view of the direct working area reduces the chance of extra corrections or mistakes.

19.3

IMPROVEMENT POSSIBILITIES FOR VIEW

In this project, a study of the operators’ existing view was carried out. Literature was studied; operators, manufacturers, and experts were interviewed; and the view from existing excavator cabins was analyzed.

19.4

DEMANDS FROM THE LITERATURE

Reviewing the literature, a paper by Roetting (2003) that presents an overview of the subject of view appeared to be important. Roetting divides the concept into two parts: direct view and indirect view.

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19.4.1

231

DIRECT VIEW

Different methods are in use and/or proposed to identify blind spots in the field of view of an operator (Giguère and Lame 1996). Most of them calculate the visibility for an average person (e.g., 50th percentile male) and assume only a static posture for the operator. Although this makes it easier to compare different vehicles or to quantify changes made to a vehicle, it is a gross simplification. Operators of varying heights will operate a wheel loader, and they can (and will) change their head and body positions dynamically. See Land and Horwood (1996) for a study of the relation of head and eye movements to driving). Demands for a direct view from a wheel loader cabin can be summarized as follows:

•

•

•

• •

The windows should allow viewing of as much of the surrounding environment as possible. Table 19.1 gives an indication of the relative importance of the different areas to different tasks. The windows should be as low as possible to allow viewing of the immediate surroundings. The number of occlusions (e.g., parts of the cabin frame, the bucket, the bucket arm, mirrors, and displays and other elements within the cabin) should be minimized. If occlusions cannot be prevented, their size should be minimized. All windows that are essential to the outside view should be equipped with windshield washers and wipers. The wipers’ field of coverage should be maximized. Reflections from inside the cabin should be minimized. Blinding by the sun should be prevented by a blind or a window coating. Fogging of the windows should be prevented by heated windows and adequate ventilation; distortions due to curvatures of the windows should be minimized.

TABLE 19.1 Weight Factors for Different Aspects of the Outside View Transport Transport with loading/unloading Loading/unloading with transport Loading/unloading with transport moving forward and backward Loading/unloading or handling/processing without transport From Roetting (2003) after Vedder (1997).

Front view 0.8 0.6 0.4 0.3 0.2

Work area view 0.2 0.4 0.4

Rear view 0.2 0.2 0.2 0.3

0.7

0.1

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19.4.2

INDIRECT VIEW

Indirect vision systems serve two purposes. They reduce the time needed to view areas behind the vehicle, for example, by moving parts of the rear view into the front view field (Flannagan and Sivak 1993). They also give access to information necessary for safe task execution in areas that are not directly viewable, the so-called blind spots. Indirect view can be achieved by means of mirrors or cameras or by other (technical) means (e.g., collision avoidance systems). There is always a trade-off between the area made visible by the indirect view system and the occlusion of information in the forward visual field. Demands for indirect viewing by wheel loader operators can be summarized as follows: • • • •

•

Provide indirect view systems to minimize the number of blind spots. Do not occlude important areas of information with indirect view systems. All indirect view systems should be easily adjustable to different operators and different operating conditions (e.g., servo-adjustable mirrors). All indirect view systems should be provided with means to ensure their function even during adverse environmental conditions (e.g., heated mirrors to prevent fogging). Indirect view systems should be evaluated under working conditions (e.g., vibrations can reduce the usefulness of indirect view systems).

19.5

INFORMATION FROM OPERATORS AND MANUFACTURERS

The interviews with operators and manufacturers also generated some valuable information. It appeared that the operator’s view of the direct working area could be restricted by the cabin frame, dashboard, or the undercarriage (Fig. 19.2). The hydraulic arm could restrict the view (Fig. 19.3), and visibility around the machine is restricted by the machine itself. There is little visibility to the vehicle’s right and rear, but this view could be important in maneuvering backward and rotating the upper carriage. Other problems that came out of the interviews related to the view are sunlight, dust, window damaging and deformation of visibility: 1. Sunlight. A solution increasing the view could be to increase the window surface. However, a larger screen surface means more sunlight, which can be troublesome, especially on summer days. Currently, sunlight is already seen as a problem. 2. Dust. Dust reduces visibility, so a larger window surface implies that a larger area has to be cleared of dust. 3. Damage. More window area means more possibilities for vandalism and falling objects to damage the window. In the interviews, subjects mentioned that vandals sometimes damage vehicle windows. 4. Deformation. Sometimes curved windows are used to enlarge the viewing area. From a styling point of view, this also offers also interesting form possibilities (Figure 19.4). According to the operators, however, looking through curved windows deforms the image and could even result in

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FIGURE 19.2 The work area that can be seen by the operator (gray = areas with restricted visibility).

FIGURE 19.3 The hydraulic arm could restrict the view.

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FIGURE 19.4 An O&K machine with very nice styling made possible by curved glass. (A) is a closeup of the cab; (B) is an overview of the complete machine. (Photo courtesy of O&K.)

headache or tired eyes. It is best to look through window glass that is perpendicular to the viewing axis. These are only a few of the problems related to view that make finding a solution very difficult.

19.6 THE DESIGN APPROACH Based on the defined problems, including the related problems mentioned above, improvements were developed by a design team. It started with ideas that were formulated based on discussions with operators and manufacturers. The ideas were again shown to operators and the discussions led to three concepts that were

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FIGURE 19.5 Concept longneck.

developed further. The three concepts were presented and discussed with operators, manufacturers and experts in the field of comfort and design. All of this was input for the final design of the Machine of 2015.

19.7

THE THREE CONCEPTS

In this chapter the three designed concepts are called longneck, rocking chair, and solist. A characteristic of the longneck concept (Fig. 19.5) is that the operator always looks through a flat window and the work area is seen without deformation. The moving cabin allows repositioning in order to achieve the best position for a good view. The rocking chair concept (Fig. 19.6) has a saddle seat, which enables the

FIGURE 19.6 Concept rocking chair. (A) shows the in- and egress situation; (B) shows different positions of the chair that increase view and variation in posture.

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FIGURE 19.7 Concept solist. (A) is working with the remote control enabling optimal view; (B) is driving to the ideal position to see the working area.

operator to sit like a motorcyclist and look downward. A window in the floor is covered by a plate that can be opened so the operator can look downward. A sliding door makes it possible to increase the view to the left and also improves the ventilation possibilities, because now the door can be opened and fixed in different positions. The solist concept (Fig. 19.7) has a movable cabin that can be separated from the machine, and the machine can be operated by remote control. The operator can then choose the ideal position for looking at the working area.

19.8 THE FUTURE MACHINE In evaluating the three design concepts, both disadvantages and advantages were mentioned by the operators, manufacturers, experts, and designers. These were all listed and became the input for the final design of an excavator for 2015. This final design (Fig. 19.8) has a moving cabin that can be elevated to look over obstacles or the hydraulic arm. It can also be tilted forward and backward to optimize the view through the flat window. A sliding floor panel can be uncovered to reveal a window underneath, enabling a direct downward view. Almost all grey areas in Fig. 19.2 now become white, which is a significant (almost 100%) improvement of the view. When working overhead the cabin can be elevated (Fig. 19.8A), and in working under the machine the cabin can

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FIGURE 19.8 The excavator of 2015, featuring a better view with the hydraulic arm raised (A) and lowered (B).

be positioned forward and the sliding floor panel can be opened (Fig. 19.8B). A touch screen in the cabin allows the operator to view the area around the machine via cameras. Sensors warn of obstacles while the machine is moving. The windows are made of a special material that is almost unbreakable, with a special coating that cleans itself in rain, as many office building windows now do. Each part of the window can be made darker (to reflect sunshine) by changing an electrical current, and the operator can make this change himself.

19.9 CONCLUSIONS Innovations are still possible to increase the view, and thereby the comfort, of the earth-moving machine operator. There is a question as to whether this machine will be operating in 2015. However, the study has generated a large number of ideas that could be helpful in designing new machines in the short term, as well. Some of these ideas are implemented in today’s new machines, and a few ideas have been mentioned in this chapter to show that there are more possibilities for improving the operator’s view. A better view is important because it is a sales argument. A machine that enables more accurate work, increases productivity, and is safer and more comfortable is interesting to operators, management, and manufacturers alike.

REFERENCES Flannagan, M. and Sivak, M. “Indirect vision systems.” In B. Peacock and W. Karwowski, eds., Automotive Ergonomics, London: Taylor & Francis, 205–217. Giguère, D. and Larue, C. “The visibility audit: A conceptual framework for the assessment of visibility around trucks and industrial vehicles.” In A.G. Gale, I.D. Brown, C.M. Haslegrave and S.P. Taylor, eds., Vision in Vehicles V, Amsterdam: Elsevier, 371–378.

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Krause, F., Bronkhorst, R.E. and Looze, M.P. de, eds. (2003) Comfortable Earth-Moving Machinery, Hoofddorp: TNO. Kuijt-Evers, L.F.M., Krause F. and Vink P. (2003) Aspects to improve cabin comfort of wheel loaders and excavators according to operators.” Applied Ergonomics, 34(3): 265–272. Land, M. and Horwood J. “The relations between head and eye movements during driving.” In A.G. Gale, I.D. Brown, C.M. Haslegrave and S.P. Taylor, eds., Vision in Vehicles V, Amsterdam: Elsevier, 153–160. Roetting, M. (2003) “View.” In F. Krause, R.E. Bronkhorst and M.P. de Looze, eds., Comfortable Earth-Moving Machinery, Hoofddorp: TNO, 21–30. Vedder, J. (1997) Systematische Bewertung der ergonomischen Gestaltung ausgewahlter Nutzfahrzeuge, Düsseldorf: VDI-Verlag. Vink, P. and Hark. T. ter. (2003) “Future demands on comfort in construction vehicles’ interiors according to manufacturers.” In F. Krause, R.E. Bronkhorst and M.P. de Looze, eds., Comfortable Earth-Moving Machinery, Hoofddorp: TNO: 99–105.

20 Tram Drivers’ Comfort D.S.C. Osinga, P. Vink, and J.C. Becker CONTENTS 20.1 20.2 20.3

Tram Interior Requirements.......................................................................239 Requirements to Optimize Driver Performance ........................................240 The Design Process....................................................................................240 20.3.1 A Stepwise Participatory Approach ............................................240 20.3.1.1 Step 1: Test the First Design .....................................241 20.3.1.2 Step 2: Test the First Mock-Up .................................241 20.3.1.3 Step 3: Test the Improved Mock-Up and Emergency Handle ..............................................242 20.3.1.4 Step 4: Dynamic Test of Seats ..................................243 20.3.1.5 Step 5: Final Evaluation ............................................244 20.4 Results ........................................................................................................244 References..............................................................................................................245

20.1

TRAM INTERIOR REQUIREMENTS

The requirements placed on trams in regard to comfort, safety, and capacity are high-level and numerous at the same time. Trams should be comfortable and safe for passengers and should allow them to get in and out of the tram fast. Also, capacity should be enlarged due to the increasing number of passengers. Apart from the needs of passengers, the driver’s cab should meet the driver’s needs. The cab should be comfortable for small, tall, slender, and corpulent drivers, and should stimulate safe driving as well as good visibility and clearance. The public transport enterprise of Rotterdam RET (Rotterdamse Elektrische Tram) is confronted with these changing demands and therefore pays much attention to the process of designing new trams. First, the requirements for a new tram are defined, and after an invitation for European bidders, the company is chosen that will deliver the new trams. The supplier was Alstom (France). Their tram was chosen because it best fit the requirements, but also because adaptations were still possible. An important advantage was the high capacity. The Alstom is a relatively wide tram and has a low floor, which increases capacity and passenger comfort in getting in and out of the tram. Based on the

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239

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existing Alstom concept the RET specified the outside appearance and many technical features. Also, the interior was specified in cooperation with specialists in vehicle interior design from TNO. The process of the driver’s cab specification is the focus of this chapter.

20.2

REQUIREMENTS TO OPTIMIZE DRIVER PERFORMANCE

It is essential to adapt a driver’s cab to the principles of human behavior in order to enable optimal human performance. Nowadays, many software packages are available to support an ergonomical design. An ergonomical design is needed both to let drivers fit in the vehicle and to check sight lines and reach envelopes. These software packages are especially useful in the early stages of development. However, it is impossible to predict both human behavior and the feeling of comfort. Therefore, in a later stage of design the participation of various drivers will always be needed to test the cab’s handling, view, and comfort. This is essential because all drivers should have a good view of the traffic in front and to the left and right of the tram. An example of a RET requirement is that the driver should be able to see an object one meter high located at a distance of one meter from the tram. Also, real users should test the controls and displays, because they know the driver’s work best. Comfort is also an essential element for other reasons. First, comfort promotes a healthful environment so that drivers become less ill and are sooner able to work again. Another reason is that comfort can keep the driver more alert during the shift without being diverted or tired by discomfort. Finally, drivers are used to the high comfort standards in their cars or at home, and they expect that in the work station, too.

20.3 THE DESIGN PROCESS 20.3.1

A STEPWISE PARTICIPATORY APPROACH

Ultimately, the driver’s cab should be a workplace that enables optimal performance by the driver. Therefore, in the process of developing the new tram the driver played an important role. In this project a stepwise approach used in a train interior design process was used (Bronkhorst, et al. 2002). Explicit attention was given to the communication in the process between designers of Alstom, drivers of the RET and researchers of TNO (see also Chapter 4). We tried to make the drivers and designers owners of the solutions (Wilson 1995). The three groups met in each step of five successive steps. A project group guided this process. The project group consisted of a “manager tram” of the RET, a representative of the RET union, a number of drivers, an instructor from the drivers’ training department, and a specialist in work research. This project group guided the process of the optimal cab design through the five crucial steps. At a few points in the process the project group had to report their progress to a steering group, which arranged coordination with other project groups in regard to technology, exploitation, and the passenger interior of the new tram. During the process Alstom delivered a number of mock-ups to evaluate the design and to

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241

communicate about possible changes. TNO added an expert opinion and analyzed the tests done by the drivers, and then converted these data into redesign proposals. 20.3.1.1

Step 1: Test the First Design

In the first step designers of Alstom made drawings of the cab interior based on the requirements. These designs were discussed at the end of this step, and discussion of these drawings resulted in some changes. Climate control was hardly possible in the proposed interior because of the large dashboard. The dashboard was a large horizontal plane extending from close to the driver to the coachwork, making ventilation nearly impossible because the air flow is hindered. Also, and probably more important, sight lines drawn in the design showed that the driver’s sight was reduced because of the large dashboard. Smaller drivers were not able to have a good view of the traffic. The position of displays and controls could also be improved. 20.3.1.2

Step 2: Test the First Mock-Up

Based on the results of step 1 the project group decided to make a new design based on other designs that were available for this tram. The new design included modified controls and displays and a more rounded dashboard surface to enable a better view of traffic. Another adaptation was the addition of height-adjustable pedals (Fig. 20.1) next to the height-adjustable seats. Height-adjustable pedals are relatively new in trams. To enable good traffic sight for drivers of different heights, height-adjustable seats are often found in trams, and sometimes even height-adjustable dashboards. Height-adjustable pedals are not often found, but their advantage is that the driver’s sight lines relative to the dashboard and the coach-work can remain fixed, regardless of the anthropometrics of the individual drivers. This design was shown in a mock-up (Fig. 20.2) that was evaluated by eight

FIGURE 20.1 Height-adjustable pedals.

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FIGURE 20.2 The mock-up used in the test.

drivers in four sessions, using a protocol set up by TNO. Drivers with extreme body characteristics were used to test the adjustability. Tall and short drivers, as well as both slender and corpulent drivers, participated in the test. Three seats that were chosen based on previous tests (two new seats and one used in the current tram) were tested in the mock-up. The height adjustability of both seats and pedals were evaluated positively. Traffic close to the tram could be observed adequately during a simulation. All three seats were evaluated positively. Drivers mentioned during the test that a dynamic test is needed to choose a seat, because the vertical vibration is not always dampened effectively by the seat. It was decided to do a dynamic test in a comparable tram. New problems were also discovered during this test, for example, the problem of knee space. The knee space provided was theoretically (and in the software) adequate, but for real drivers the test showed that the knee space was too small. Based on the discussion of the test results it was decided to make the dashboard more U-shaped to create additional space in front of the driver. Another problem was the fact that for precision handling and steering a more adequate armrest was preferred. It was decided to add an adjustable arm support for the right arm and a fixed wrist support for the left hand (Fig. 20.3). 20.3.1.3

Step 3: Test the Improved Mock-Up and Emergency Handle

In the third step six drivers evaluated the U-shaped mock-up, and it was decided to choose this design. At this point further refinements were made, such as the positioning of the controls and displays, the instructor’s seat for the instructor tram, and a sun-blind. In this step the emergency brake was also tested. Alstom was able to deliver a new emergency brake integrated into the drive-stop handle (Fig. 20.4). In existing RET trams drivers have to press a pedal continuously, and taking the foot off this pedal causes an immediate stop. In the new tram the integrated handle requires

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243

FIGURE 20.3 The armrests supporting precise handling.

that the driver’s hand cannot leave the handle, because doing so causes the emergency stop. Drivers tested the new system in an existing tram. Based on this test, the old system was preferred by drivers as well as by the experts, because of the armload required by the new system. Therefore, the old system will be built into the new tram. 20.3.1.4

Step 4: Dynamic Test of Seats

The next step was the dynamic evaluation of three seats in an existing comparable tram. All three seats were tested by drivers according to a fixed protocol, and

FIGURE 20.4 The emergency stop feature integrated into the drive-stop handle.

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FIGURE 20.5 The prototype for examining all parts of the interior and exterior design.

objective tests were done regarding vibration and pressure distribution. Analysis of these tests showed that one of the seats was not appropriate for the tram in the Rotterdam area. This seat did not provide enough support in the lateral direction and did not dampen the vibration enough. One seat was rated best, but improvements were needed, such as adjustment of the armrests to give more support, a flatter front of the seat, and better pressure distribution characteristics. Other recommendations concerned technical aspects to improve stability and maintenance. The supplier was satisfied with the specific research-based comments and was willing to adapt the seat. 20.3.1.5

Step 5: Final Evaluation

In the last step a complete mock-up was evaluated, consisting of a part of the passenger cabin. Also, the chosen colors, light, and pictograms of displays were tested separately. The first prototype was again checked by drivers and management (Fig. 20.5). Some details were modified, but the total was evaluated positively.

20.4 RESULTS The active involvement of several drivers and the use of the research-based redesign approach ensure that all knowledge available in designers, drivers, and experts is used. New knowledge also became available in the course of doing the tests. It is expected that Alstom’s final tram interior will be optimally adapted to the needs of the drivers, because the designers of Alstom were aware of the needs and were creative enough to adapt their design to the new demands.

Tram Drivers’ Comfort

245

FIGURE 20.6 Reality has no surprises anymore.

Of course the expectation is that the tram drivers will experience a comfortable cab and — of greater importance — that the cab will be safer, because drivers have a good view of the traffic. The first impression driving with the tram, was that it had no surprises anymore (Fig. 20.6). RET designed their subway cab in a comparable way, and this resulted also in a comfortable and safe workplace for the drivers and other participants in the traffic environment.

REFERENCES Bronkhorst, R.E. and Krause, F. (2002) “End-users help design mass transport seats.” In Human Factors in Seating and Automotive Telematics (SP-1670). SAE World Congress, Detroit, March 4–7. SAE Technical Paper Series 2002-01-0780, 1–6. Warrendale, PA: SAE. Wilson, J.R. (1995) “Solution ownership in participative work design: The case of a crane control room.” International Journal of Industrial Ergonomics, 15: 329–344.

21

Redesign of EarthMoving Machines: It’s Also in the Details F. Krause, M.P. van der Grinten, K. Reijneveld, and R.E. Bronkhorst

CONTENTS 21.1 21.2 21.3 21.4

Introduction ................................................................................................248 Method........................................................................................................248 Results ........................................................................................................249 End-User Opinion on Improvements in the Paus Machine ......................249 21.4.1 Subjects ........................................................................................249 21.4.2 Ingress and Egress .......................................................................250 21.4.3 Seat...............................................................................................250 21.4.4 Steering Column ..........................................................................251 21.4.5 Dashboard ....................................................................................252 21.4.6 Controls........................................................................................252 21.4.7 Climate .........................................................................................253 21.4.8 Mirrors .........................................................................................254 21.4.9 Noise ............................................................................................254 21.5 End-User Opinion on the Kaiser Machine Improvements........................255 21.5.1 Seat...............................................................................................255 21.5.2 Ingress and Egress .......................................................................256 21.5.3 Pedals ...........................................................................................256 21.5.4 Joysticks .......................................................................................257 21.5.5 Front Window ..............................................................................257 21.5.6 Heat Regulation ...........................................................................258 21.5.7 Noise ............................................................................................258 21.5.8 Retest Results for ETEC .............................................................259 21.6 Conclusions ................................................................................................259 Acknowledgment ...................................................................................................261 References..............................................................................................................261

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This work is reproduced with permission of TNO, Copyright 2004.

21.1 INTRODUCTION Chapter 19 describes the development of a new machine for 2015. However, increasing comfort does not always require a very expensive and impressive improvement. In this chapter, minor changes in vehicles are introduced to reduce discomfort and improve comfort. To keep up with large competitors, small- and medium-sized companies have the advantage that they are closer to clients and can adapt faster to their needs. Further innovation in this field could make the difference in being able to sell competitive wheel loaders in the future. With this in mind, Maschinenfabrik Paus GmbH (Germany), Van Vliet BV, manufacturing ETEC machines (the Netherlands), and Kaiser AG (Liechtenstein) formed a consortium. These are European medium-sized (<250 employees) manufacturers of earth-moving machinery. Together with TNO they founded the Eurocabin project, which was partly funded by the European Union. The goal of this project was to further innovate and optimize the cabins of their machines. Because musculoskeletal injuries (Oliver, et al. 2000) are a major problem among earth-moving machinery drivers, special attention was paid to comfort and the prevention of work-related musculoskeletal injuries.

21.2 METHOD Based on previous studies (Vink and Kompier 1997; Noro and Imada 1991) (Chapter 4), several steps were defined to result in the production of better machines: 1. Step 1: Kick-off and project definition In this step the project was structured, appointments were made, and tasks divided. 2. Step 2: Orientation In this step, existing knowledge was studied in the literature and discussions were held with experts. An overview of trends in comfort and design in the automotive industry was conducted to identify issues relevant to earth-moving machines. The aspects to be studied were also defined. 3. Step 3: End-user opinion More than 300 operators were questioned regarding comfort aspects of earth-moving machines (Kuijt-Evers, et al. 2003). For the specific machines of Paus, Etec, and Kaiser, additional interviews were held with their end users (see Fig. 21.1). 4. Step 4: Expert opinion A group of experts examined the machines, sometimes with specific evaluation methods to study the fit (with ergomix), or to study vibration and noise. 5. Step 5: Adaptation proposals Based on the end-user opinion and expert evaluations, the main problems on the specific machines were described and improvement proposals were defined.

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FIGURE 21.1 Discussions with end users.

6. Step 6: First redesigned machines Based on the advice generated in Step 5, some machines were redesigned and were tested by end users again. 7. Step 7: Implementation in the new production process In this step the companies decided which changes would be standard in the new machines, which ones could be bought as an additional feature, and which ones would not be implemented.

21.3 RESULTS The process followed the steps as described in the method. In this section most attention is paid to the results of Step 6, which shows the specific changes. The processes of change have been described extensively in previous chapters (see also Krause et al. 2003) and will not be repeated here. The results will be described for the Paus and Kaiser machines, but because the ETEC machine had similar changes, only a table with ETEC results will be presented. In general, the elements that were found to need improvement in Chapter 2 are also taken up in this study: seat comfort, vibration and damping, dashboard and displays, climate control, what the machine looks like, cab dimensions, interior space, getting in and out, noise reduction, view, adjustability of seat and controls, and reliability.

21.4 21.4.1

END-USER OPINION ON IMPROVEMENTS IN THE PAUS MACHINE

SUBJECTS

Three operators with experience in the old machine (Fig. 21.2) were asked to give their opinion about the new machine during a test.

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FIGURE 21.2 The Paus machine used in this study.

21.4.2

INGRESS

AND

EGRESS

From the previous steps it was known that ingress and egress often take place between 20 and 50 times a day. Each time, the height difference between the ground and the cabin (approximately 1.2 m) has to be mastered, so improving ingress and egress was considered to be important, with respect to both ease and safety. As an improvement, the climbing aid's grip diameter was increased to 25mm and the hand clearance between the climbing aid and cabin was increased to 65mm, thus improving the feel of the grip and the ease with which it can be grabbed, even while wearing gloves. The steps were also modified to make all step heights more or less equal, and a strip was added to each step that increased the step depth to improve stability for the foot (Fig. 21.3). Operators were mostly satisfied with the ingress-egress improvements (steps and grips). All operators find the new grips more comfortable, but all state that they still require the same amount of strength for ingress and egress. This can be explained by the fact that the height from ground and cabin is still the same. Operators find the new steps more comfortable and safe, although the new step heights require getting used to.

21.4.3

SEAT

The seat height adjustment range was lowered 30 mm to improve seating, especially for smaller persons. This was achieved by modifying the seat pedestal, and additional elevation of the seat can be effected by means of spacer blocks if necessary. The lowered seat height was mostly appreciated, but one small operator, surprisingly, was not pleased with the new height. He liked to use the seat in the highest position to be able to have a good view of the ground and the shovel, because otherwise he had less of a “feel” for the machine. This problem can be explained by the fact that more than one driver often uses this type of machine, generally for short periods of

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FIGURE 21.3 The step modification (A, old situation; B, new situation).

time. For these short-term drivers it is harder to acquire the same feel for the machine that an experienced driver has.

21.4.4

STEERING COLUMN

A steering column that could be adjusted for height and inclination was installed (Fig. 21.4A). At the same time, changes were made to the dashboard support, the

FIGURE 21.4 The new adjustable steering column (A) and related modifications (B).

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FIGURE 21.5 Dashboard improvements.

support structure in the cabin floor, and the cabin matting (Fig. 21.4B). This was done to reduce rattle, an annoying feature of the older cabin. The new adjustable steering column is very much appreciated. All operators found that it enabled them to improve their seating position in the cab. Additionally, operators all agreed that ease of ingress and egress was improved because the steering wheel folds away with one easy lever movement, increasing the space for body movements.

21.4.5

DASHBOARD

The instrument board was changed completely according to TNO’s design suggestions (Fig. 21.5). This required constructing a new casing; regrouping gauges, control lamps, and switches; changing electric wiring; and building a new steel support for the casing. In the redesign process and in the manufacturing, careful attention was paid to avoid rattles and squeaks in the new dashboard. Other aspects considered in the design were avoiding reflections and making the machine easy to maintain. The latter was important because eastern Europe is a target market where owners mostly do their own servicing. Operators evaluate the new dashboard as equal to the former model. They do not notice the improved layout of gauges and switches, most likely because the amount of time spent looking at the dashboard is very small. Furthermore, the quality and speed of their work is not affected by the way the dashboard is laid out. They do find the new dashboard more appealing to the eye than the previous model.

21.4.6

CONTROLS

The possibilities for adjusting the joystick relative to the driver are now limited, due to the design of the control console. Adjusting the seat for optimal viewing and operation of pedals could result in a suboptimal joystick position. Therefore, additional adjustment of the joystick or control console was proposed. Grammer, a large manufacturer of operator seats, cooperated in the project and came up with a new and important prototype seat that has a multiadjustable armrest to which the joysticks can be attached. Such a system is preferred because a seat adjustment will not lead to a changed position relative to the joystick. Furthermore, the adjustability of the joystick

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relative to the driver is increased and the seat offers good arm support. Unfortunately, this improvement could not be built in time to be included in the test machine, and therefore it was not tested in this study.

21.4.7

CLIMATE

In the Paus machine, as in the other tested machines, climate was a point often mentioned by operators. Due to the large glass surfaces, heat buildup can easily take place on sunny days. Therefore, many operators would appreciate having air-conditioning in their cab. Installing air-conditioning is not necessarily a solution to the problem, however, because operators prefer to work with the door or window open to improve the outside view, communications, and sense of space. The desire for air-conditioning is also likely to be connected to the fact that the operators’ own luxury cars often have air-conditioning as a standard feature. In most earth-moving machines, air-conditioning is already optional. Installing air-conditioning as a standard feature was economically not feasible. A simple and feasible measure to at least reduce blinding by the sun was attaching green sun-protection foil to the upper part of the windows. Another problem the operators reported was insufficient defrosting of the windows. New air routing systems to improve defrosting and defogging were built into the machine. The defrosting unit was changed to create more vents and lifted to be more effective. Two additional vents were especially needed to defrost the side panels of the front window (Fig. 21.6).

B.

FIGURE 21.6 (A) The old defogging unit was most effective in window areas unused by operators. (B) The improved defogging unit is lifted and has additional vents for better defogging of front window side panels.

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FIGURE 21.7 Mirror suspension (A, old inflexible situation; B, new flexible situation).

21.4.8

MIRRORS

The mirror suspension was a problem in the old machine. The inflexible part of the suspension protruded too far from the cab and the flexible part was too small (Fig. 21.7A). Mirrors and the mirror suspension were often damaged. The improvement is shown in Fig. 21.7B, and operators all consider it to be better than the older system. The risk of damaging cab structures when the mirrors collide with a tree or similar protruding object has significantly decreased. The view seen in the mirrors remained the same.

21.4.9

NOISE

The following measures have been taken to reduce interior noise: •

• • •

The flexible sealing used to connect the three windows that form the front and rear windows was replaced by a stiffer glue to reduce resonance when the engine is idling. The steering column and instrument casing were designed and mounted to avoid rattle and squeak. Insulating material under the cabin’s bottom made it thicker (from 15 to 30 mm). Openings around the engine were closed and measures were taken to dampen the engine air intake and engine cooling. Careful attention was paid not to disturb the engine’s heat balance.

The measures that were taken to reduce interior noise in the cabin have had a positive effect, according to the operators. They all find that the sound level is lower and more pleasant in the new machines.

Redesign of Earth-Moving Machines: It’s Also in the Details

21.5

255

END-USER OPINION ON THE KAISER MACHINE IMPROVEMENTS

Four subjects experienced in operating the original Kaiser machine (Fig. 21.8) tested the new machine.

21.5.1

SEAT

The choice of seat supplier is limited. There are only a few major players in the market. From questioning the operators it became clear that operators in general rated the seat itself as fairly comfortable. Improvements were desired with respect to the following aspects: •

•

•

Armrests. They were considered to be very important. The seat offered sub-standard armrest adjustability and comfort. Some seats come without armrests in which cases armrests are often fitted onto the joystick console (Fig. 21.9). Operators often complain about the width, hardness, and improper height of armrests. Adjustability. Adjustment levers are often not easy to reach and require too much pressure to be operated. Also, it is often unclear what the lever’s function is. The weight adjustment of seats with mechanical springs is difficult. As a result, the adjustment is often not done. Suspension. Seat suspension can still be improved. Several operators complain about the seat bottoming out, which leads to peak forces on the lower back. Also, the damping characteristics of air-suspended seats change with the chosen seat height.

Obtaining these improvements was not possible within the parameters of the project. Buying a more expensive seat from the seat supplier would not necessarily

FIGURE 21.8 The Kaiser excavator used in this study.

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FIGURE 21.9 A console mounted armrest has poor adjustment qualities (here mounted in a wheel loader).

solve the problems, and the market being as competitive as it is, construction companies are not willing to pay for many extras. One improvement could be made, however. The seat’s adjustment range was larger than needed, and by restricting the range extra storage space was created in the very confined space of the excavator cab.

21.5.2

INGRESS

AND

EGRESS

The climbing aid grips were also improved in the Kaiser machine. This was expected to be an improvement because operators step in and out of the machine 20 to 50 times a day. The grips were extended downward so operators could catch them while standing on the ground or climbing up one of the legs in steep terrain. In general, the extended grip was appreciated by all but one of the test operators. That operator found the grip to be no better than the older type. Surprisingly, the questionnaires show no increase in safety experienced by operators using the new grip. This may be caused by the fact that the prototype was scarcely tested in very steep terrain, where the new grip would best show its advantages. The retest further revealed a new operator wish that was not recognized in the first testing. The test operators also wanted to have a grip on the left inside surface of the door opening. This modification is being further investigated.

21.5.3

PEDALS

This type of excavator is designed to work in very difficult terrain (Fig. 21.8). Footrests were added to improve operator support possibilities while working with the machine in a tilted position. Also, the outer pedals were turned 10° to enable a more neutral position of the leg and foot (Fig. 21.10). A foot switch that required frequent pushing and 90° turning was removed, and its function was allocated to a

Redesign of Earth-Moving Machines: It’s Also in the Details

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FIGURE 21.10 The position of the pedals (A, old configuration; B, new configuration).

joystick switch. Though they corresponded to a more natural foot position, operators did not find the changed position of the pedals better than the parallel position. On the other hand, they did not find them to be worse. Operators appreciated the fact that they no longer had to operate a switch with the foot, but they had varying opinions about the new footrest to the right. Some said it was not needed. However, because it hardly obstructs the operator’s view they agreed that it should be left in place. The new footrests in front of the tilted foot rests are appreciated by the shorter operators, although the new rests should be extended a bit toward the operator. One operator stated that he likes the seat up high so the air suspension in the seat works properly. With the new footrests, it is easier to reach the floor.

21.5.4

JOYSTICKS

In the old situation there was a thumb-operated switch on the joystick that needed frequent depressing during longer periods of time. This was replaced by a switch operated by the index finger (see Fig. 21.11A and B) thus improving its position. By doing so the foot switch mentioned earlier could be replaced by a joystick switch to improve handling and reduce leg load. This switch had approximately the same position as the first mentioned thumb-operated switch, only higher up on the joystick to improve thumb position (see Fig. 21.11C). In a meeting, the opinion of six experienced operators was asked, and their answers checked by an expert, as to whether different hand sizes could operate the switches safely. With respect to joysticks, operator preferences vary greatly. A consensus was reached that the new joystick would definitely need getting used to, but it was better than the existing one. The switches have a better position and the joystick is lighter, so the operating force can be reduced and it fits more hands than the older type.

21.5.5

FRONT WINDOW

The window opening mechanism was improved, thus significantly reducing the load on the operator’s shoulders and back. The standard pane was replaced by special

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Comfort and Design: Principles and Good Practice

A.

B.

C.

FIGURE 21.11 The frequently used thumb-operated switch on the joystick (A) was replaced by an index finger operated switch (B). The foot switch was replaced by a joystick switch (C: lower middle switch).

heat-reflecting glass that reduced radiant heat buildup in the cab. Half of the test operators found the changed window-sliding system easier to operate, but the other half found it equal to the older type. One operator who found it easier said he also believes that an operator has less control over the closing of the window when the cab is tilted forward. The effect of the heat-reflecting glass could not be evaluated at the time.

21.5.6

HEAT REGULATION

The position and design of the air vent near the feet was changed in order to prevent inadvertently closing the vent with the foot. Also, heat regulation in the cab was difficult because of a hard-to-control regulation switch. The regulation switch was replaced by a better one, and all operators find the new position of the air vent to be better. They also found that the new regulation switch enabled them to adjust the temperature better than before.

21.5.7

NOISE

Several measures were taken to reduce noise in the cab (Fig.21.12). Though measurements revealed that the interior sound level decreased by 5 dB inside the cab, most operators had not noticed this due to the fact that they mostly work with either

Redesign of Earth-Moving Machines: It’s Also in the Details

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FIGURE 21.12 The padding of the cab’s outside floor (A) and side (B) panels with sound insulating material around the engine.

the front window or the door open. Measurements had been made with both door and window closed. Surprisingly, the retest brought another fact to light that had not been noticed previously. One operator experienced an increase in cab noise while working with an opened front window rather than a closed window. The noise increase observed may well have been caused by the reflection of cab noise from the window. When it is open, the window covers the padded ceiling of the cab. This noise phenomenon certainly deserves attention in the future.

21.5.8

RETEST RESULTS

FOR

ETEC

The changes to the ETEC machine will not be explained here, because they are similar to changes made in the Paus and Kaiser machines. Six subjects experienced in operating the original ETEC machine tested the new ETEC machine. Table 21.1 gives an overview of the results. Improvements in grip, view, and noise reduction were evaluated as especially positive.

21.6 CONCLUSIONS The improvements discussed in this chapter are, in fact, details. However, these details solved problems mentioned by end users, and in the retest the end users mentioned that most details had a positive effect on comfort, and even on work output. The retests showed that, as a whole, the improved prototypes provide better cab comfort than their predecessors, due to the various small improvements in the seat, controls, climate, view, and noise level. An important step in work-related musculoskeletal risk reduction in the arm was taken in collaboration with seat manufacturer Grammer, who designed a multiadjustable armrest on their seat to which a joystick can be mounted. This was the first seat-control system for earth-moving machinery in which armrests and joysticks are adjusted together. Both are thus easier to adjust by the operator and offer better positioning of the controls relative to the operator.

260

TABLE 21.1 Overview of the Opinion of Six Operators in the Retest ETEC retest results ingress–egress grips

front window: opening

view: rooftop window

noise

improvements

op. = Operator 1 = better, 2 = equal, 3 = worse, 4 = no opinion question rooftop window. 1 = good, 2 = reasonable

op. 2 1 1 1 2 1 1 2 1 2 1 1 1 1 1 1 1

op. 3 2 1 2 2 1 1 2 2 1 1 1 1 1 1 2 1

op. 4 2 1 2 2 1 1 2 1 1 1 1 1 1 1 1 1

op. 5 1 2 1 2 2 1 2 1 1 1 1 1 1 1 1 1

op. 6 1 1 1 2 1 1 2 1 2 1 1 1 1 1 1 1

# of answers better equal 3 3 5 1 3 3 1 5 5 1 6 0 1 5 5 1 5 1 6 (good) 0 6 (good) 0 6 (good) 0 6 0 6 0 5 1 6 0

Comfort and Design: Principles and Good Practice

view: window sill

general techn construction ingress-egress comfort muscle load techn construction view on work techn construction position of grips muscle load techn construction view through window usability next to the machine in cabin with door closed sound comfort effect on work output

op. 1 2 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1

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In the final meeting of this project the companies mentioned that they considered the retest to be a very important part of the project. Information from the retest made the effects of improvements explicitly known to the manufacturers. Although the improvements were based on problems mentioned by end users, they did create a changed cab. Only retesting by the end users could reveal whether the right adjustments to the cab were made. With this information, manufacturers are better able to make plans for their future products, which is very important considering the competition in this market sector.

ACKNOWLEDGMENT The authors wish to thank the EU (Mr. Katalagarianakis), Paus GmbH, Kaiser AG, and ETEC (Van Vliet) for their support and collaboration.

REFERENCES Krause, F., Bronkhorst, R.E. and Looze, M.P. de, eds. (2003) Comfortable Earth-Moving Machinery, Hoofddorp: TNO. Kuijt-Evers, L.F.M., Krause, F. and Vink, P. (2003) “Aspects to improve cabin comfort of wheel loaders and excavators according to operators.” Applied Ergonomics, 34(3): 265–272. Noro, K. and Imada, A. (1991) Participatory Ergonomics, London: Taylor & Francis. Oliver, M., Richards, J. and Biden, E. (2000) “Off-road machine controls: Investigating the risk of carpal tunnel syndrome.” Ergonomics, 43(11): 1887–1903. Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic experiment in a naturalistic setting.” Ergonomics, 40(4): 435–449.

of a Future 22 Concept Nissan Car Interior B.J.A. van Haperen, P. Vink, C.J. Overbeeke, J.P. Djajadiningrat, and S.H. Lee CONTENTS 22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 22.9 22.10 22.11 22.12

Introduction ................................................................................................263 Experiential Design....................................................................................264 Influencing Experience...............................................................................265 People .........................................................................................................265 The Car.......................................................................................................266 The Environment........................................................................................268 Time............................................................................................................268 Summary of People–Car–Environment–Time ...........................................269 The Idea Phase ...........................................................................................269 Three Elaborated Concepts ........................................................................269 Toward the Final Design............................................................................271 Final Concept .............................................................................................271 22.12.1 Collecting Information on the Environment...............................................................................272 22.12.2 Select and Watch .......................................................................274 22.12.3 Ending the Experience ..............................................................278 22.12.4 The Exterior...............................................................................278 22.13 Conclusions and Discussion ......................................................................278 Acknowledgment ...................................................................................................280 References..............................................................................................................280

22.1 INTRODUCTION The previous chapter demonstrated the effects of small changes on the experience of comfort. Of course this is important to achieve short term effects, but to stay ahead of competitors long term developments are needed as well. This chapter describes the process of designing a more future-oriented car interior. Car manufacturers have to be very competitive to keep, and preferably expand, their market share; new products are a must. To find out which new products will 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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be successful, concept cars are often shared with future buyers. In this study, the development of a concept for a new car interior is described. The project is a collaboration between Nissan, Creative Box Inc., and the industrial design faculties of the Delft University of Technology and the Eindhoven University of Technology. Creative Box Inc. is perhaps not so well-known and may need some introduction. Car Styling magazine sharply described Creative Box as Nissan Design’s “think-tank.” Most of the work of Creative Box, mainly the design of new concept cars for various motor shows throughout the year, is commissioned by Nissan. In this project, Creative Box was interested in the design of a new concept interior for young people living in Tokyo. The approach that was used in this project is the experiential design approach (Overbeeke et al. 2003). As discussed in Chapter 2, discomfort is more related to physical characteristics, whereas comfort is more related to experience, emotion, unexpected features, and luxury. The experiential design approach is particularly interesting in regard to comfort, and is therefore also described in this book. This chapter first presents a short description of experiential design, followed by an orientation to the possibilities for innovation in the car interior. Based on this knowledge, new ideas were generated that led to a final design concept.

22.2

EXPERIENTIAL DESIGN

The experience of a person is the basis for the design in the experiential design approach. In this case, the experience of the car interior is the central issue. A car ride is more than just getting from point A to point B. It is a total experience. In traditional design methods the designer often provides a package of functions (the car) that is presented to the user, with the main objective being to let the user understand the functions (Fig. 22.1). Experiential design focuses on the quality of the user’s experience during the whole period of engagement with the product (Fig. 22.2). In order to experientially design a product, first, the (desired) experience must first be clear to the designer. But what exactly is an experience? The dictionary (www.dictionary.com) is very clear on this subject: Experience is the apprehension

System Image (product)

Design Model

FIGURE 22.1 Traditional design.

User's Model

Concept of a Future Nissan Car Interior

265

System Image (product)

Design Model

User's Model

FIGURE 22.2 Experiential design.

of an object, thought, or emotion through the senses or the mind. Although one might argue about the exact wording of this definition, the keywords are obvious: object, emotion, senses, and mind. Everybody has the same sensorial apprehension of an object, but our experiences are different because for each person different emotions are elicited.

22.3

INFLUENCING EXPERIENCE

The car is not the only factor that has an influence on the experience of the ride. In the definition of experience it was already mentioned that an experience differs strongly between individuals. However, the total experience of sitting in the car is also different from being outside of it. The environment that is passed by while driving also influences the experience. Finally, the experience changes over time as well. An enhanced car ride should link these factors — people, car, and environment — through the whole period of the car’s use. One might say that a bond between the factors should be elicited. In the next paragraphs, these factors and their influence on the experience are described in more detail.

22.4 PEOPLE Most designers are aware of the difference between people and their wishes. This study focuses on young people living in Tokyo, because this is the target group for the new interior. Based on observations and on interviews with people familiar with the area, the group can be given the following description. The Tokyo districts Shibuya, Shinjuku, and Harajuku especially are inhabited by some of the most fashionable people in the world. Night and day, people between 20 and 30 years old dominate the streets. These are the trend makers, or early adapters. They spend a lot of time with friends (family is less important), and they are always looking for a good time in life. Contact with others is very important, and seeing and being seen is crucial! These attitudes are also important in terms of the products they use and buy. Whether the products are for daily use or for a special occasion, both personal pleasure and expressing a desired image to others are extremely important.

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22.5 THE CAR The enhanced car ride is not a new concept to manufacturers. Several designs already emphasize this approach. Next to the popular small cars, there is a trend toward (bigger) interiors with a secondary function that is not so closely related to driving (Figs. 22.3 and 22.4). These interiors are made both for recreational purposes and for professional use. An example is the Ford Galaxy, which has power outlets and seats that can be changed into worktables. Technical developments also support the interior designer. Smaller engines — maybe even integrated into the floor panel (Fig. 22.5) — and smart construction with more use of plastics, for example, offer greater volume and additional possibilities for the interior. Also, the more organic interiors that are within reach because of these new production techniques have drawn the interest of the designers (Fig. 22.6). One of the best-known current examples of a car that tries to adapt with our emotions is the Toyota POD (Fig. 22.7). In this concept car, activity within the car and the driving style are used to capture or display emotion. For example, the lights

FIGURE 22.3 Isuzu Funkybox: a mobile recreation room. (Courtesy of Isuzu.)

FIGURE 22.4 Renault Ellypse: a very plausible solution for relaxing in a car. (Courtesy of Renault.)

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FIGURE 22.5 General Motors’AUTOnomy: fuel-cells, engines, and steering combined into one. (Courtesy of Car Design News: www.cardesignnews.com)

FIGURE 22.6 BMW CS1: A more organic use of materials. (Courtesy of Car Design News: www.cardesignnews.com)

FIGURE 22.7 Toyota’s POD is one of the first examples of a new implementation of electronics. (Courtesy of Toyota.)

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on the exterior of the car change color according to the driver’s behavior. Still, this concept focuses mainly on measuring and displaying emotions—not on influencing emotions or interacting with the passengers or driver. Finally, the application of electronics continues to grow in many cars. Most currently used techniques have been available for ten years, but they have become really affordable only in the last few years. The use of the electronics still has room for improvement, because it is not always optimally adapted to the user’s needs and wishes. When a person needs to press the same button eight times to change from radio to CD player, or to adjust the air conditioner, there is an obvious gap between what really works and what is useful.

22.6

THE ENVIRONMENT

The cars belonging to people who live in large cities usually are not just for driving within the city. Public transport is often more convenient and faster. However, when people take a trip with others to a location outside the city, for example, the flexibility of the car is preferable. It is therefore likely that a car bought by young people in a city will mostly be used for that purpose. During those car rides, there is a great difference between the part in the city, and the part on the (open) highway. The ride usually starts in the city, where it is very crowded, and many things can happen. The city is an interesting place to drive through, but the high buildings, traffic lights, neon signs, and crowds sometimes generate too many impressions. Contact with people outside the car is brief, but close. All this is in contrast with the highway, which may be relatively empty. The roads are straight, and the sound shields at the sides of the road often create a boring view. Contact with people in other cars may last for a longer time, but at a greater distance. On this highway portion of the ride the interior of the car, and the travelers inside it, become more important. The focus shifts from outside to inside.

22.7 TIME Time in relation to a car can be divided into short-term and long-term contact. Longterm contact can be defined as the relationship, or bond, that a person has with the car. The bond is created because the long-term contact consists of all of the moments of short-term contact. In this study, we take one car ride as the definition of shortterm contact. First the person approaches the car, opens the door, takes a seat, and prepares to ride. Next, the trip begins by starting the car and driving through different environments, adjusting controls in the car, picking up friends, and communicating with others. This communicating and sharing of experiences is seen as very important to the target group of this study. Finally, the destination is reached, people get out and the car is locked. This is the actual end of the experience. Realizing this it is obvious that a car ride is more than just driving. The ride can be divided into three phases: initiate, travel, and end. It is clear that the experience needs to be enhanced throughout the whole process, not just during the travel phase.

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22.8 SUMMARY OF PEOPLE–CAR–ENVIRONMENT–TIME The previous paragraphs explained that in order to fully influence the experience of a car ride, four important factors need to be taken into regard: people, product, environment, and time. The future users live in a world where it is important that products provide both pleasure and the possibility to express a desired image. For young people this means a rapidly changing style and interest. Current technology provides more freedom for designers to meet these wishes. Electronics are more frequently seen, and spacious interiors with more flexibility have been introduced. When the car is used, two main environments are encountered: The crowded city with many impressions and the boring, less interesting highway. Especially in this last area the car can provide a more exciting experience. Regarding the aspect of time it is important to realize the complete car-user interaction must be considered: from approaching the car to stepping away from it after the ride. With this knowledge the basis for new ideas to enhance the experience of the car ride was formed. How these ideas were elaborated is described in the next section.

22.9 THE IDEA PHASE In this phase, several uncompromising new ideas were created for enhancing the car experience. To begin with, sketches were created with one car ride as a starting point. In this car ride, contact with the car was conducted as if the car were a human friend. This resulted in the insight that such contact should be about two-way interacting, not just an action-reaction event. To achieve this interaction, a conceptual way of designing was used that resulted in somewhat wild, but inspiring, ideas. For instance, instead of a person having to put on a safety belt, the car actually hugs the person, creating a warm and welcoming feeling. These different ideas were shown to potential users and other designers. Based on their comments and reactions, a second and more realistic range of ideas was created. This resulted in seven main concept directions. Of these, three illustrative concepts are described in the following section.

22.10

THREE ELABORATED CONCEPTS

1. Direct contact with people (Fig. 22.8) This idea focuses on enhancing communication between persons. In current cars communication between the front seat and the rear is not comfortable. To enhance communication the interior of existing cars can be transformed, but this transformation needs to take place before the ride starts. Communication within a group is often not a planned action, according to a predefined pattern. By giving the user the opportunity to flexibly adjust the interior while driving, optimal communication conditions can be realized at any time.

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FIGURE 22.8 A flexible interior for better communication and a spacious feeling.

2. Personal settings vs. group controls (Fig. 22.9) Communication with the car and with other passengers can also be influenced by controls. Personal settings can be made real personal by placing them close to, or actually on the body. In a practical situation these personal controls could be built into the safety belt. Not only do others keep their hands off your controls, but also the bond with the vehicle is genuinely improved. And, as an advantage the user has an extra reason to wear the safety belt. In contrast to personal controls are group controls. By sharing functions such as the car’s audio system, the interaction between people in the car is improved. In both ideas controlling the car has an influence on the way

FIGURE 22.9 Adjust the setting in an interesting, social way.

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FIGURE 22.10 An open car for direct contact with the environment.

people interact. Next to the location of the controls, the way these controls are operated can also be improved. Making digital controls more physical creates controls that are easier to understand, and more fun to use. For instance, one can actually place the next song into the radio system or turn a speaker to open it and get more volume. 3. Direct contact with the environment (Fig. 22.10) A bigger window surface, or even an open body, can improve the direct contact with the environment. It is not only easier to look outside, but it is also easier for people outside to see the people inside the car.

22.11

TOWARD THE FINAL DESIGN

Seven ideas, including the three mentioned above, were shown to Japanese and Dutch designers and students — all young people living in an urban area. The discussions that followed led to the understanding that almost all ideas have potential, although some of them are just a support to the bigger picture. The flexible car interior, for instance, provides the necessary freedom to have more contact, but it was not seen as a really exciting new concept. However, the freedom does help to get an enhanced experience up to a certain level. In fact, the designers and students pointed to using multiple ideas into one concept. Therefore, many ideas were combined to create one design in which enhanced contact with the environment is the main concept. How this enhancement is controlled, and how it influences the social behavior inside the car is based on the ideas described in the previous paragraph. The final design constrains the styling of the car as little as possible. Different cars can have the same elements, but with different styling. A style-free concept shows that the design ideas can be applicable to many cars. This notion is further clarified in the following section.

22.12 FINAL CONCEPT The final concept is presented with the future in mind, a future where cars can drive automatically. Nowadays, experiments are conducted in which cars can click together into trains on the highway and drive with a fixed distance between them. Such

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FIGURE 22.11 OLED, a display on glass.

systems will become more and more advanced in the future, which means that everyone in the car will have the freedom to communicate or to do other things without risk. A flexible interior will help them to turn the seats and face each other, or to have a better look outside. The car windows and roof in this final concept are big displays. Future organic light-emitting diode (OLED) technology will be able to create a display on a simple piece of car window glass (Fig. 22.11). When the driver walks toward the car, this display becomes transparent, as if the car is welcoming the driver with an invitation to come inside (Fig. 22.12). The most important aspects of the final concept are: how the information is collected, how the user handles the data, the way the ride ends and how the exterior will look to others. All these were designed with the user experience as a basis.

22.12.1

COLLECTING INFORMATION

ON THE

ENVIRONMENT

As described earlier, the city provides an overflow of information to the driving experience, whereas the highway is much quieter. In order to create a better balance, the overflow of information can be taken from the city to the highway. When the

FIGURE 22.12 The car opens as you approach.

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FIGURE 22.13 A location-based surface (LBS).

car drives through the city it passes many sources of information that are surrounded by location-based surfaces (Fig. 22.13). Whenever the car drives through such a surface, an internet-like connection is opened and a small image (thumbnail) is projected onto the roof. These images create a riverlike flow of information from the front of the car to the rear (Fig. 22.14). By adjusting the width of this river, the amount of received information is controlled.

FIGURE 22.14 Information flows from front to rear, over the roof.

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FIGURE 22.15 Widening the info-zone with physical controls.

In making such an adjustment, the combination between physical controls and the digital world is very important. When the information river is turned off, the sliders (Fig. 22.15) are locked together, but a small part of the display remains turned on. Because of the physical groove and the visibility of the display, the user easily understands that the sliders can move, and that they can control something on the display. This provides the necessary feed-forward and inherent feedback of information (Djajadiningrat et al. 2002). Figure 22.16 shows the many information sources in the city. The size of the location-based surfaces around these sources depends on the width of the sliders (left and middle). The figure also shows the amount of sources differs from the city to the highway (right). In order to keep getting information the LBS’s are bigger. People in cars still receive information while on the highway, only less. The information is very diverse. It has to be provided by a variety of different sources, and just one source can provide different kinds of information (Fig. 22.17). Sources can be movie theaters, stadiums, libraries, stores, and museums, among many other things.

22.12.2

SELECT

AND

WATCH

Now that the information is on the roof, it can be browsed through. Simple, easy-todetect hand movements can shuttle the information flow back and forth, as in Fig. 22.18. A thermal CCD, which is a sensor that creates a digital image from a heat pattern, detects the hand movements.

FIGURE 22.16 LBS locations in the city (left and middle) and on the highway (right).

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FIGURE 22.17 Information is place- and time-dependent. A stadium (left) will provide different information than a movie theater. The information from the stadium will also differ from time to time. Examples of the information that can be provided are: (top) views you never get from the car, (middle) yesterday’s concert fragments, and (bottom) player information.

In case an interesting piece of information appears, it can be pulled to the side window for a closer look. At the sides of the preview area on the roof, there are openings for scrolling the information (again providing necessary feed-forward). To transport the information from the roof to the side window, the roof pillar barrier must be crossed by using a so-called transporter.

FIGURE 22.18 Browsing through content.

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FIGURE 22.19 The transporter.

The transporter is a physical object that has a number of functions. First, images can be viewed in sequence and can be locked onto the window like wallpaper. The procedure is very simple: Just turn the transporter, and thus remove the path. Second, the transporter (Fig. 22.19) can store an image, clip, or sound. This is done simply by sliding information into one of the side pockets (Fig. 22.20). When a clip is stored, the transporter can be taken off the pillar and given to somebody else in the car for viewing (Figs. 22.21 and 22.22). This physical interaction is natural, is easy to understand, and improves the social contact in the car. When a piece of information is watched, it can also be rated good or bad. This is done by pressing the thumbs-up or thumbs-down images that appear when a hand moves close to the side window. The car then filters new information that enters the car according to the user profile that is built from these ratings. It is as if the location-based surfaces all have a different size for each car (Fig. 22.23). Some sources will be missed when the car isn’t close enough, but interesting sources can be farther away and the information can still be received. Note that the user profile is bound to the car, not to the individual users. Since the owner uses the car most often, the profile will be closest to his or her wishes — although there may still be some surprises!

FIGURE 22.20 Putting content into the transporter.

Concept of a Future Nissan Car Interior

FIGURE 22.21 Exchanging transporters.

FIGURE 22.22 Pushing information out.

FIGURE 22.23 Rating information to create a user profile.

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FIGURE 22.24 Information fades away.

22.12.3

ENDING

THE

EXPERIENCE

At the end of the car ride, the experience also comes to an end. This means that there is no need for further information, and it can just disappear. Of course, the information stored in the transporters can be saved, but the rest is gone forever. The information doesn’t just disappear right away when the car comes to a stop. Sometimes one needs to stop for gas, or to buy a snack and stretch the legs, or to have a cup of coffee. Thirty minutes is normally more than enough time to do these things and start the car again with no information lost. If the car is stopped for a longer time, the information fades away (Fig. 22.24).

22.12.4

THE EXTERIOR

The information flow is interesting not only for the people inside the car. When the car passes by, it will also draw the attention of people on the sidewalk. This means that the people inside get the attention they want and the people on the sidewalk get an interesting view. But it would be a waste just to use this big display when the car is being driven. When the car is standing still, the display can be used for other purposes. A company can place advertisement on it, people can play the newest video games, or Nissan can use it to show their latest new models (Fig. 22.25). But why would one give away this display space? What’s the advantage to the owner? Obviously, advertisers are interested in crowded places, and parking fees are high there. An advertiser can pay this fee for the car owner, to the advantage of both parties! (For more movies and more information on this subject see www.bartvanhaperen.com)

22.13 CONCLUSIONS AND DISCUSSION The goal of this study was to create a new car concept for young people living in Tokyo. These youngsters and their experiences were analyzed. Using many sketches, an enhanced experience was researched and discussed with the youngsters and designers. Based on this process, a final concept was developed. This final concept

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FIGURE 22.25 Extra options while parking.

enhances the car ride and the experience young people have in their car, but in fact it might be applied to any car for any group of people. The new car concept provides many advantages for the user. It shows that using electronics can help people enjoy themselves more, and thus enhance their experience. But it has to be implemented in a subtle way. The TVs, DVD players, or even complete computer systems we see nowadays are not coupled to the driving process, and in that sense are not enhancing the experience. Next to that, the question is whether these items lead to an improved experience of comfort, or a better experience in general. Or is the experience of traveling traded for the experience of watching a TV? Taking information from the environment creates many new opportunities and possibilities for great improvement. Another improvement is in how the information is handled. Many interface designers still try to create a format that burdens the user with functionality. Technology allows for all these functions, but that doesn’t mean people want them, and most people hate to control screens with just one button. Separating functions and combining physical controls with the digital world not only creates an interface that is more fun, but one that is easier to understand as well. Of course, some unsolved questions still remain. Who should prevent so-called pirates from sending out viruses or, with less destructive results, spam? Who keeps track of the quality of the information? And why do people want to send out information in the first place? To these questions we have no clear answer. There will

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always be vandals, but since the information is location-based, tracing the source and shutting it down will be much easier. Also, by rating the information received the overall quality of the information will rise. Sources want people to look at their information, so they need to make it interesting. Finally, next to noncommercial sources that simply want attention, companies can learn very fast whether a new product, such as a movie, is popular or not — a good reason to create an information source. The concept discussed in this chapter might still seem far-fetched to some people, but the technology is closer than we think. Big OLED displays can be expected within ten years, and the CCD hand tracing is in its test phase already. What is certain, however, is that product design should take the lead in opening up these new technologies for the user. That is essentially what this chapter is about.

ACKNOWLEDGMENT Special thanks are extended to Creative Box Inc., and all their employees. They offered the opportunity to conduct this project at their offices, and without their help this chapter would not exist. Many thanks are offered also to all who helped in any way to finish this project.

REFERENCES Djajadiningrat, J.P., Overbeeke, C.J. and Wensveen, S.A.G. (2002) “But how, Donald, tell us how?” In Proceedings of DIS2002, London: 285–291. Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with added emotional value: Development and application of an approach for research through design.” The Design Journal, 4(1): 32–47. Overbeeke, C.J., Djajadiningrat, J.P., Hummels, C., Wensveen, S.A.G. and Frens, J. (2003) “Let’s make things engaging.” In Mark A. Blythe, Andrew F. Monk, Kees Overbeeke and Peter C. Wright, eds. Funology: From Usability to Enjoyment, Dordrecht: Kluwer.

and Benefits 23 Costs of Comfort Products for Professional Use E.A.P. Koningsveld CONTENTS 23.1 Introduction ................................................................................................281 23.2 Method........................................................................................................281 23.3 Case 1: Glaziers .........................................................................................283 23.4 Case 2: Cleaners in Home Care ................................................................285 23.5 Conclusions ................................................................................................287 References..............................................................................................................287

23.1 INTRODUCTION In the previous chapters, design processes and evaluations of products related to comfort and discomfort are described. This chapter focuses on the costs and benefits of these products. The general perception is that the implementation of improvements is hampered by a lack of consciousness of costs and benefits and by a deficiency of data (Jong 2002). Several models are available to study cost and benefits (Stanton and Baber 2003; Beune 2001; Koningsveld and Thé 2000; Koningsveld 2003; Koningsveld et al. 2002). In our research and consultancy projects our clients needed a rather simple model, which will be described in this chapter. First a general model is described, based on experiences in projects and the literature (Reyneveld 2001; Koningsveld 2003), followed by two examples in which costs and benefits are calculated. One example concerns a work situation in which discomfort by physical loads are evident. The second example concerns proposals to improve the work of cleaners in the home care industry.

23.2 METHOD The word costs indicates the actual costs in terms of money, as well as other efforts, that cannot be represented in quantitative terms but can be indicated by qualitative measures, such as attractiveness, increased health, or reduced discomfort. Benefits 0-8493-2830-6/05/$0.00+$1.50 © 2005 by CRC Press LLC

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can be productivity gains, lower costs, and higher quality, as well as nonquantitative advantages. There may be negative costs, for instance if a grant is received or if certain measures do not have to be taken when an improvement is implemented. For example, if a rolling carpet is chosen as the floor of a loading space in a van in order to decrease the discomfort of people who deliver parcels, the wooden floor that is usually ordered in a new van does not have to be bought. Benefits can also be gained by reducing costs. Negative benefits are possible as well, for instance in a case where the output of a work station is reduced by the implemented safety improvements. The aspects to consider in regard to the cost/benefit issue are • • • • • • •

Investments (consultancy, selection of solutions, purchase, installation, training, grants) Operating costs (maintenance, space, energy, interest, and personnel costs) Health (health complaints, lost working days, disability, insurance, and occupational rehabilitation) Safety (safety behavior, accidents, and near-accidents) Performance (productivity, output, time to market, lead time, service level, quality, flexibility, personnel turnover, and recruitment power) Liability (costs of processes, lawyers, penalties, and claims) Values, standards (image: “We pay serious attention to health and safety!”)

There are no general rules on how to value a parameter. For instance: what are the costs of a lost working day? Possible answers to that question include the following: • • •

The absent worker’s wages for that lost day. The production that was planned but not realized. The costs of a temporary worker. In addition, the differences in output quantity and quality between the regular and the temporary worker may be considered, as well as the costs involved in losing a client as a result of the mistakes made that day.

It is clear that in each individual case it is necessary to determine the real costs for all aspects, as well as the real benefits. Depending on the goal of a costs and benefits evaluation, the appropriate method can be chosen. A quick scan is adequate for a relatively small investment, in order to improve the work of one person or a small group. For long-lasting improvements with a wide scope, a more thorough assessment of factors and parameters is more appropriate. In general, if estimations have to be made, it is advisable to make them in close collaboration with the responsible management. They have easy access to data and are familiar with the business indices. Management involvement prevents the consultant from having to prove the data. Because management has taken part in validating the data, the outcomes are traceable and acceptable.

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23.3 CASE 1: GLAZIERS The work of glaziers is physically straining (see Chapter 6); it results in discomfort and in an unacceptable level of health hazard. In particular, the double panes that nowadays have become common are heavy. Over the past years several new tools and methods of transport have been introduced. These tools and methods were developed in a participatory ergonomics project (Urlings 1998). Despite a lot of promotional activities, the implementation of these improvements on the work floor goes slowly. Employers are reluctant, because they doubt their investments will be repaid. In a costs and benefits evaluation a set of tools was considered: 1) a simple crane mounted on the glaziers’ van to help hoist the glass on and off; 2) two carts, each of which has a specific application depending on the transport circumstances; 3) an aluminium hoisting unit ten meters tall for lifting panes vertically to the window frame; and 4) a new electric hand tool that eliminates the strain of manually cutting glass putty. All of these devices are always available in the van, so the workers themselves can choose which aids to use in a certain situation (Fig. 23.1). The investment leads to annual depreciation costs of €640 (Table 23.1). The time required to learn to work with the new methods is short and can be depreciated over many years. Therefore, the annual costs will be very small and are not taken into account (these are stated as pro memoria). The annual exploitation costs consist of an inspection of the crane and some maintenance for €200, so the total annual expenses amount to a total of 840 (Table 23.1). For the benefits, we look at the performance of the workforce. According to law, the maximum lifting weight is 25 kg per person. To handle and lift glass panes of

FIGURE 23.1 A simple cart for the transport of windowpanes by glaziers.

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TABLE 23.1 Investment, Depreciation, and Operating Costs of New Equipment for Glaziers Equipment Crane mounted on the van Cart 1 Cart 2 Electric glass putty cutter Aluminium hoisting unit Annual inspection, maintenance Total annual costs

Costs € 1250 € 150 € 250 € 300 € 1250 € 200

Depreciation time 5 years 5 years 5 years 5 years 5 years —

Annual costs € 250 € 30 € 50 € 60 € 250 € 200 € 840

more than 50 kg the regular team of two glaziers will need a third man, which indeed is the practice when necessary. Together with management it was estimated that the third man spends a total of 15% of his working time to get to and help a team of two glaziers. That represents 15% of his wages (€26,000/year). With the new tools and lifting devices no third man is needed, so the reduction of costs annually is 15% of €26,000, or €3900. The costs of travel to the jobsite for that third man are included in the calculation. Analysis of work has shown that the net productivity hardly differs when the glaziers use the improved methods, but the time spent for rests was reduced by about 10%. Presumably this is the result of a reduction of the musculoskeletal workload. It may be expected that part of that time formerly spent resting will be used to perform more work. Since a working day consists of many different tasks, including travel, management and consultants estimate that an increase in productivity of 3% is likely. This is equivalent to 3% of the margin between the turnover of two men, minus their wages. The team’s annual turnover is 1670 man-hours times two men times €35/hour, a total of €116,900. Their annual wages together are twice €26,000, or €52,000. So the margin of their work is €64,900. Therefore, the new working methods produce a gain in productivity of 3% of €64,900, or €1947 per year. The increased productivity does not mean that the workload and the discomfort will not decrease. Peak loads on the back, arms, and shoulders in particular are reduced. As a result, the related health complaints are expected to decrease, and so will the number of lost working days. The absenteeism rate in this branch of industry is 7%. From previous projects (Koningsveld and Thé 1999), we know that 45% of the absenteeism among glaziers is caused by musculoskeletal disorders, and 50% of these cases originate mostly or completely in the work. That means that 7% of 45% of 50%, or 1.58% of the work force is lost by absenteeism as a result of manual handling problems. When the workers do use the improved tools and methods frequently, the most physically straining work is eliminated, though not all of it. Therefore, it is likely that only part of the work-related absenteeism caused by musculoskeletal disorders would decrease. Ergonomists have estimated a decrease of 40%. So the decrease in absenteeism would be 40% of 1.58%, or 0.63%, with a value of €328 per year (0.63% × 2 men × €26,000 wages).

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TABLE 23.2 Financial Costs and Benefits of New Equipment for Glaziers Per year

Cash flow Investments • •

Depreciation costs Training in new working methods

Operating costs • Inspection, maintenance • Reduction of lost working days Performance: • No 3rd man needed • Increased productivity Total cash flow

€ 640 p.m.

€ 200 − € 328 − € 3,900 − € 1,947 − € 5,335

The benefits generated by productivity gains and reduced absenteeism add up to an annual total of €6175. When these benefits are compared to the annual costs of €840, we can conclude that the financial ratio is very positive. In addition, several nonfinancial benefits can be seen. Work-related discomfort is decreased and the health of the glaziers will be better over the long term, so it is more likely that they can stay active in their work. These points are important for employers, because the recruitment of new young workers is a big problem. If the workload is lighter, more people can perform the work, and recruitment can be directed at a larger target group. The risk of damage to the panes, to the frames, and to parts of the building is reduced because the carts and hoists allow better control over the handling process. The risk of cutting and falling accidents is also reduced. Table 23.2 presents the usual information given in a cash flow table. The benefits are given as negative amounts and the costs as positive amounts.

23.4

CASE 2: CLEANERS IN HOME CARE

Those who work as cleaners in home care organizations encounter several problems in their work. First, the work is not appreciated as important. Second, the cleaners have to work with the equipment and methods that happen to be available in the client’s home. The home care organizations suffer from high absenteeism rates, a high personnel turnover, low customer satisfaction, and an even lower worker satisfaction. The employers’ organizations and the employee unions decided to collaborate with the aim of improving the work. One of their proposed interventions is the development of a new set of tools and procedures for cleaning. The system is based on microfiber technology. Cloths for cleaning surfaces can be used without chemical additives and only a little water. The cleaning is done with only minor physical effort, because the cloths don’t need to be wrung out. The whole cleaning set is based on this kind of material, so mops and even feather dusters are newly designed. A specially developed bag contains all

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or most of the materials and shows that the cleaner is a professional using professional methods. All of this improves the comfort aspects of the work. Like some other important factors, the costs/benefits ratio is of major concern to the management of home care companies. The initial investment in cleaning sets is high, and the benefits cannot always be been seen easily. In close collaboration with a major supplier, management from home care organizations, ergonomists, and a costs/benefits expert, a computer model is constructed in MS Excel in order to calculate three options: • • •

The whole set of tools and cleaning cloths stays with the client. Part of the set stays with the client, but the cleaner owns a personal set of cloths and takes care of the cleaning process. The whole set belongs personally to the cleaner, who takes it to and from the client’s location. The set can be carried as a bag on the shoulder, or it can be hung on the bicycle.

Cost categories to be considered are the initial investment; replacement of cloths and tools after a specific term; training; information to workers and to clients; and costs of absenteeism. Turnover of personnel and of clients is also taken into account, and each individual home care organization can fill in its own specific data (Fig. 23.2). Benefits are calculated by reduction of the costs to replace absent workers. The company chooses out of four solutions to help solve the problems created by lost working days: • • • •

Temporary workers Overtime work Larger work force (same % as the absenteeism rate) No service to the home if a cleaner is ill

FIGURE 23.2 The input data for the costs and benefits calculation for home care cleaning.

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In addition to reducing the cost of lost working days, a 15% higher productivity rate can be reached by using the new set of cleaning tools. However, most cleaners work only a couple of hours a day and visit only two or three clients, so that productivity increase would not lead to more clients per day. Instead of a reducing the extent of the cleaners’ contracts, most home care organizations prefer to allow their cleaners to use the extra time for providing social care and attention to the client. It is proven that this helps to improve both the quality of work and the quality of service. Returning to the cleaning set options discussed earlier, results show that in most cases, option A (the whole cleaning set remains at client’s place) is too expensive. This option yields a positive ratio only if a relatively large number of hours are spent per client per week. With option B, the ratio depends mostly on the extent of the cleaner’s contractual working hours per week: Above ten hours per week the benefits exceed the costs. Option C is beneficial in almost all cases. Of course the choice of how to solve the absenteeism problem is important. Temporary workers are a costly solution, although they offer maximum flexibility. A larger workforce is cheapest, but basically not very flexible. With the computer model developed for this study, a home care company can get insight into the financial consequences of all options when considering changing the cleaning tools and procedures. The most comfortable solution for the workers is relatively costly, and it is likely to be a solution that does not completely repay the investment. Nevertheless, some companies choose that option in the belief that good working conditions are always a good investment.

23.5 CONCLUSIONS Investing in products that increase comfort or reduce discomfort can pay off. This chapter describes a method for managing professional products that is successful when applied on a variety of products. It is difficult to have the payback completely financed by sick leave reduction, and combinations with productivity increases are often more interesting (see also Chapters 5 and 7).

REFERENCES Beune, H.A.Th. (2001) “The approach of physical load in Dutch homecare.” In C.H. Nygaard, T. Luopajärvi, S. Lusa and M. Lappänen, eds., Proceedings of NES 2001: Promotion of Health through Ergonomic Working and Living Conditions (Tampere, Finland) University of Tampere, School of Public Health: 402–406. Jong, A.M. de (2002) Improving Working Condition at the Construction Site, Delft: University of Technology (Ph.D. thesis, in Dutch). Koningsveld, E.A.P. and Thé, K. (2000) “Ergonomics and economics: Dilemmas and chances.” Proceedings of the 14th Triennial Congress of the International Ergonomics Association, San Diego (on CD-ROM). Koningsveld, E.A.P. (2003) “Indicators that convince management, workers, and supporting departments.” In H. Luczak and K.J. Zink, eds., Human Factors in Organizational Design and Management, VII. Re-Designing Work and Macroergonomics—Future Perspectives and Challenges, Santa Monica: International Ergonomics Association, 753–756.

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Koningsveld, E.A.P., Dul, J,. Rhijn, J.W. van and Vink, P. (2003) “Enhancing the impact of ergonomic interventions.” In Ergonomics in the Digital Age. Proceedings of the 15th Triennial Congress of the International Ergonomics Association, Seoul (on CD-ROM). Koningsveld, E.A.P. (2003) “Costs related to working conditions in the construction industry.” In H. Strasser, K. Kluth, H. Rausch and H. Bubb, eds., Quality of Work and Products in Enterprises of the Future, Stuttgart: Ergonomia Verlag, 208–212. Koningsveld, E.A.P. and Thé, K. (1999) Macro Costs of Poor Working Conditions in the Dutch Construction Industry, Amsterdam: Elsevier (in Dutch). Koningsveld, E.A.P., Bronkhorst, R.E. and Schoenmaker, N. (2002) A Pilot Study into the Costs and Benefits of Solutions in the Field of Design for All and Disability Management, Hoofddorp: TNO Arbeid (in Dutch). Koningsveld, E.A.P., Overbosch, H. and Bronkhorst, R.E. (2003) “Costs and benefits of design for all.” In Ergonomics in the Digital Age. Proceedings of the 15th Triennial Congress of the International Ergonomics Association, Seoul (on CD-ROM). Reyneveld, K., Koningsveld, E.A.P. and Rhijn, J.W. van (2001) Costs and Benefits of Ergonomic Interventions in the Assembly Industry, Hoofddorp: TNO Work and Employment (in Dutch). Stanton, N.A., Baber, C.(2003) “Editorial: On the cost-effectiveness of ergonomics.” Applied Ergonomics, 34: 407–411. Urlings, I.J.M., Bronkhorst, R.E. and Grinten, M.P. van der (1998) “A participatory ergonomics approach to redesign working methods and tools of glaziers.” In P. Vink, E.A.P. Koningsveld and S. Dhondt, eds., Human Factors in Organizational Design and Management, IV, Amsterdam: Elsevier, 597–602.

Index A ADAPS, 202 Adjustable chair, 101 Adjustable table, 101 Airplane comfort, 4 Alstom, 239 Althoff, 148 Andersson, 148 Arbouw, 73 Arisz, 209 Armrest, 23, 164, 243, 256 Armstrong, 21 ASPA, 153 Assembly, 111, 130 Assembly Process Scheme, 119 Attebrant, 27

B Back shell, 165 Backrest, 23, 149, 164 Bag sealing, 219 Bahco Tools, 184, 190, 216 Batchwise, 128, 131 Bauer, 201 Becker, 239 Bernoux, 83 Beune, 281 Biometrics, 185 Blatter, 181 Bobjer, 184, 207 Body height, 143 Bombardier, 155 Bongers, 19, 197, 219 Borg, 211 Bosch, 219 Boussena, 214 Brambilla, 27 Bricklayers, 56 Bricklayers’ assistant, 66 Bricks raised, 59 Broersen, 194 Bronkhorst, 14, 155, 181, 240, 247 Bullinger, 199, 214 Buttock and body pressure, 34

Buurman, 196 Byström, 214

C CAD, 149 Carrasco, 219 Chaffin, 61 Chair, 35, 101, 137, 148, 170, 235 Chair elements, 23 Chair size, 142 Chao, 24, 208 Cheung, 169 Cleaning, 285 Climate, 253 Comfort and emotion, 9 Comfort in literature, 5 Comfort model, 15 Concept car, 264 Conflict, 47 Construction, 193 Controls, 173, 240, 252, 270 Cook, 181, 194 Corlett, 211 Cost/benefit, 91, 92, 281 Costs, 42 Cotton, 46 Creative Box Inc., 264 CRFiat, 114 Croney, 137

D Dainoff, 101 Dashboard, 252 Davies, 41 Definition of comfort, 14 Definition of ergonomics, 8 Definition of participatory ergonomics, 43 Dekker, 229 Delleman, 101 Design process, 51, 138 Desmet, 1, 170 Details, 247 Deursen, 129, 152

289

290

Index

Dieën, 147 Diffusion, 75 Discomfort at work, 19 Discomfort in literature, 7 Djajadiningrat, 172, 263 Docherty, 131 Dreyfuss, 196 Driver, 230, 272 Driver performance, 240 Drivers’ comfort, 239 Dul, 8, 197 Dynamic chair, 148 Dynamics in sitting, 147

Flannagan, 232 Flexed back, 90 Flexible interior, 270 Fogleman, 96 Ford, 115 FOSAG, 76 Fransson, 196 Fraser, 200 Frederiksson, 130 Fujimaki, 33 Furniture, 137 Future car, 263 Future machine, 236

E

G

Earth-moving machines, 17, 24, 229, 247 Easy-roll, 90 Ebe, 33 Egress, 160, 250 Ehn, 49 Eijnatten, 112, 130 Eikhout, 181, 199, 207 Eklund, 148 Elderly, 224 Elements of the comfort model, 16 Eleven-step program, 209 Emergency lights, 117 Emocard, 10, 171 Emotion, 9, 169, 264 End-user opinion, 27 Envisioning tools, 50 Ergomix, 51, 248 Ergonomical design, 240 Ergonomical set, 210 Ergonomics, 8 Ergoseating, 33 ergoTool, 113, 184 ETEC, 229, 259 European Foundation for the Improvement of Living and Working Conditions, 42 Excavator, 28, 230, 256 Experiental design, 264

Garner, 196 Giguère, 231 Glass cart, 78 Glass hoist, 77 Glass sledge, 78 Glaziers, 73, 283 Goniometry, 181 Goossens, 19 Graf, 148 Grammer, 252 Grandjean, 96, 172 Grinten, 129, 181, 207, 247 Groenesteijn, 111

F Faber Electronics BV, 117 Feelings, 173, 269 Feggeler, 182 Fellows, 24, 208 Finland Post, 114 FIOH, 113 Fixed chair, 174

H Hagberg, 130 Hagedoorn-de Groot, 111, 219 Haines, 51 Hales, 148 Han, 164 Hand, 24, 182, 199, 207, 225 Hand tool comfort, 24, 181, 207 Handle, 184, 242 Haperen, 263 Headrest, 164 Heat regulation, 258 Height adjustable pedals, 241 Height adjustable seats, 241 Helander, 8, 22, 172, 215 Herzberg, 20 Hildebrandt, 97 History, 16 Holbrook, 170 Home care, 285 Home furniture, 137 Hoogendoorn, 148

Index Hornyánszky, 49 Houy, 200 Hsiao, 70 Humidity, 18

I Imada, 96 Implementation, 47 Importance of comfort, 1 Inalfa Roof Systems, 51 Indirect view, 232 Ingress, 160, 250 Installation work, 85 Interior, 17, 241, 263 Interior Centre, 137 Ishihara, 9 ISO/CD 11226, 62

J JAFICA, 137 Jäger, 65 Jensen, 24 Jianghong, 24 Johansson, 126, 130 Jong, 55, 73, 85, 195, 281 Jørgensen, 66 joysticks, 257

K Kaiser AG, 229, 255 Kamijo, 33 Kansei, 9 Kapandji, 196 Karimoku, 137 Keyboard, 96 Kilbom, 62 Kishi, 33 Kittusamy, 26 Kneeling, 90 Kogi, 48 Kompier, 95 König, 193 Koningsveld, 55, 83, 194, 281 Kosuga, 137 Krause, 155, 229, 247 Kroemer, 148 Kuijt-Evers, 7, 13, 230, 248 Kuorinka, 43

291

L Land, 231 Landstra, 200 Lansbergis, 131 Lean manufacturing, 131 Lee, 263 Lifting, 61, 75, 90, 114 Local perceived discomfort, 189 Local postural discomfort, 99, 157, 211 Long Island Railroad, 167 Longneck, 235 Looze, 13, 33, 85, 111, 129, 147 Lugt, 17 Luttman, 65

M Macfarlane, 219 Macromovements, 175 Manenica, 214 Manual bag sealing, 219 Manufacturing, 112 Marinissen, 195 Markers, 150 Marras, 20 MAS, 119 Mathiassen, 112, 151 MAWP, 132 McGorry, 208 Meijer, 66 Mekhora, 96 Merllié, 2 Metal clip, 221 Miedema, 56 Mirror, 254 Mital, 62 Mitsuya, 137 Mock-up, 51, 202, 241 Modification, 156 Molen, 61, 73 Molenbroek, 140, 164, 200 Mortar raised, 59 Movement, 19 Multina, 167 Musculoskeletal problems, 2

N Nagamachi, 9 Nakada, 27 NF X 35–106, 62 Nichols, 41

292 NIOSH, 62 Nissan, 263 Noise, 18, 254, 259 Noro, 33, 44, 96, 137, 248

O Office work, 96 Ólafsdóttir, 126 Oliver, 248 Ong, 96, 172 Operator, 118, 232 Opinion of experts, 44 Osinga, 239 Östman, 49 Overbeeke, 1, 169, 263

Index

R Radwin, 196 Rebar tying, 194 Reflection, 231 Reijneveld, 247, 181 RET, 239 Reynolds, 164 Rhijn, 111, 129, 182 Richards, 14 Ridder, 79 Roetting, 230 Rogers, 82, 92 Roozenburg, 195 Ruiter, 193 Russell, 10

S P Paint scraper, 181 Painters, 181 Palacios, 42 Parenmark, 126 Park, 33 Participants, 45, 118 Participating groups, 45 Participation, 42 Participatory design, 51, 207 Participatory ergonomics, 8, 41 Passenger seat, 155 Patry, 46 Paus GmbH, 229, 249 Pedals, 241, 256 Pelvis angle, 36 Philips DAP, 131 Picking, 132 Placing, 132 Ploeger, 194 Polling, 208 Posture, 19 prEmo, 10 prEN 1005-4, 62 Pressure, 19, 33 Pressure distribution, 37, 143 Preventing discomfort, 19 Problem identification, 46 Production concept, 122 Production line, 130 Productivity, 112, 132, 215, 285 Proper, 2, 19 Prototype, 165, 244 PSIM, 113

Safety, 225 Salary records, 96 Sauter, 112 Schifferstein , 19 Schoenmaker, 129 Schön, 49 Screwdriver, 207 Seat, 155, 235, 243, 250 Seat comfort, 20, 33 Seat pan, 23 Seating clinic, 139 Sector, 75 Self-chosen, 102 Serber, 148 Shop assistants, 223 Sick leave, 70 Sitting behavior, 157 Slater, 14 Smallwood, 194 Smell, 18 Smets, 9 Smulders, 147 Solution choice, 46 Sonneveld, 19 Spinal shrinkage, 151 Stadiometer, 150 Stakeholders, 42 Stanton, 281 State, 17 Static chair, 152 Steelcase, 42 Steel-fixing tool, 193 Steering column, 251 Stoeckli, 48 Street car, 239 Suzuki, 148

Index

T Table height, 106 Tape, 221 Temperature, 18 Tereoka, 137 Thackara, 208 Theimer, 18 Theory on comfort, 14 Tola, 27 Tool, 184, 196 Touch, 19 Train seat, 155 Tram, 239 Tram driver, 239 Transporter, 276 Transporting bricks, 66 Tuinzaad, 51, 111 Twin Seal, 220 Tying tool, 195 TyTecker, 194

U

293 Virtual reality, 49 Visibility, 233 Visser, 193, 229 Visual input, 17 Volvo Car Corperation, 114 Vormer, 229

W Wakula, 194 Waters, 62, 121 Wensveen, 173 Wheel barrow, 68 Wheel loader, 28 Wilder, 24 Wilke, 148 Wilson, 43, 83, 240 Window, 231, 257, 272 Winkel, 21, 126 Woodson, 196 Word processing, 149 Workplace design, 133 Workbench, 88

Urlings, 75, 87, 283

V

Y

Vahtera, 126, 131 VDU screen, 98 Vedder, 231 Vehicle interior comfort, 24 Vents, 253 Verbeek, 101, 172 Vergare, 24 Vibration, 26, 230, 242, 248 View, 231, 240

Yamada, 111 Yamatake, 115

Z Zhang, 7, 21 Zhao, 164 Zimmerman, 27