The effectiveness of equipment for the users

AppliedEr,~.onomics ~1.97]. 2.2.1Oa 111

The effectiveness of equipment for the users J. R. de Jong B. W. Berenschot, Amsterdam, The Netherlands To be effective in operation, equipment must be designed both to satisfy functional and economic criteria and to fit the man. This is done best within the concept of designing a complete man-machine system. Some of the methods to be used, and some of the important human factors aspects to be considered, are discussed and illustrated with examples from K L M at Amsterdam Airport.

One of the important realisations, which has developed with the growth of ergonomics alongside engineering, is the value of remembering the larger framework within which equipment is designed, that is the concept of the man-machine system. What occurs in a man-machine system can be shown diagrammatically (see Fig 1) - albeit very simplified when compared with the highly complex situations often found in reality. Frequently the effectiveness of the man-machine system depends to a great extent on the 'man' rather than the 'machine' part of the system. That is, the adaption of the equipment to the capacities, dimensions, requirements and attitudes of those by whom it is employed, operated, transported, maintained or repaired, is an essential requirement. From the human factors viewpoint, two basic criteria are usually applied nowadays in judging the suitability of a man-machine system (and consequently, of such components as the equipment used), viz:

In this connection we distinguish three areas, namely the physical stresses area, the information stresses area and the satisfactoriness area. In the first two areas the emphasis lies on the extent of the strains as compared to the relevant capabilities. The third area is concerned with the degree in

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1. The individual well-being of the people in the system; 2. The system effectiveness. The latter is determined by the value of the system outputs on the one hand, compared with, on the other hand, the sacrifices resulting from the system's existence and functioning. As far as system effectiveness is concerned, this appears to be decided by a balance of opposites as shown in Table 1. Now the invariable aim is to arrive at system effectiveness through optimization, ie by minimizing the cost/output value ratio. This optimization always has technological, economic and human factors aspects. In principle, the contribution of human factors to optimization may relate to all output variables and all system elements (including those of the equipment), because they may all influence the people within the system and the effects of human action. The extent to which ergonomic aspects must, in practice, be involved in the optimization varies and must be determined separately for each specific occasion. As regards individual well-being, one is interested in the stresses to which man in the system is exposed, and the strains caused by them. The stresses are linked to man's inputs (relevant information, noise, heat etc) and to his outputs (motions, forces, providing oral information, etc).

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AppliedErgonomics June 1971

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Fig 1

The functioning of man-machine systems.

Table 1 The balance of opposites determining system effectiveness.

System costs with such elements as:

Value of system outputs (main product, by-products, waste products)

Input costs (raw materials, energy etc)

Quality (including reliability, weight etc)

Personnel costs (including such facets as sk ill, motivation, wages, absences and turnover) Equipment and other

Quantity

costs

Availability (delivery times)

which the demands and possibilities of the situation - as determined by the equipment among other factors correspond to the needs, interests and wishes of those involved. Now, one might be inclined to think that the two basic criteria, ie system effectiveness and individual well-being, are incompatible. However, we believe that by and large this is not the case, because individual well-being normally is a condition for the satisfactory functioning of a system (see Table 2). Experience gained in industry shows that, via attitudes and motivation, well-being is closely related to performance, absenteeism and turnover - all of which are factors co-determining costs and output value - and through them to system effectiveness.

Design for equipment effectiveness

From the foregoing it follows that equipment can never be judged in isolation, and that for a sound evaluation a systems approach is required. This rule holds good in connection with both basic criteria adopted. In the past, the design of equipment from the human factors viewpoint has often been confined to two types of equipment elements, ie the displays intended to provide information (such as instruments), and the controls (handles, pedals, switches, etc) that enable the operator to exercise influence on the functioning of his system. This procedure, however, does not extend beyond the manmachine interface and implies the risk of yielding no more than sub-optimization. It appears desirable, therefore, to consider all networks of the system elements referred to earlier on. Now to ascertain the optimum solution we shall generally have to compare alternatives. In looking at such alternative solutions we need to assess first and foremost how the tasks, that must be accomplished for the system to

Relationships between individual well-being and

Table 2

system effectiveness.

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achieve its mission, are optimally allocated among men and machines in the system. This leads to the question, how far are certain tasks best fulfilled by a human being or by a machine. Fitts (1951) was the first to make an attempt at finding an answer. In a more recent review, Chapanis (1960) mentions, among man's advantages, his ability to handle low probability alternatives (ie unexpected events) and to organize many small pieces of information into meaningful and related 'wholes' (for either activity machines are difficult to programme). At the other end of the scale can be found a range of points in favour of machines, eg for machines the amount handled per unit time can be made almost as large as desired, and that machines are available that are excellent and very rapid computers. In both these areas the human capabilities are far less impressive. For a complete answer we would have to make a breakdown of all activities man can perform, and investigate whether for'such activities mechanical or electronic alternatives are available. Crossman (1965) has carried this out with regard to the human capacities for information processing. He distinguished 432 types of information processing and then proceeded to assess how far equipment showed the same capabilities. He found that although in recent years technology had gained a lot of ground, there remained certain forms of information processing which only man could accomplish (de Jong, 1968). Now, of course, the possibility of a given task being fulfilled by a machine (in the broadest sense of the term) does not imply that such a task should necessarily be entrusted to machines. A decision on this point requires a cost/effectiveness analysis using data on the following facets: • The immediate effect of the alternatives on the outputs of the system. • The reliability of the alternatives. (How far does it extend? How serious will be the consequences of breakdowns? What possibilities are available for repairs and replacements? What is the lifetime of each alternative?) • The characteristics of the individual jobs for each alternative. (What stresses and strains are involved? What attitudes and motivation to work should be expected, and how will they affect individual well-being and system effectiveness?) As regards this last aspect it is necessary to take into account the fact that, as well as advances in technology, changes in cultural and social standards play a role in shaping the reactions of those concerned to their work situation. For example, over the years the prevailing ideas about heavy muscle work and dirty work have undergone a marked change. As a corollary, there has been a notable relative increase in the costs of muscle work, although and this is equally true of the shifts in social and cultural norms - the extent may vary from one country to another.

Phases in ergonomics applied to equipment design Making a choice from alternatives For ergonomics in the design of man-machine systems to be really effective, it must start in an early stage of the design and development process. When no attention is paid to human factors considerations until a late stage, the results

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are usually less than satisfactory, because by that time decisions have been reached on numerous fundamental issues. Going back on such decisions is liable to cause loss of time and excessive costs. The application of ergonomics, therefore, should commence when the tasks to be accomplished in a given system are to be allocated. As a rule, several phases are discernible in the procedure. This is illustrated with an example bearing on the development and design of an electronic information system, a baggage handling system and related equipment for the K L M (Royal Dutch Airlines), to be installed at the new area of Amsterdam Airport. The mission of the information system envisaged was to gather and supply the information required for the manifold decisions and operations, preceding the departure of each plane, in relation to the passengers (from the moment of their arrival in the Departure Hall), their luggage, the freight to be carried, catering, fuel, etc. Thus the object was to evolve a system in which many hundreds of employees would,be working every day. As a matter of fact, the number of employees and their capacities were variables depending, among other things, on the degree of mechanization eventually chosen. In an early design stage, decisions had to be taken concerning the place (whether centralized or not) where departing passengers should be checked in, the possible use of an electronic information system with a computer memory, the mode of transport of baggage to the aeroplanes, etc. In many ways these decisions already determined the layout of the buildings, the investments required and the future human tasks. In the following stage further decisions were needed. For instance, with regard to passenger check-in, they related to baggage weighing and transmitting the necessary data to the information centre, known as the Operations Room. Table 3 shows the given inputs, the activities called for and the requisite outputs (plus their ultimate destinations). The principal alternatives considered are given in Table 4. In this particular case one of the decisions made was that only one, female, employee would be assigned to each workplace. Thanks to the mechanization of baggage Table 3

transport (a technical problem whose solution presented several difficulties), the employee would not be called upon to do heavy physical work; hence she could best perform her job in a sitting posture. In view of the costs involved, data on baggage weight would not be transmitted automatically, but would be passed on by the employee to the Operations Room with the aid of an electronic

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The checking-in of passengers: inputs and outputs.

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device (and via the computer memory). Thus functional, technological, human factors and economic aspects played a role in arriving at a choice between the available alternatives. Along with anthropometric considerations (related to the expected body measurements of the employees), the decisions taken at this stage determined to a far-reaching extent the layout of the workplaces involved; these would be located in rows on either side of the main baggage belt conveyors (Fig 2). Table 4

Methodology for choice between alternatives Given the desirability of selecting from alternatives, it is important to seek such alternatives as will afford the best possible chance of finding the optimum solution. These alternatives are subjected to a considered choice, in which system effectiveness and individual well-being are adopted as basic yardsticks. It is believed that the application of Ideal Systems Concept (Nadler, 1963, 1967) is useful. Nadler has evolved, and tested in practice, a method which, while practically

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machines that will be required, and the tasks that, broadly speaking, are to be accomplished by human beings. What now remains is the determining of details. Here again we are faced with problems of choice, bearing upon the arrangement of visual indicators and other instruments (and, generally, of information sources), as well as the location of controls (push buttons, switches etc).

discounting any existing solution and taking its cue from the function to be fulfilled, leads to one or a few 'ideal' answers. Such answers need not necessarily be technologically feasible; they are characterized, among other points, by a minimal number of different low-cost inputs and outputs, and by extreme automation. The 'ideal system' thus found then constitutes the starting point in developing a 'technologically workable ideal system'. It is only subsequently that data are gathered for the purpose of working out alternatives that merit consideration. In these alternatives, functions initially allocated to the equipment are partly performed by human beings. The phase thus reached calls for consultation of the largest possible number of persons whose views and ideas may prove useful.

Fig 3 refers to the electronic apparatus which occupies part of the workstation depicted in Fig 2. It shows a first design for the layout of the man-machine interface, and takes little or no account of the sequence of observations or of the activities occurring in relation to each passenger (albeit with variations that are left out of consideration in the present context). This appears from the paths which so the figure demonstrates - must be travelled by both hands and by the eyes when checking in a passenger.

The method outlined has the overriding advantage of permitting near-elimination of the risk that existing solutions should exercise too much influence on the decision-making process.

Fig 4 represents the ultimate layout opted for after consideration of human factors aspects, technological issues and economic factors. The distances per work cycle (ie per passenger) are appreciably shorter than in Fig 3. The expectation is warranted that the layout of Fig 4 allows shorter operating times, and involves less risk of error, than does the layout of the previous figure. The diagrams and

Workstation design In the last discussed design stage the system's major components are determined, ie the equipment and

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Applied Ergonomics

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the distances shown (relative to the left hand and right hand, and to visual observation) do not provide more than a rough comparison of the appropriateness of alternatives. By calling in an industrial engineer (or work study practitioner) who for the comparison of alternatives makes use of a predetermined elemental time system (such as MTM or Work Factor), more reliable data will be obtained. In a comprehensive ergonomic study, depending upon the time and costs available and the importance of the workstation, a full simulation experiment might be set up, to give precise comparison data and also guidance to define selection and training methods to be adopted later. Figs 5 and 6 refer to another workstation or operator post in the same information system. Just as Fig 2, they illustrate how in the choice of dimensions allowance can be made for the body measurements of the operators that are expected to work in the system (both their average and their range of sizes). This applies equally to the dimensions of the furniture, the accessibility of equipment controls, and the visibility of displays.

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In such evaluation studies the number of variables is generally limited compared with the possibilities of simulation during the design process. This is particularly true of the equipment. None the less, system evaluation often points a way towards achieving significant improvements of working methods and work organization. Moreover, as a rule the insights gained can be used to advantage in developing similar new equipment.

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The evaluation of equipment The decisions that need to be taken in the course of developing a new man-machine system rest almost invariably upon available knowledge, and this is the same as far as human factors aspects are concerned. Where a lack of relevant knowledge involves considerable hazards, it will be necessary to acquire supplementary data through symbolic or physical simulation. Depending on the problems that present themselves, non-functional and functional mockups and prototype equipment may be useful in providing such data. On top of this, mockups, etc, may constitute a major source of early information to those who will play a role in the system once it has become operational. Thus they may help towards limiting resistance to change. As essential as testing equipment (and comparing alternatives), by means of approximating the future reality by simulation, is the methodical evaluation of the complete system after it has been in operation for some time. In principle the data to be gathered for the purpose should always cover the following aspects: 1. accomplishment of the mission assigned to the system; 2. personnel performances and well being; 3. equipment operability, reliability, maintainability, etc; 4. the physical surroundings; 5. instructions, training methods, work organization and the like. The following methods are susceptible of being employed in the data-gathering process:

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• observational methods (eg activity sampling); • task performance measurement by means of graphic recorders, etc; • measurement of the individual stresses and strains by physical and physiological methods, in case of high physical (energetic) and high mental loads (measurement of heart rate, sinus arrhythmia, etc); • interviews and questionnaires.

AppliedErgonomics June 1971

Not infrequently validation studies, bearing on the ergonomics aspects of a man-machine system, are made without other factors receiving any attention. Once system effectiveness and individual well-being are accepted side by side as basic criteria, this is illogical. Instead, validation studies should obviously be directed simultaneously at the functional, technological, human factors and economic facets. Also they should include other factors codetermining the attitude and motivation of the people within the system. Important issues are how far the combination of tasks assigned to a worker engages his capabilities, how far he sees the required performance as a challenge, and whether his organizational environment is a source of motivation to him. Jordan has pointed out that, through fear of human error and of automation, man-machine systems have sometimes been developed involving human tasks that elicited such descriptions as: 'the trained ape operator' and 'idiot jobs'. 'Luckily, or unluckily - depending upon one's point of view - this equipment generally did not perform satisfactorily, so the operators in the field had either to use it in an improvised manner or to circumvent it entirely to get the job done' (Jordan, 1962). Mistakes of this kind should be prevented in the development stage. Even so, in planning validation studies one should take into account the possibility of their having been committed. Hence, when preparing interviews and surveys, not merely should questions be formulated on equipment elements, the climate, dimensions of furniture and the like, but also questions should be included about the manner in which the respondent experiences his or her work and work situation (activity rate, independence, variation, scope offered, cooperation, tasks the respondent would like - or not like - to be relieved of, fatigue, etc). With a view to individual welt-being, and also on account of their relationship with system effectiveness, the attitudes, job satisfaction and motivation of the people in the system are too important to be disregarded (c.f. Gagn6, 1962; de Jong and Roggeveen 1969).

Conclusions In judging the effectiveness of equipment, two basic criteria should be applied, viz. the contribution of the equipment to the effectiveness of the system (or systems) of which it forms part, and the individual well-being of

those entrusted with its operation, maintenance, etc. These two criteria do not lead to incompatible results. A primary issue is the optimum allocation of tasks to men and equipment. This involves technological, human factors and economic aspects, which should be decided upon in light of each individual case. In the design and development of man-machine systems (and, consequently, of the requisite equipment) it is desirable to take the human factors aspect into account right from the outset. Application of the 'ideal system concept' (G. Nadler) will be conducive to achieving favourable solutions. During the design phase, any knowledge that is lacking can be acquired through symbolic or physical simulation. Here functional mockups and prototype equipment may offer a meaningful contribution. In many cases, evaluation studies are desirable when new equipment has been operative for some time. In principle, the data to be gathered with this object will always relate to such points as the accomplishment of the mission envisaged, equipment operability and reliability, and personnel performances and well-being. To obtain the data needed, a choice can be made from different types of methods. When conducting evaluation studies (and also, of course, when developing and designing man-machine systems), it is recommended to pay attention to job content, work organization, etc, ie to such factors as the attitudes, job satisfaction and motivation of the people in the system. With a view to individual well-being and also because of their relationship with system effectiveness, these factors are too important to be left out of consideration.

References Chapanis, A. 1960 Human engineering. In: Flagle, C. D., Huggins, W. H. and Roy, R. H. (editors), 'Operations Research and Systems Engineering'. Baltimore: John Hopkins. Crossman, E. R. F. W. 1965 European experience with the changing nature of jobs due to automation. In: 'The requirements of automated jobs'. North American Joint Conference, Washington 1964, Final Report. Paris: OECD. Fitts, P. M. (editor) 1951 'Human Engineering for an Effective Air-Navigation and Traffic-Control System'. Washington DC: National Research Council. Gagn6, R. M. (editor) 1962 'Psychological Principles in System Design'. New York: Holt, Rinehart and Winston. de Jong, J. R. 1968 Arbeit u. Leistung, 22.10, 173-176. Automatisierungsgrad und Ergonomie bei der Systemgestaltung. de Jong, J. R. and Roggeveen, C. 1969 Der sitzende Angestellte und der stehende kunde. In: Grandjean, E. (editor), 'Sittingposture'. London: Taylor & Francis, 234-241. Jordan, N. 1962 Human Factors, 4, 171-175. Motivational problems in human-computer operations. Nadler, G. 1963 'Work Design'. Homewood, Illinois: Richard D. Irwin. Nadler, G. 1967 Management Science, 13.10, B642-B655. An investigation of design methodology.

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