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Designing for Everyone
In designing a product or an industrial process, one focuses on the “average” and “healthy” worker. Information regarding human abilities in terms of muscular strength, bodily flexibility, length of reach, and many other characteristics is for the most part derived from empirical studies carried out by military recruitment agencies, and reflects measured values valid for the typical young male in his twenties. But working populations, to be sure, consist of people of both sexes and a broad range of ages, to say nothing of a variety of physical types and abilities, levels of fitness and health, and functional capacities. A classification of the varieties of functional limitation among people as outlined by the World Health Organization is given in the accompanying article "Case Study: The International Classifcation of Functional Limitation in People." At present, industrial design for the most part takes insufficient account of the general abilities (or inabilities, for that matter) of workers at large, and should take as its point of departure a broader human average as a basis for design. Clearly, a suitable physical load for a 20-year-old may exceed the capacity to manage of a 15-year-old or a 60-year-old. It is the business of the designer to consider such differences not only from the point of view of efficiency, but with a eye to the prevention of job-related injury and illness.
The progress of technology has brought about the state of affairs that, of all the workplaces in Europe and North America, 60% involve the seated position. The physical load in work situations is now on average far less than before, but many worksites, nonetheless, call for physical loads that cannot be sufficiently reduced to fit human physical capabilities; in some developing countries, the resources of current technology are simply not available to relieve the human physical burden to any appreciable extent. And in technologically advanced countries, it is still a common problem that a designer will adapt his or her approach to constraints imposed by product specifications or production processes, either slighting or leaving out human factors related to disability and the prevention of harm due to the workload. With respect to these aims, designers have to be educated to devote attention to all such human factors, expressing the results of their study in a product requirements document (PRD). The PRD contains the system of demands which the designer has to meet in order to achieve both the expected product quality level and the satisfaction of human capability needs in the production process. While it is unrealistic to demand a product that matches a PRD in every respect, given the need of unavoidable compromises, the design method suited to the closest approach to this goal is the system ergonomic design (SED) method, to be discussed following a consideration of two alternative design approaches.
This design approach is characteristic of artists and others involved in the production of work of a high order of originality. The essence of this design process is that a concept is worked out intuitively and through “inspiration”, allowing problems to be dealt with as they arise, without conscious deliberation beforehand. Sometimes, the outcome will not resemble the initial concept, but nonetheless represents what the creator regards as his or her authentic product. Not seldom, too, the design is a failure. Figure 1 illustrates the route of creative design.
Figure 1. Creative design
System design arose from the need to predetermine the steps in design in a logical order. As design becomes complex, it has to be subdivided into subtasks. Designers or subtask teams thus become interdependent, and design becomes the job of a design team rather than an individual designer. Complementary expertise is distributed through the team, and design assumes an interdisciplinary character.
System design is oriented to the optimal realization of complex and well-defined product functions through the selection of the most appropriate technology; it is costly, but the risks of failure are considerably reduced as compared with less organized approaches. The efficacy of the design is measured against the goals formulated in the PRD.
The way in which the specifications formulated in the PRD are of the first importance. Figure 2 illustrates the relationship between the PRD and other parts of the system design process.
Figure 2. System design
As this scheme shows, the input of the user is neglected. Only at the end of the design process can the user criticize the design. This is unhelpful to both producer and user, since one has to wait for the next design cycle (if there is one) before errors can be corrected and modifications made. Furthermore, user feedback is seldom systematized and imported into a new PRD as a design influence.
System ergonomic design (SED)
SED is a version of system design adapted to ensure that the human factor is accounted for in the design process. Figure 3 illustrates the flow of user input into the PRD.
Figure 3. System ergonomic design
In system ergonomic design, the human being is considered part of the system: design specification changes are, in fact, made in consideration of the worker’s abilities with respect to cognitive, physical and mental aspects, and the method lends itself as an efficient design approach for any technical system where human operators are employed.
For example, to examine the implications of the worker’s physical abilities, task-allocation in the design of the process will call for a careful selection of tasks to be performed by the human operator or by the machine, each task being studied for its aptness to machine or human treatment. Clearly, the human worker will be more effective at interpreting incomplete information; machines however calculate much more rapidly with prepared data; a machine is the choice for lifting heavy loads; and so forth. Furthermore, since the user-machine interface can be tested at the prototype phase, one can eliminate design errors that would otherwise untimely manifest themselves at the phase of technical functioning.
Methods in User Research
No “best” method exists, nor any source of formulae and sure and certain guidelines, according to which design for disabled workers ought to be undertaken. It is a rather a common-sense business of making as exhaustive search of all obtainable knowledge relevant to the problem and of implementing it to its most evident best effect.
Information can be assembled from sources such as the following:
The methods described above are some of the various ways of gathering data about people. Methods exist, too, to evaluate user-machine systems. One of these—simulation—is to construct a realistic physical copy. The development of a more or less abstract symbolic representation of a system is an example of modelling. Such expedients, of course, are both useful and necessary when the actual system or product is not in existence or not accessible to experimental manipulation. Simulation is more often used for training purposes and modelling for research. A mock-up is a full-size, three-dimensional copy of the designed workplace composed, where necessary, of improvised materials, and is of great use in testing design possibilities with the proposed disabled worker: in fact, the majority of design problems can be identified with the aid of such a device. Another advantage to this approach is that the motivation of the worker grows as he or she participates in the design of his or her own future workstation.
Analysis of Tasks
In the analysis of tasks, different aspects of a defined job are subject to analytical observation. These manifold aspects include posture, routing of work manipulations, interactions with other workers, handling tools and operating machines, the logical order of subtasks, the efficiency of operations, static conditions (a worker may have to perform tasks in the same posture over a long time or with high frequency), dynamic conditions (calling for numerous varying physical conditions), material environmental conditions (as in a cold slaughterhouse) or non-material conditions (as with stressful work surroundings or the organization of the work itself).
Work design for the disabled person has, then, to be founded on a thorough task analysis as well as a full examination of the functional abilities of the disabled person. The basic design approach is a crucial issue: it is more efficient to elaborate all possible solutions for the problem in hand without prejudice than to produce a single design concept or a limited number of concepts. In design terminology, this approach is called making a morphological overview. Given the multiplicity of original design concepts, one can proceed to an analysis of the pro and con features of each possibility with respect to material use, construction method, technical production features, ease of manipulation, and so on. It is not unprecedented that more than one solution reaches the prototype stage and that a final decision is made at a relatively late phase in the design process.
Although this may seem a time-consuming way to realize design projects, in fact the extra work it entails is compensated for in terms of fewer problems encountered in the developmental stage, to say nothing that the result—a new workstation or product—will have embodied a better balance between the needs of the disabled worker and the exigencies of the working environment. Unfortunately, the latter benefit rarely if ever reaches the designer in terms of feedback.
Product Requirements Document (PRD) and Disability
After all information relating to a product has been assembled, it should be transformed into a description not only of the product but of all those demands which may be made of it, regardless of source or nature. These demands may of course be divided along various lines. The PRD should include demands relating to user-operator data (physical measurements, range of motion, range of muscular strength, etc.), technical data (materials, construction, production technique, safety standards, etc.), and even conclusions arising out of market feasibility studies.
The PRD forms the designer’s framework, and some designers regard it as an unwelcome restriction of their creativity rather than as a salutary challenge. In view of the difficulties at times accompanying the execution of a PRD, it should always be borne steadily in mind that a design failure causes distress for the disabled person, who may relinquish his or her efforts to succeed in the employment arena (or else fall helpless victim to the progress of the disabling condition), and additional costs for redesign as well. To this end, technical designers should not operate alone in their design work for the disabled, but should cooperate with whatever disciplines are needed for securing the medical and functional information to set up an integrated PRD as a framework for the design.
When a prototype is built, it should be tested for errors. Error testing should be carried out not only from the point of view of the technical system and subsystems, but also with a view to its usability in combination with the user. When the user is a disabled person, extra precautions have to be taken. An error to which an unimpaired worker may successfully respond in safety may not afford the disabled worker the opportunity of avoiding harm.
Prototype testing should be carried out on a small number of disabled workers (except in the case of a unique design) according to a protocol matched to the PRD. Only by such empirical testing can the degree to which the design meets the demands of the PRD be adequately judged. Although results on small numbers of subjects may not be generalizable to all cases, they do supply valuable information for the designer’s use in either the final design or in future designs.
The evaluation of a technical system (a work situation, machine or tool) should be judged on its PRD, not by questioning the user or even by attempting comparisons of alternative designs with respect to physical performance. For instance, the designer of a specific knee brace, basing his or her design on research results that show unstable knee joints to exhibit a delayed hamstring reaction, will create a product that compensates for this delay. But another brace may have different design aims. Yet present evaluation methods show no insight as to when to prescribe what kind of knee brace to which patients under what conditions—precisely the sort of insight a health professional needs when prescribing technical aids in the treatment of disabilities.
Current research aims at making this sort of insight possible. A model used to obtain insight into those factors which actually determine whether or not a technical aid ought to be used, or whether or not a worksite is well designed and equipped for the disabled worker is the Rehabilitation Technology Useability Model (RTUM). The RTUM model offers a framework to use in evaluations of existing products, tools or machines, but can also be used in combination with the design process as shown in figure 4.
Figure 4. Rehabilitation Technology Useability Model (RTUM) in combination with the system ergonomic design approach
Evaluations of existing products reveal that as regards technical aids and worksites, the quality of PRDs is very poor. At some times, the product requirements are not recorded properly; at others they are not developed to a useful extent. Designers simply must learn to start documenting their product requirements, including those relevant to disabled users. Note that, as figure 4 shows, RTUM, in conjunction with SED, offers a framework that includes the requirements of disabled users. Agencies responsible for prescribing products for their users must request industry to evaluate those products before marketing them, a task in essence impossible in the absence of product requirement specifications; figure 4 also shows how provision can be made to ensure that the end result can be evaluated as it should (on a PRD) with the help of the disabled person or group for whom the product is intended. It is up to national health organizations to stimulate designers to abide by such design standards and to formulate appropriate regulations.
Culture and technology are interdependent. While culture is indeed an important aspect in technology design, development and utilization, the relationship between culture and technology is, however, extremely complex. It needs to be analysed from several perspectives in order to be considered in the design and application of technology. Based on his work in Zambia, Kingsley (1983) divides technological adaptation into changes and adjustments at three levels: that of the individual, of the social organization and of the cultural value system of the society. Each level possesses strong cultural dimensions which require special design considerations.
At the same time, technology itself is an inseparable part of culture. It is built, wholly or in part, around the cultural values of a particular society. And as part of culture, technology becomes an expression of that society’s way of life and thinking. Thus, in order for technology to be accepted, utilized and acknowledged by a society as its own, it must be congruent to the overall image of that society’s culture. Technology must complement culture, not antagonize it.
This article will deal with some of the intricacies concerning cultural considerations in technology designs, examining the current issues and problems, as well as the prevailing concepts and principles, and how they can be applied.
Definition of Culture
The definition of the term culture has been debated at length amongst sociologists and anthropologists for many decades. Culture can be defined in many terms. Kroeber and Kluckhohn (1952) reviewed over a hundred definitions of culture. Williams (1976) mentioned culture as one of the most complicated words in the English language. Culture has even been defined as the entire way of life of people. As such, it includes their technology and material artefacts—anything one would need to know to become a functioning member of the society (Geertz 1973). It may even be described as “publicly available symbolic forms through which people experience and express meaning” (Keesing 1974). Summing it up, Elzinga and Jamison (1981) put it aptly when they said that “the word culture has different meanings in different intellectual disciplines and systems of thought”.
Technology: Part and Product of Culture
Technology can be considered both as part of culture and its product. More than 60 years ago the noted sociologist Malinowsky included technology as part of the culture and gave the following definition: “culture comprises inherited artefacts, goods, technical processes, ideas, habits and values.” Later, Leach (1965) considered technology as a cultural product and mentioned “artefacts, goods and technical processes” as “products of culture”.
In the technological realm, “culture” as an important issue in the design, development and utilization of technical products or systems has been largely neglected by many suppliers as well as receivers of technology. One major reason for this neglect is the absence of basic information on cultural differences.
In the past, technological changes have led to significant changes in social life and organization and in people’s value systems. Industrialization has made deep and enduring changes in the traditional lifestyles of many previously agricultural societies since such lifestyles were largely regarded as incompatible with the way industrial work should be organized. In situations of large cultural diversity, this has led to various negative socio-economic outcomes (Shahnavaz 1991). It is now a well-established fact that simply to impose a technology on a society and believe that it will be absorbed and utilized through extensive training is wishful thinking (Martin et al. 1991).
It is the responsibility of the technology designer to consider the direct and indirect effects of the culture and to make the product compatible with the cultural value system of the user and with its intended operating environment.
The impact of technology for many “industrially developing countries” (IDCs) has been much more than improvement in efficiency. Industrialization was not just modernization of the production and service sectors, but to some extent Westernization of the society. Technology transfer is, thus, also cultural transfer.
Culture, in addition to religion, tradition and language, which are important parameters for technology design and utilization, encompasses other aspects, such as specific attitudes towards certain products and tasks, rules of appropriate behaviour, rules of etiquette, taboos, habits and customs. All these must be equally considered for optimum design.
It is said that people are also products of their distinctive cultures. Nevertheless, the fact remains that world cultures are very much interwoven due to human migration throughout history. It is small wonder that there exist more cultural than national variations in the world. Nevertheless, some very broad distinctions can be made regarding societal, organizational and professional culture-based differences that could influence design in general.
Constraining Influences of Culture
There is very little information on both theoretical and empirical analyses of the constraining influences of culture on technology and how this issue should be incorporated in the design of hardware and software technology. Even though the influence of culture on technology has been recognized (Shahnavaz 1991; Abeysekera, Shahnavaz and Chapman 1990; Alvares 1980; Baranson 1969), very little information is available on the theoretical analysis of cultural differences with regard to technology design and utilization. There are even fewer empirical studies that quantify the importance of cultural variations and provide recommendations on how cultural factors should be considered in the design of product or system (Kedia and Bhagat 1988). Nevertheless, culture and technology can still be studied with some degree of clarity when viewed from different sociological viewpoints.
Culture and Technology: Compatibility and Preference
Proper application of a technology depends, to a large extent, on the compatibility of the user’s culture with the design specifications. Compatibility must exist at all levels of culture—at the societal, organizational and professional levels. In turn, cultural compatibility can have strong influence on a people’s preferences and aptness to utilize a technology. This question involves preferences relating to a product or system; to concepts of productivity and relative efficiency; to change, achievement and authority; as well as to the manner of technology utilization. Cultural values can thus affect people’s willingness and ability to select, to use and to control technology. They have to be compatible in order to be preferred.
As all technologies are inevitably associated with sociocultural values, the cultural receptivity of the society is a very important issue for the proper functioning of a given technological design (Hosni 1988). National or societal culture, which contributes to the formation of a collective mental model of people, influences the entire process of technology design and application, which ranges from planning, goal setting and defining design specifications, to production, management and maintenance systems, training and evaluation. Technology design of both hardware and software should, therefore, reflect society-based cultural variations for maximum benefit. However, defining such society-based cultural factors for consideration in the design of technology is a very complicated task. Hofstede (1980) has proposed four dimensional framework variations of national-based culture.
Glenn and Glenn (1981) have also distinguished between “abstractive” and “associative” tendencies in a given national culture. It is argued that when people of an associative culture (like those from Asia) approach a cognitive problem, they put more emphasis on context, adapt a global thinking approach and try to utilize association among various events. Whereas in the Western societies, a more abstractive culture of rational thinking predominates. Based on these cultural dimensions, Kedia and Bhagat (1988) have developed a conceptual model for understanding cultural constraints on technology transfer. They have developed various descriptive “propositions” which provide information on different countries’ cultural variations and their receptivity with regard to technology. Certainly many cultures are moderately inclined to one or the other of these categories and contain some mixed features.
Consumers’ as well as producers’ perspectives upon technological design and utilization are directly influenced by the societal culture. Product safety standards for safeguarding consumers as well as work-environment regulations, inspection and enforcement systems for protecting the producers are to a large extent the reflection of the societal culture and value system.
A company’s organization, its structure, value system, function, behaviour, and so on, are largely cultural products of the society in which it operates. This means that what happens within an organization is mostly a direct reflection of what is happening in the outside society (Hofstede 1983). The prevailing organizations of many companies operating in the IDCs are influenced both by the characteristics of the technology producer country as well as those of the technology recipient environment. However, the reflection of the societal culture in a given organization can vary. Organizations interpret the society in terms of their own culture, and their degree of control depends, among other factors, on the modes of technology transfer.
Given the changing nature of organization today, plus a multicultural, diverse workforce, adapting a proper organizational programme is more important than ever before to a successful operation (an example of a workforce diversity management programme is described in Solomon (1989)).
People belonging to a certain professional category may use a piece of technology in a specific fashion. Wikström et al. (1991), in a project aimed to develop hand tools, have noted that despite the designers’ assumption of how plate shares are to be held and used (i.e., with a forward holding grip and the tool moving away from one’s own body), the professional tinsmiths were holding and using the plate share in a reversed manner, as shown in figure 1. They concluded that tools should be studied in the actual field conditions of the user population itself in order to acquire relevant information on the tools characteristics.
Figure 1. The use of plate share tools by professional tinsmiths in practice (the reversed grip)
Using Cultural Features for Optimum Design
As implied by the foregoing considerations, culture provides identity and confidence. It forms opinions about the objectives and characteristics of a “human-technology system” and how it should operate in a given environment. And in any culture, there are always some features that are valuable with regard to technological progress. If these features are considered in the design of software and hardware technology, they can act as the driving force for technology absorption in the society. One good example is the culture of some southeast Asian countries largely influenced by Confucianism and Buddhism. The former emphasizes, among other things, learning and loyalty, and considers it a virtue to be able to absorb new concepts. The latter teaches the importance of harmony and respect for fellow human beings. It is said that these unique cultural features have contributed to the provision of the right environment for the absorption and implementation of advanced hardware and organizational technology furnished by the Japanese (Matthews 1982).
A clever strategy would thus make the best use of the positive features of a society’s culture in promoting ergonomic ideas and principles. According to McWhinney (1990) “the events, to be understood and thus used effectively in projection, must be embedded in stories. One must go to varying depths to unleash founding energy, to free society or organization from inhibiting traits, to find the paths along which it might naturally flow. . . . Neither planning nor change can be effective without embedding it consciously in a narrative.”
A good example of cultural appreciation in designing management strategy is the implementation of the “seven tools” technique for quality assurance in Japan. The “seven tools” are the minimum weapons a samurai warrior had to carry with him whenever he went out to fight. The pioneers of “quality control circles”, adapting their nine recommendations to a Japanese setting, reduced this number in order to take advantage of a familiar term—“the seven tools”—so as to encourage the involvement of all employees in their quality work strategy (Lillrank and Kano 1989).
However, other cultural features may not be beneficial to technological development. Discrimination against women, the strict observation of a caste system, racial or other prejudice, or considering some tasks as degrading, are a few examples that can have a negative influence on technology development. In some traditional cultures, men are expected to be the primary wage-earners. They become accustomed to regarding the role of women as equal employees, not to mention as supervisors, with insensitivity or even hostility. Withholding equal employment opportunity from women and questioning the legitimacy of women’s authority is not appropriate to the current needs of organizations, which require optimum utilization of human resources.
With regard to task design and job content, some cultures consider tasks like manual labour and service as degrading. This may be attributed to past experiences linked to colonial times regarding “master-slave relationships”. In some other cultures, strong biases exist against tasks or occupations associated with “dirty hands”. These attitudes are also reflected in lower-than-average pay scales for these occupations. In turn, these have contributed to shortages of technicians or inadequate maintenance resources (Sinaiko 1975).
Since it usually takes many generations to change cultural values with respect to a new technology, it would be more cost-effective to fit the technology to the technology recipient’s culture, taking cultural differences into consideration in the design of hardware and software.
Cultural Considerations in Product and System Designing
By now it is obvious that technology consists both of hardware and software. Hardware components include capital and intermediary goods, such as industrial products, machinery, equipment, buildings, workplaces and physical layouts, most of which chiefly concern the micro-ergonomics domain. Software pertains to programming and planning, management and organizational techniques, administration, maintenance, training and education, documentation and services. All these concerns fall under the heading of macro-ergonomics.
A few examples of cultural influences that require special design consideration from the micro- and macro-ergonomic point of view are given below.
Micro-ergonomics is concerned with the design of a product or system with the objective of creating a “usable” user-machine-environment interface. The major concept of product design is usability. This concept involves not only the functionality and reliability of the product, but issues of safety, comfort and enjoyment as well.
The user’s internal model (i.e., his or her cognitive or mental model) plays an important role in usability design. To operate or control a system efficiently and safely, the user must have an accurate representative cognitive model of the system in use. Wisner (1983) has stated that “industrialization would thus more or less require a new kind of mental model.” In this view, formal education and technical training, experience as well as culture are important factors in determining the formation of an adequate cognitive model.
Meshkati (1989), in studying the micro- and macro-ergonomic factors of the 1984 Union Carbide Bhopal accident, highlighted the importance of culture on the Indian operators’ inadequate mental model of the plant operation. He stated that part of the problem may have been due to “the performance of poorly trained Third World operators using advanced technological systems designed by other humans with much different educational backgrounds, as well as cultural and psychosocial attributes.” Indeed, many design usability aspects at the micro-interface level are influenced by the user’s culture. Careful analyses of the user’s perception, behaviour and preferences would lead to a better understanding of the user’s needs and requirements for designing a product or system that is both effective and acceptable.
Some of these culture-related micro-ergonomic aspects are the following:
The term macro-ergonomics refers to the design of software technology. It concerns the proper design of organizations and management systems. Evidence exists showing that because of differences in culture, sociopolitical conditions and educational levels, many successful managerial and organizational methods developed in industrialized countries cannot be successfully applied to developing countries (Negandhi 1975). In most IDCs, an organizational hierarchy characterized by a down-flow of authority structure within the organization is a common practice. It has little concern for Western values such as democracy or power sharing in decision-making, which are regarded as key issues in modern management, being essential for proper utilization of human resources as regards intelligence, creativity, problem solving potential and ingenuity.
The feudal system of social hierarchy and its value system are also widely practised in most industrial workplaces in the developing countries. These make a participatory management approach (which is essential for the new production mode of flexible specialization and the motivation of the workforce) a difficult endeavour. However, there are reports confirming the desirability of introducing autonomous work systems even in these cultures Ketchum 1984).
Zhang and Tyler (1990), in a case study related to the successful establishment of a modern telephone cable production facility in China supplied by a US firm (the Essex Company) stated that “both parties realize, however, that the direct application of American or Essex management practices was not always practical nor desirable due to cultural, philosophical, and political differences. Thus the information and instructions provided by Essex was often modified by the Chinese partner to be compatible with the conditions existing in China.” They also argued that the key to their success, despite cultural, economic and political differences, was both parties’ dedication and commitment to a common goal as well as the mutual respect, trust, and friendship which transcended any differences between them.
Design of shift and work schedules are other examples of work organization. In most IDCs there are certain sociocultural problems associated with shift work. These include poor general living and housing conditions, lack of support services, a noisy home environment and other factors, which require the design of special shift programmes. Furthermore, for female workers, a working day is usually much longer than eight hours; it consists of not only the actual time spent working, but also the time spent on travelling, working at home and taking care of children and elderly relatives. In view of the prevailing culture, shift and other work design requires special work-rest schedules for effective operation.
Flexibility in work schedules to allow cultural variances such as an after-lunch nap for Chinese workers and religious activities for Muslims are further cultural aspects of work organization. In the Islamic culture, people are required to break from work a few times a day to pray, and to fast for one month each year from sunrise to sunset. All these cultural constraints require special work organizational considerations.
Thus, many macro-ergonomic design features are closely influenced by culture. These features should be considered in the design of software systems for effective operation.
Conclusion: Cultural Differences in Design
Designing a usable product or system is not an easy task. There exists no absolute quality of suitability. It is the designer’s task to create an optimum and harmonic interaction between the four basic components of the human-technology system: the user, the task, the technological system and the operating environment. A system may be fully usable for one combination of user, task and environmental conditions but totally unsuitable for another. One design aspect which can greatly contribute to the design’s usability, whether it is a case of a single product or a complex system, is the consideration of cultural aspects which have a profound influence on both the user and the operating environment.
Even if a conscientious engineer designs a proper human-machine interface for use in a given environment, the designer is often unable to foresee the effects of a different culture on the product’s usability. It is difficult to prevent possible negative cultural effects when a product is used in an environment different from that for which it was designed. And since there exist almost no quantitative data regarding cultural constraints, the only way the engineer can make the design compatible with regard to cultural factors is to actively integrate the user population in the design process.
The best way to consider cultural aspects in design is for the designer to adapt a user-centred design approach. True enough, the design approach adapted by the designer is the essential factor that will instantly influence the usability of the designed system. The importance of this basic concept must be recognized and implemented by the product or system designer at the very beginning of the design life cycle. The basic principles of user-centred design can thus be summarized as follows (Gould and Lewis 1985; Shackel 1986; Gould et al. 1987; Gould 1988; Wang 1992):
In the case of designing a product on a global scale, the designer has to consider the needs of consumers around the world. In such a case, access to all actual users and operating environments may not be possible for the purpose of adopting a user-centred design approach. The designer has to use a broad range of information, both formal and informal, such as literature reference material, standards, guidelines, and practical principles and experience in making an analytical evaluation of the design and has to provide sufficient adjustability and flexibility in the product in order to satisfy the needs of a wider user population.
Another point to consider is the fact that designers can never be all-knowing. They need input from not only the users but also other parties involved in the project, including managers, technicians, and repair and maintenance workers. In a participatory process, people involved should share their knowledge and experiences in developing a usable product or system and accept collective responsibility for its functionality and safety. After all, everyone involved has something at stake.
The status of ageing workers varies according to their functional condition, which itself is influenced by their past working history. Their status also depends on the work post that they occupy, and the social, cultural and economic situation of the country in which they live.
Thus, workers who have to perform much physical labour are also, most often, those who have had the least schooling and the least occupational training. They are subject to exhausting work conditions, which can cause disease, and they are exposed to the risk of accidents. In this context, their physical capacity is very likely to decline towards the end of their active life, a fact that makes them more vulnerable at work.
Conversely, workers who have had the advantage of lengthy schooling, followed by occupational training that equips them for their work, in general practise trades where they can put to use the knowledge thus acquired and progressively widen their experience. Often they do not work in the most harmful occupational environments and their skills are recognized and valued as they grow older.
During a period of economic expansion and shortage of labour, ageing workers are recognized as having the qualities of “occupational conscientiousness”, being regular in their work, and being able to keep up their know-how. In a period of recession and unemployment, there will be greater emphasis on the fact that their work performance falls short of that of younger people and on their lower capacity to adapt to changes in work techniques and organization.
Depending on the countries concerned, their cultural traditions and their mode and level of economic development, consideration for ageing workers and solidarity with them will be more or less evident, and their protection will be more or less assured.
The time dimensions of the age/work relationship
The relationship between ageing and work covers a great diversity of situations, which can be considered from two points of view: on the one hand, work appears to be a transformation factor for the worker throughout his or her active life, the transformations being either negative (e.g., wear and tear, decline in skills, illnesses and accidents) or positive (e.g., acquisition of knowledge and experience); on the other hand, work reveals the changes connected with age, and this results in marginalization and even exclusion from the production system for older workers exposed to demands at work that are too great for their declining capacity, or on the contrary allows for progress in their working career if the content of the work is such that a high value is placed on experience.
Advancing age therefore plays the role of a “vector” on which events in life are registered chronologically, both at and outside work. Around this axis are hinged processes of decline and building, which are very variable from one worker to another. In order to take into account the problems of ageing workers in the design of work situations, it is necessary to take into account both the dynamic characteristics of changes connected with age and the variability of these changes among individuals.
The age/work relationship can be considered in the light of a threefold evolution:
Some processes of organic ageing and their relationship to work
The main organic functions involved in work decline in an observable way from the ages of 40 or 50, after some of them have undergone development up to the ages of 20 or 25.
In particular, a decline with age is observed in maximum muscular strength and range of joint movement. The reduction in strength is in the order of 15 to 20% between the ages of 20 and 60. But this is only an overall trend, and the variability among individuals is considerable. Moreover, these are maximum capacities; the decline is much less for more moderate physical demands.
One function that is very sensitive to age is regulation of posture. This difficulty is not very apparent for common and stable working positions (standing or sitting) but it becomes obvious in situations of disequilibrium that require precise adjustments, strong muscular contraction or joint movements at extreme angles. These problems become more severe when the work has to be carried out on unstable or slippery supports, or when the worker suffers a shock or unexpected jolt. The result is that accidents due to loss of balance become more frequent with age.
Sleep regulation becomes less reliable from the ages of 40 to 45 onwards. It is more sensitive to changes in working schedules (such as night work or shift work) and to disturbing environments (e.g., noise or lighting). Changes in the length and quality of sleep follow.
Thermoregulation also becomes more difficult with age, and this causes older workers to have specific problems with regard to work in heat, particularly when physically intense work has to be carried out.
Sensory functions begin to be affected very early, but the resulting deficiencies are rarely marked before the ages of 40 to 45. Visual function as a whole is affected: there is a reduction in the amplitude of accommodation (which can be corrected with appropriate lenses), and also in the peripheral visual field, perception of depth, resistance to glare and light transmission through the crystalline lens. The resulting inconvenience is noticeable only in particular conditions: in poor lighting, near sources of glare, with objects or texts of very small size or badly presented, and so on.
The decline in auditory function affects the hearing threshold for high frequencies (high-pitched sounds), but it reveals itself particularly as difficulty in discriminating sound signals in a noisy environment. Thus, the intelligibility of the spoken word becomes more difficult in the presence of ambient noise or strong reverberation.
The other sensory functions are, in general, little affected at this time of life.
It can be seen that, in a general way, organic decline with age is noticeable particularly in extreme situations, which should in any case be modified to avoid difficulties even for young workers. Moreover, ageing workers can compensate for their deficiencies by means of particular strategies, often acquired with experience, when the work conditions and organization permit: the use of additional supports for unbalanced postures, lifting and carrying loads in such a way as to reduce extreme effort, organizing visual scanning so as to pinpoint useful information, among other means.
Cognitive ageing: slowing down and learning
As regards cognitive functions, the first thing to note is that work activity brings into play basic mechanisms for receiving and processing information on the one hand, and on the other, knowledge acquired throughout life. This knowledge concerns mainly the meaning of objects, signals, words and situations (“declarative” knowledge), and ways of doing things (“procedural” knowledge).
Short-term memory allows us to retain, for some dozens of seconds or for some minutes, useful information that has been detected. Processing of this information is carried out by comparing it with knowledge that has been memorized on a permanent basis. Ageing acts on these mechanisms in various ways: (1) by virtue of experience, it enriches knowledge, the capacity to select in the best way both useful knowledge and the method of processing it, especially in tasks that are carried out fairly frequently, but (2) the time taken to process this information is lengthened owing both to ageing of the central nervous system, and to more fragile short-term memory.
These cognitive functions depend very much on the environment in which the workers have lived, and therefore on their past history, their training, and the work situations which they have had to face. The changes that occur with age are therefore manifested in extremely varied combinations of phenomena of decline and reconstruction, in which each of these two factors may be more or less accentuated.
If in the course of their working lives workers have received only brief training, and if they have had to carry out relatively simple and repetitive tasks, their knowledge will be limited and they have difficulties when confronted with new or relatively unfamiliar tasks. If, moreover, they have to perform work under marked time constraints, the changes that have occurred in their sensory functions and the slowing down of their information processing will handicap them. If, on the other hand, they have had lengthy schooling and training, and if they have had to carry out a variety of tasks, they will thereby have been able to enhance their skills so that the sensory or cognitive deficiencies associated with age will be largely compensated for.
It is therefore easy to understand the role played by continued training in the work situation of ageing workers. Changes in work make it necessary more and more often to have recourse to periodic training, but older workers rarely receive it. Firms frequently do not consider it worthwhile to give training to a worker nearing the end of his or her active life, particularly as learning difficulties are thought to increase with age. And the workers themselves hesitate to undergo training, fearing that they will not succeed, and not always seeing very clearly the benefits that they could derive from training.
In fact, with age, the manner of learning is modified. Whereas a young person records the knowledge transmitted to him, an older person needs to understand how this knowledge is organized in relation to what he or she already knows, what is its logic, and what is its justification for work. He or she also needs time to learn. Therefore one response to the problem of training older workers is, in the first place, to use different teaching methods, according to each person’s age, knowledge and experience, with, in particular, a longer training period for older people.
Ageing of men and women at work
Age differences between men and women are found at two different levels. At the organic level, life expectancy is generally greater for women than for men, but what is called life expectancy without disability is very close for the two sexes—up to 65 to 70 years. Beyond that age, women are generally at a disadvantage. Moreover, women’s maximum physical capacity is on average 30% less than men’s, and this difference tends to persist with advancing age, but the variability in the two groups is wide, with some overlap between the two distributions.
At the level of the working career there are great differences. On average, women have received less training for work than men when they start their working life, they most often occupy posts for which fewer qualifications are needed, and their working careers are less rewarding. With age they, therefore, occupy posts with considerable constraints, such as time constraints and repetitiveness of the work. No sexual difference in the development of cognitive capacity with age can be established without reference to this social context of work.
If the design of work situations is to take account of these gender differences, action must be taken especially in favour of the initial and continuing vocational training of women and constructing work careers that increase women’s experiences and enhance their value. This action must, therefore, be taken well before the end of their active lives.
Ageing of working populations: the usefulness of collective data
There are at least two reasons for adopting collective and quantitative approaches with respect to the ageing of the working population. The first reason is that such data will be necessary in order to evaluate and foresee the effects of ageing in a workshop, a service, a firm, a sector or a country. The second reason is that the main components of ageing are themselves phenomena subject to probability: all workers do not age in the same way or at the same rate. It is therefore by means of statistical tools that various aspects of ageing will sometimes be revealed, confirmed or assessed.
The simplest instrument in this field is the description of age structures and of their evolution, expressed in ways relevant to work: economic sector, trade, group of jobs, and so on.
For example, when we observe that the age structure of a population in a workplace remains stable and young, we may ask which characteristics of the work could play a selective role in terms of age. If, on the contrary, this structure is stable and older, the workplace has the function of receiving people from other sectors of the firm; the reasons for these movements are worth studying, and we should equally verify whether the work in this workplace is suited to the characteristics of an ageing workforce. If, finally, the age structure shifts regularly, simply reflecting recruitment levels from one year to another, we probably have a situation where people “grow old on site”; this sometimes requires special study, particularly if the annual number of recruitments is tending to decline, which will shift the overall structure towards higher age groups.
Our understanding of these phenomena can be enhanced if we have quantitative data on working conditions, on the posts currently occupied by the workers and (if possible) on the posts that they no longer occupy. The work schedules, the repetitiveness of work, the nature of the physical demands, the work environment, and even certain cognitive components, can be the subject of queries (to be asked of the workers) or of evaluations (by experts). It is then possible to establish a connection between the characteristics of the present work and of past work, and the age of the workers concerned, and so to elucidate the selection mechanisms to which the work conditions can give rise at certain ages.
These investigations can be further improved by also obtaining information on the health status of the workers. This information can be derived from objective indicators such as the work accident rate or sickness absence rate. But these indicators often require considerable care as regards methodology, because although they do indeed reflect health conditions that may be work-related, they also reflect the strategy of all those concerned with occupational accidents and absence due to illness: the workers themselves, the management and the physicians can have various strategies in this regard, and there is no guarantee that these strategies are independent of the worker’s age. Comparisons of these indicators between ages are therefore often complex.
Recourse will therefore be had, when possible, to data arising from self-evaluation of health by the workers, or obtained during medical examinations. These data may relate to diseases whose variable prevalence with age needs to be better known for purposes of anticipation and prevention. But the study of ageing will rely above all on the appreciation of conditions that have not reached the disease stage, such as certain types of functional deterioration: (e. g., of the joints—pain and limitation of sight and hearing, of the respiratory system) or else certain kinds of difficulty or even incapacity (e. g. in mounting a high step, making a precise movement, maintaining equilibrium in an awkward position).
Relating data concerning age, work and health is therefore at the same time a useful and complex matter. Their use permits various types of connections to be revealed (or their existence to be presumed). It may be a case of simple causal relationships, with some requirement of the work accelerating a type of decline in the functional state as age advances. But this is not the most frequent case. Very often, we shall be led to appreciate simultaneously the effect of an accumulation of constraints on the a set of health characteristics, and at the same time the effect of selection mechanisms in accordance with which workers whose health has declined may find that they are excluded from certain kinds of work (what the epidemiologists call the “healthy worker effect”).
In this way we can evaluate the soundness of this collection of relationships, confirm certain fundamental knowledge in the sphere of psychophysiology, and above all obtain information that is useful for devising preventive strategies as regards ageing at work.
Some types of action
Action to be undertaken to maintain ageing workers in employment, without negative consequences for them, must follow several general lines:
On the basis of these few principles, several types of immediate action can first be defined. The highest priority of action will concern working conditions that are capable of posing particularly acute problems for older workers. As mentioned earlier, postural stresses, extreme exertion, strict time constraints (e.g., as with assembly-line work or the imposition of higher output goals), harmful environments (temperature, noise) or unsuitable environments (lighting conditions), night work and shift work are examples.
Systematic pinpointing of these constraints in posts that are (or may be) occupied by older workers allows an inventory to be drawn up and priorities to be established for action. This pinpointing can be carried out by means of empirical inspection checklists. Of equal use will be analysis of worker activity, which will permit observation of their behaviour to be linked with the explanations that they give of their difficulties. In these two cases, measures of effort or of environmental parameters may complete the observations.
Beyond this pinpointing, the action to be taken cannot be described here, since it will obviously be specific to each work situation. The use of standards may sometimes be useful, but few standards take account of specific aspects of ageing, and each one is concerned with a particular domain, which tends to give rise to thinking in an isolated fashion about each component of the activity under study.
Apart from the immediate measures, taking ageing into account implies longer-range thinking directed towards working out the widest possible flexibility in the design of work situations.
Such flexibility must first be sought in the design of work situations and equipment. Restricted space, nonadjustable tools, rigid software, in short, all the characteristics of the situation that limit the expression of human diversity in the carrying out of the task are very likely to penalize a considerable proportion of older workers. The same is true of the more constraining types of organization: a completely predetermined distribution of tasks, frequent and urgent deadlines, or too numerous or too strict orders (these, of course, must be tolerated when there are essential requirements relating to the quality of production or the safety of an installation). The search for such flexibility is, therefore, the search for varied individual and collective adjustments that can facilitate the successful integration of ageing workers into the production system. One of the conditions for the success of these adjustments is obviously the establishment of work training programmes, provided for workers of all ages and geared to their specific needs.
Taking ageing into account in the design of work situations thus entails a series of coordinated actions (overall reduction in extreme stresses, using all possible strategies for work organization, and continuous efforts to increase skills), which are all the more efficient and all the less expensive when they are taken over the long term and are carefully thought out in advance. The ageing of the population is a sufficiently slow and foreseeable phenomenon for appropriate preventive action to be perfectly feasible.
Designing for Disabled Persons is Designing for Everyone
There are so many products on the market that readily reveal their unfitness for the general population of users. What evaluation should one make of a doorway too narrow to comfortably accommodate a stout person or pregnant woman? Shall its physical design be faulted if it satisfies all relevant tests of mechanical function? Certainly such users cannot be regarded as disabled in any physical sense, since they may be in a state of perfect health. Some products need considerable handling before one can force them to perform as desired—certain inexpensive can openers come, not altogether trivially, to mind. Yet a healthy person who may experience difficulty operating such devices need not be considered disabled. A designer who successfully incorporates considerations of human interaction with the product enhances the functional utility of his or her design. In the absence of good functional design, people with a minor disability may find themselves in the position of being severely hampered. It is thus the user-machine interface that determines the value of design for all users.
It is a truism to remind oneself that technology exists to serve human beings; its use is to enlarge their own capabilities. For disabled persons, this enlargement has to be taken some steps further. For instance in the 1980s, a good deal of attention was paid to the design of kitchens for disabled people. The experience gained in this work penetrated design features for “normal” kitchens; the disabled person in this sense may be considered a pioneer. Occupationally-induced impairments and disabilities—one has but to consider the musculoskeletal and other complaints suffered by those confined to sedentary tasks so common in the new workplace—similarly call for design efforts aimed not only also preventing the recurrence of such conditions, but at the development of user-compatible technology adapted to the needs of workers already affected by work-related disorders.
The Broader Average Person
The designer should not focus on a small, unrepresentative population. Among certain groups it is most unwise to entertain assumptions concerning similarities among them. For example, a worker injured in a certain way as an adult may not necessarily be anthropometrically quite so different from an otherwise comparable, healthy person, and may be considered as part of the broad average. A young child so injured will display a considerably different anthropometry as an adult since his muscular and mechanical development will be steadily and sequentially influenced by preceding growth stages. (No conclusions as to comparability as adults ought to be ventured as regards the two cases. They must be regarded as two distinct, specific groups, only the one being included among the broad average.) But as one strives for a design suitable for, say, 90% of the population, one should exert fractionally greater pains to increase this margin to, say, 95%, the point being that in this way the need for design for specific groups can be reduced.
Another way to approach design for the broader average population is to produce two products, each one designed roughly to fit the two percentile extremes of human differences. Two sizes of chair, for instance, might be built, the one with brackets allowing it to be adjusted in height from 38 to 46 cm, and the other one from 46 to 54 cm; two sizes of pliers already exist, one fitting larger and average sizes of men’s hands and the other fitting average women’s hands and hands of smaller men.
It would be a well-advised company policy to reserve annually a modest amount of money to have worksites analysed and made more suitable for workers, a move that would prevent illness and disability due to excessive physical load. It also increases the motivation of workers when they understand that management is actively trying to improve their work environment, and more impressively so when elaborate measures sometimes have to be undertaken: thorough work analysis, the construction of mock-ups, anthropometrical measurements, and even the specific design of units for the workers. In a certain company, in fact, the conclusion was that the units should be redesigned at every worksite because they caused physical overload in the form of too much standing, there were unsuitable dimensions associated with the seated positions, and there were other deficiencies as well.
Costs, Benefits and Usability of Design
Cost/benefit analyses are developed by ergonomists in order to gain insight into the results of ergonomic policies other than those that are economic. In the present day, evaluation in the industrial and commercial realms includes the negative or positive impact of a policy on the worker.
Methods of evaluating quality and usability are currently the subject of active research. The Rehabilitation Technology Useability Model (RTUM), as shown in figure 1, can be utilized as a model for evaluating the usability of a product within rehabilitation technology and to illuminate the various aspects of the product which determine its usability.
Figure 1. The Rehabilitation Technology Useability Model (RTUM)
From the strictly economic point of view, the costs of creating a system in which a given task can be performed or in which a certain product can be made can be specified; it scarcely needs mentioning that in these terms each company is interested in a maximum return on its investment. But how can the real costs of task performance and product manufacturing in relation to financial investment be determined when one takes into account the varying exertions of workers’ physical, cognitive and mental systems? In fact, the judging of human performance itself is, among other factors, based on the workers’ perception of what has to be done, their view of their own value in doing it, and their opinion of the company. It is actually the intrinsic satisfaction with work that is the norm of value in this context, and this satisfaction, together with the aims of the company, constitute one’s reason for performing. Worker well-being and performance are thus based on a wide spectrum of experiences, associations and perceptions that determine attitudes towards work and the ultimate quality of performance—an understanding upon which the RTUM model is predicated.
If one does not accept this view, it becomes necessary to regard investment only in relation to doubtful and unspecified results. If ergonomists and physicians wish to improve the work environment of disabled people—to produce more from machine operations and enhance the usability of the tools used—they will encounter difficulties in finding ways to justify the financial investment. Typically, such justification has been sought in savings realized by prevention of injury and illness due to work. But if the costs of illness have been borne not by the company but by the state, they become financially invisible, so to speak, and are not seen as work-related.
Nevertheless, the awareness that investment in a healthy working environment is money well spent has been growing with the recognition that the “social” costs of incapacities are translatable in terms of ultimate costs to a country’s economy, and that value is lost when a potential worker is sitting about at home making no contribution to society. Investing in a workplace (in terms of adapting a work station or providing special tools or perhaps even help in personal hygiene) can not only reward a person with job satisfaction but can help make him or her self-sufficient and independent of social assistance.
Cost/benefit analyses can be carried out in order to determine whether special intervention in the workplace is justified for disabled persons. The following factors represent sources of data that would form the object of such analyses:
As concerns time lost from work, these calculations can be made in terms of wages, overhead, compensation and lost production. The sort of analyses just described represents a rational approach by which an organization can arrive at an informed decision as to whether a disabled worker is better off back on the job and whether the organization itself will gain by his or her return to work.
In the preceding discussion, designing for the broader population has received a focus of attention heightened by emphasis on specific design in relation to usability and the costs and benefits of such design. It is still a difficult task to make the needed calculations, including all relevant factors, but at present, research efforts are continuing that incorporate modelling methods in their techniques. In some countries, for example the Netherlands and Germany, government policy is making companies more responsible for job-related personal harm; fundamental changes in regulatory policies and insurance structures are, clearly, to be expected to result from trends of this sort. It has already become a more or less settled policy in these countries that a worker who suffers a disabling accident at work should be provided with an adapted work station or be able to perform other work within the company, a policy that has made the treatment of the disabled a genuine achievement in the humane treatment of the worker.
Workers with Limited Functional Capacity
Whether design is aimed at the disabled or at the broader average, it is hindered by a scarcity of research data. Handicapped people have been the subjects of virtually no research efforts. Therefore, in order to set up a product requirements document, or PRD, a specific empirical research study will have to be undertaken in order to gather that data by observation and measurement.
In gathering the information needed about the disabled worker or user it is necessary to consider not only the current functional status of the disabled person, but to make the attempt to foresee whatever changes might be the result of the progression of a chronic condition. This kind of information can, in fact, be elicited from the worker directly, or a medical specialist can supply it.
In designing, for instance, a work action to which data about the worker’s physical strength is relevant, the designer will not choose as a specification the maximum strength which the disabled person can exert, but will take into account any possible diminution in strength that a progression in the worker’s condition might bring about. Thus the worker will be enabled to continue to use the machines and tools adapted or designed for him or at the work station.
Furthermore, designers should avoid designs that involve manipulations of the human body at the far extremes of, say, the range of motion of a body part, but should accommodate their designs to the middle ranges. A simple but very common illustration of this principle follows. A very common part of the drawers of kitchen and office cabinets and desks is a handle that has the form of a little shelf under which one places the fingers, exerting upward and forward force to open the drawer. This manoeuvre requires 180 degrees of supination (with the palm of the hand up) in the wrist—the maximum point for the range of this sort of motion of the wrist. This state of affairs may present no difficulty for a healthy person, provided that the drawer can be opened with a light force and is not awkwardly situated, but makes for strain when the action of the drawer is tight or when the full 180-degree supination is not possible, and is a needless burden on a disabled person. A simple solution—a vertically placed handle—would be mechanically far more efficient and more easily manipulated by a larger portion of the population.
Physical Functioning Ability
In what follows, the three chief areas of limitation in physical functional ability, as defined by the locomotion system, the neurological system and the energy system, will be discussed. Designers will gain some insight into the nature of user/worker constraints in considering the following basic principles of bodily functions.
The locomotion system. This consists of the bones, joints, connective tissues and muscles. The nature of the joint structure determines the range of motion possible. A knee joint, for example, shows a different degree of movement and stability than the joint of the hip or the shoulder. These varying joint characteristics determine the actions possible to the arms, hands, feet, and so on. There are also different types of muscle; it is the type of muscle, whether the muscle passes over one or two joints, and the location of the muscle that determines, for a given body part, the direction of its movement, its speed, and the strength which it is capable of exerting.
The fact that this direction, speed and strength can be characterized and calculated is of great importance in design. For disabled people, one has to take it into account that the “normal” locations of muscles have been disturbed and that the range of motion in joints has been changed. In an amputation, for instance, a muscle may function only partly, or its location may have changed, so that one has to examine the physical ability of the patient carefully to establish what functions remain and how reliable they may be. A case history follows.
A 40-year-old carpenter lost his thumb and the third finger of his right hand in an accident. In an effort to restore the carpenter’s capacity for work, a surgeon removed one of the patient’s great toes and he replaced the missing thumb with it. After a period of rehabilitation, the carpenter returned to work but found it impossible to do sustained work for more than three to four hours. His tools were studied and found to be unfitted to the “abnormal” structure of his hand. The rehabilitation specialist, examining the “redesigned” hand from the point of view of its new functional ability and form was able to have new tools designed that were more appropriate and usable with respect to the altered hand. The load on the worker’s hand, previously too heavy, was now within a usable range, and he regained his ability to continue work for a longer time.
The neurological system. The neurological system can be compared to a very sophisticated control room, complete with data collectors, whose purpose it is to initiate and govern one’s movements and actions by interpreting information relating to those aspects of the body’s components relating to position and mechanical, chemical and other states. This system incorporates not only a feedback system (e.g., pain) that provides for corrective measures, but a “feed-forward” capability which expresses itself anticipatorily so as to maintain a state of equilibrium. Consider the case of a worker who reflexively acts so as to restore a posture in order to protect himself from a fall or from contact with dangerous machine parts.
In disabled persons, the physiological processing of information can be impaired. Both the feedback and the feed-forward mechanisms of visually impaired people are weakened or absent, and the same is true, on an acoustic level, among the hearing-impaired. Furthermore the important governing circuits are interactive. Sound signals have an effect on the equilibrium of a person in conjunction with proprioceptive circuits that situate our bodies in space, so to speak, via data gathered from muscles and joints, with the further help of visual signals. The brain can function to overcome quite drastic deficiencies in these systems, correcting for errors in the coding of information and “filling in” missing information. Beyond certain limits, to be sure, incapacity supervenes. Two case histories follow.
Case 1. A 36-year-old woman suffered a lesion of the spinal cord due to an automobile accident. She is able to sit up without assistance and can move a wheelchair manually. Her trunk is stable. The feeling in her legs is gone, however; this defect includes an inability to sense temperature changes.
She has a sitting workplace at home (the kitchen is designed to allow her to work in a seated position). The safety measure has been taken of installing a sink in a position sufficiently isolated that the risk of burning her legs with hot water is minimized, since her inability to process temperature information in the legs leaves her vulnerable to being unaware of being burned.
Case 2. A five-year-old boy whose left side was paralysed was being bathed by his mother. The doorbell rang, the mother left the boy alone to go to the front door, and the boy, turning on the hot-water tap, suffered burns. For safety reasons, the bath should have been equipped with a thermostat (preferably one that the boy could not have overridden).
The energy system. When the human body has to perform physical labour, physiological changes, notably in the form of interactions in the muscle cells, take place, albeit relatively inefficiently. The human “motor” converts only about 25% of its energy supply to mechanical activity, the remainder of the energy representing thermal losses. The human body is therefore not especially suited to heavy physical labour. Exhaustion sets in after a certain time, and if heavy labour has to be performed, reserve energy sources are drawn upon. These sources of reserve energy are always used whenever work is carried out very rapidly, is started suddenly (without a warm-up period) or involves heavy exertion.
The human organism obtains energy aerobically (via oxygen in the bloodstream) and anaerobically (after depleting aerobic oxygen, it calls upon small, but important reserve units of energy stored in muscle tissue). The need for fresh air supplies in the workplace naturally draws the focus of discussion of oxygen usage toward the aerobic side, working conditions that are strenuous enough to call forth anaerobic processes on a regular basis being extraordinarily uncommon in most workplaces, at least in the developed countries. The availability of atmospheric oxygen, which relates so directly to human aerobic functioning, is a function of several conditions:
A person suffering from asthma or bronchitis, both of which are diseases affecting the lungs, causes the worker severe limitation in his or her work. The work assignment of this worker should be analysed with respect to factors such as physical load. The environment should be analysed as well: clean ambient air will contribute substantially to workers’ well-being. Furthermore, the workload should be balanced through the day, avoiding peak loads.
In some cases, however, there is still a need for specific design, or design for very small groups. Such a need arises when the tasks to be performed and the difficulties a disabled person is experiencing are excessively large. If the needed specific requirements cannot be made with the available products on the market (even with adaptations), specific design is the answer. Whether this sort of solution may be costly or cheap (and aside from humanitarian issues) it must be nonetheless regarded in the light of workability and support to the firm’s viability. A specially designed worksite is worthwhile economically only when the disabled worker can look forward to working there for years and when the work he or she does is, in production terms, an asset to the company. When this is not the case, although the worker may indeed insist upon his or her right to the job, a sense of realism should prevail. Such touchy problems should be approached in a spirit of seeking a solution by cooperative endeavours at communication.
The advantages of specific design are as follows:
The disadvantages of specific design are:
Case 1. For example, there is the case of a receptionist in a wheelchair who had a speech problem. Her speech difficulty made for rather slow conversations. While the firm remained small, no problems arose and she continued to work there for years. But when the firm enlarged, her disabilities began to make themselves problematic. She had to speak more rapidly and to move about considerably faster; she could not cope with the new demands. However, solutions to her troubles were sought and reduced themselves to two alternatives: special technical equipment might be installed so that the deficiencies that degraded the quality of some of her tasks could be compensated for, or she could simply choose a set of tasks involving a more desk-bound workload. She chose the latter course and still works for the same company.
Case 2. A young man, whose profession was the production of technical drawings, suffered a high level spinal cord lesion due to diving in shallow waters. His injury is severe enough for him to require help with all his daily activities. Nevertheless, with the help of a computer-aided design (CAD) software, he continues to be able make his living at technical drawing and lives, financially independent, with his partner. His work space is a study adapted for his needs and he works for a firm with which he communicates by computer, phone and fax. To operate his personal computer, he had to have certain adaptations made to the keyboard. But with these technical assets he can earn a living and provide for himself.
The approach for specific design is not different from other design as described above. The only insurmountable problem that may arise during a design project is that the design objective cannot be achieved on purely technical grounds—in other words, it can’t be done. For example, a person suffering from Parkinson’s disease is prone, at a certain stage in the progression of his or her condition, to fall over backwards. An aid which would prevent such an eventuality would of course represent the desired solution, but the state of the art is not such that such a device can yet be built.
System Ergonomic Design and Workers with Special Physical Needs
One can treat bodily impairment by medically intervening to restore the damaged function, but the treatment of a disability, or deficiency in the ability to perform tasks, can involve measures far less developed in comparison with medical expertise. As far as the necessity of treating a disability is concerned, the severity of the handicap strongly influences such a decision. But given that treatment is called for, however, the following means, taken singly or in combination, form the choices available to the designer or manager:
From the specific ergonomic point of view, treatment of a disability includes the following:
The issue of efficacy is always the point of departure in the modification of tools or machines, and is often related to the costs devoted to the modification in question, the technical features to be addressed, and the functional changes to be embodied in the new design. Comfort and attractiveness are qualities that by no means deserve to be neglected among these other characteristics.
The next consideration relating to design changes to be made to a tool or machine is whether the device is one already designed for general use (in which case, modifications will be made to a pre-existing product) or is to be designed with an individual type of disability in mind. In the latter case, specific ergonomic considerations must be devoted to each aspect of the worker’s disability. For example, given a worker suffering from limitations in brain function after a stroke, impairments such as aphasia (difficulty in communication), a paralysed right arm, and a spastic paresis of the leg preventing its being moved upwards might require the following adjustments:
Is there any general answer to the question of how to design for the disabled worker? The system ergonomic design (SED) approach is an eminently suitable one for this task. Research related to the work situation or to the kind of product at issue requires a design team for the purpose of gathering special information relating either to a special group of disabled workers or to the unique case of an individual user disabled in a particular way. The design team will, by virtue of including a diversity of qualified people, be in possession of expertise beyond the technical sort expected of a designer alone; the medical and ergonomic knowledge shared among them will be as fully applicable as the strictly technical.
Design constraints determined by assembling data related to disabled users are treated with the same objectivity and in the same analytical spirit as are counterpart data relating to healthy users. Just as for the latter, one has to determine for disabled persons their personal patterns of behavioural response, their anthropometrical profiles, biomechanical data (as to reach, strength, range of motion, handling space used, physical load and so forth), ergonomic standards and safety regulations. But one is most regretfully obliged to concede that very little research indeed is done on behalf of disabled workers. There exist a few studies on anthropometry, somewhat more on biomechanics in the field of prostheses and orthoses, but hardly any studies have been carried on physical load capabilities. (The reader will find references to such material in the “Other relevant reading” list at the end of this chapter.) And while it is sometimes easy to gather and apply such data, frequently enough the task is difficult, and in fact, impossible. To be sure, one must obtain objective data, however strenuous the effort and unlikely the chances of doing so, given that the numbers of disabled persons available for research is small. But they are quite often more than willing to participate in whatever research they are offered the opportunity of sharing in, since there is great consciousness of the importance of such a contribution towards design and research in this field. It thus represents an investment not only for themselves but for the larger community of disabled people.