Ergonomics The human factor A practical approach to work systems design

Transcription

1 SAA HB Handbook Ergonomics The human factor A practical approach to work systems design

2 SAA HB Handbook Ergonomics The human factor A practical approach to work systems design First published as part of SAA MH Revised and redesignated in part as SAA HB PUBLISHED BY STANDARDS AUSTRALIA (STANDARDS ASSOCIATION OF AUSTRALIA) 1 THE CRESCENT, HOMEBUSH, NSW 2140 ISBN

3 SAA HB PREFACE This Handbook has been prepared as a basic guide to the subject of ergonomics. It is not intended for use as a definitive reference source, since a number of excellent texts on the subject have already been published. However, for those who do not need to acquire a more comprehensive treatment, this handbook will prove useful. Ergonomics is a design philosophy which studies the three-way interactions between people, the equipment they use at their workplaces, and the environment within which the people, and equipment are placed. Its object is to design both the workplace and the environment in such a way that the most efficient use is made of human capabilities, without exceeding human capacities. To fully understand the limitations of the human body, ergonomists need to have a working knowledge of anatomy, the ability to perceive the forces at work on the body, and a knowledge of the psychological, as well as the physiological, needs of the individual within a work system. The practitioners of ergonomics come from a wide variety of backgrounds the sciences, engineering, medicine, and psychology. The subject forms the basis (or at least a part) of an increasing number of courses available within a number of colleges and universities across Australia, and indeed the world. Appendix A lists the documents referred to in this Handbook together with related documents for further reading. Copyright STANDARDS AUSTRALIA Users of Standards are reminded that copyright subsists in all Standards Australia publications and software. Except where the Copyright Act allows and except where provided for below no publications or software produced by Standards Australia may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from Standards Australia. Permission may be conditional on an appropriate royalty payment. Requests for permission and information on commercial software royalties should be directed to the head office of Standards Australia. Standards Australia will permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively in-house by purchasers of the Standard without payment of a royalty or advice to Standards Australia. Standards Australia will also permit the inclusion of its copyright material in computer software programs for no royalty payment provided such programs are used exclusively in-house by the creators of the programs. Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended or revised. The number and date of the Standard should therefore be clearly identified. The use of material in print form or in computer software programs to be used commercially, with or without payment, or in commercial contracts is subject to the payment of a royalty. This policy may be varied by Standards Australia at any time.

4 3 SAA HB CONTENTS Page FOREWORD... 5 SECTION 1 HUMAN PHYSICAL CAPABILITIES ANTHROPOMETRY... 6 BIOMECHANICS MUSCULOSKELETALSYSTEM Skeletalsystem Muscularsystem Muscleenergysources Staticmusclefatigue Dynamicmusclefatigue REACHENVELOPES Staticreachenvelopes Dynamicreachenvelopes Clearances Strength SECTION 2 PHYSIOLOGICAL FACTORS DISPLAYSANDCONTROLS Designofdisplaysandcontrols DISPLAYS Analoguedisplays Scaledivisions Scaledesign Numeralheight Pointerposition Digitaldisplays Colour Sizeofdisplay Advantages ofdigitaldisplays Disadvantages ofdigitaldisplays OTHERFORMSOFDISPLAY CONTROLS Continuous controls Discretecontrols Toggleswitches Rockerswitches Rotaryswitchesandknobs Push-buttons Feedback Illuminatedpush-buttons Markingsonpush-buttons Indicatorlights... 35

5 SAA HB Page CONTROLIDENTIFICATION Colourcoding Shapecoding Sizecoding Labelling STEREOTYPES PANELDESIGNANDCONTROLIDENTIFICATION THEEYEANDVISION Anatomyoftheeye Visualfield Accommodation Glare Relativeglare Absoluteglare Adaptiveglare Humidity LIGHTING THEEAR,HEARINGANDNOISE Noise Anatomyoftheear Dailynoisedose(DND) Effectsonperformance VIBRATION Whole-bodyvibration Part-bodyvibration Vibrationreductiontechniques THERMALENVIRONMENT SECTION 3 WORK ORGANISATIONAL FACTORS INTRODUCTION RESISTANCETOCHANGE CONSULTATION MULTISKILLING PACEDSYSTEMSOFWORK TIMEMAXIMIZATION OPERATORAUTONOMY SYSTEMSAPPROACH MANAGEMENTSTYLES SECTION 4 APPLIED ERGONOMIC EXAMPLES WORKPLACEDESIGN OFFICEENVIRONMENT APPENDIX A LIST OF REFERENCED AND RELATED DOCUMENTS

6 5 SAA HB FOREWORD Ergonomics is a science which developed from the need to understand the physiological, psychological and social needs of operators during the process of designing work environments. These requirements must be understood by the designer while developing the brief for the product or facility under consideration, since failure to take these human factors into consideration during the design phase can create unforeseen errors when the product or system is used. Historically, engineers, architects and designers have tended to assess the suitability of their designs against their own experiences and expectations, only to find that once the design is implemented, many users employ different criteria for assessment and a variety of unforeseen problems with the product have arisen. In the majority of cases, these oversights or errors will cause annoyance to the operator. However, in complex systems, the results may be disastrous. The word ergonomics, first used in 1949, is derived from two Greek words, ergon meaning work, and nomos meaning natural laws. Thus, ergonomics means the natural laws relating to work. Ergonomics can be seen by some as being as much an art as it is a science due to the many subtle differences which individuals bring to their working environment. Concentration on the physical capabilities and needs of the population tends to oversimplify these needs as being an extension of the engineering model to product design. The various shapes and sizes of the population (anthropometry) together with the strength and power of the human musculoskeletal system (biomechanics) provide an engineering basis for assessing design suitability. The cognitive or information processing capabilities of people influences their decisionmaking processes as well as their abilities to understand and interpret information provided to them. Related to this information processing capability, ergonomics provides data and guidance on the capabilities of human visual and auditory systems. The design and development of computer software has been a growth area for ergonomics during the 1980s in recognition of the significant influence that computer instructions and commands have on the abilities of users to learn and operate the multitude of computer systems now available. The assessment of computer software, or information technology, is one of the main areas of current ergonomic research. Other areas of research include the evaluation of the body s sensitivity to variations in the thermal environment as well as the effects of either localised or whole-body vibration. Ergonomics provides a recognition of the context where the users of the work environment are likely to be influenced by the overall work system and organisation over their tasks. Most tasks performed by users are within an environment consisting of a social interaction with work peers, coupled with a management structure to provide guidance on the work practices and work organisation within which constraints their tasks are performed. The influence of the performance requirements, involving both the quantity and quality of output expected, also influences the capabilities of the user to meet the system demands. The macro-ergonomic study involving work organisation is a major element in understanding human performance capabilities within their working environment. Within a group of people involved in performing work, individual differences, including personality type, ability to cope with stress, fatigue and motivation, will be present and will determine the ability of each individual to maintain consistent output to meet the set performance requirements. The ability of supervisors and managers to account for these needs will generally have as great an impact on the efficiency of their system as will the physical capabilities of the staff. The challenge in ergonomics in the 1990s is to provide a balanced input in a holistic concept of the needs of people within their work environments. To optimise the efficiency of the human element within a man-machine system, which includes the reduction of injury risks, remains the current primary focus of ergonomics in Australia.

7 SAA HB SECTION 1 HUMAN PHYSICAL CAPABILITIES ANTHROPOMETRY Anthropometry is the science which deals with the size and shape of people within a population. The population may be of any size, numerically, though the normal and natural meaning of population would indicate the population of a particular country. A number of countries in the world, including the United States of America, Germany, United Kingdom and Japan, have sampled sufficient numbers of their respective populations to have developed a national anthropometric profile. Australia has not yet developed such a database, hence uses elements of the American or European database as a guide. A number of studies in Australia, including those carried out by both the coal industry and the automotive industry in 1991, indicates that direct dependence on overseas anthropometric data can be misleading to the designer because of Australia s cosmopolitan population. Hence, these data should only be used as a guide. When designing for an adult population, a number of questions must be answered prior to using these databases. These questions include the following: (a) Are the users both male and female? The answer to this question is generally Yes. With increased multi-skilling in the workplace and affirmative action programs, a cross-section of the adult population, regardless of gender, is generally found. (b) Who is in the user population? In the manufacturing industry, it is often found that particular ethnic groups congregate onto particular shifts. Hence, the anthropometric profile of a company may differ between shifts as well as between cities where particular ethnic groups may live. (c) Which group within the population will be placed at the greatest disadvantage by the design? For example, the tallest will hit their head; shortest cannot reach; overweight won t fit; and left-handers cannot operate systems. An objective of ergonomics is not to design for the average person (who does not exist), but for the majority of the user population, typically 90 percent. Special arrangements are often required for those at the extreme ends of the population, i.e. the very small or very large. (d) Which are the critical anthropometric dimensions? Table 1 provides a range of anthropometric dimensions for the 5th, 50th and 95th percentiles of British adults and Figure 1 shows the positions on the body to which the data in Table 1 refers. For example, bench heights refer to standing elbow height (Item 6), seat height refers to popliteal height (Item 18), while machine guarding refers to finger, hand and arm dimensions (Items 25-42), as appropriate. Ergonomists tend to design workplaces that will suit the majority of users from nearly the smallest to nearly the largest. Typically, this would cover the range from the 5th percentile to the 95th percentile of the user population. People who fall outside this range, usually require special arrangements. Where the workforce or population includes both male and female members, as will most often be the case, the range will typically encompass the 5th percentile female to the 95th percentile male. One must, however, be alert and ensure that this is the case. The design may require adjustability, if the task requires it, or the use of standardised dimensions with consideration of the groups at greatest disadvantage. COPYRIGHT

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