- Email: [email protected]
ERS Annual Conference
Conference ERS Annual Conference Ergonomics Research Society, King's College, Cambridge, 2 - 5 April 1974 The comfortable and comprehensive facilities at King's College were much appreciated by the delegates to this year's annual conference of the Society who, as usual, were presented with a full programme. Sessions were devoted to a n t h r o p o m e t r y and design; health, travel and human efficiency; the validity o f measurement techniques in ergonomics; behaviour analysis; and the ergonomic approach to systems engineering. In addition, there were a number of individual papers reflecting the ergonomist's breadth of interest, The Society's Lecture was given by Prof R.J. Scothorne on "The Borderland o f A n a t o m y and Ergonomics". During the meeting, the 25th annual dinner o f the Society was held, and the Bartlett Medal was presented to Prof Walter Rohmert. The programme showed 185 registered delegates, representing 7 countries in addition to the United Kingdom. A useful feature introduced this year was a brief listing of the special interests of each delegate, which facilitated the unofficial discussions which are a valuable part of such conferences,
Applying r u m r c h The opening address was given by Mr D.B. Welbourne, Vice-president for the Society for the Application of Research, and Director in Industrial C o o p e r a t i o n for the University. He discussed some aspects of getting academic research applied, pointing out that the University could probably claim the first piece of academic consultancy when in 1610 Edward Wright u n d e r t o o k the necessary mathematics to get the levelling correct when the Lee Valley water was brought into London. He spoke of the functions of the Wolfson Cambridge Industrial Unit, including the handling of enquiries from industry for advice, a situation in which often the people in industry were not aware of what help could be expected, while those in the academic world did not appreciate some of the practical aspects such as relating the expenditure of time with that of money, He regarded as very important the location of areas of research in the University that could be applied if industry and commerce would take note. One of the best ways of i 10
Applied Ergonomics June 1974
propagating the research results was to place a student in a firm or for the firm to second people to the research unit at the University from one to three years. This would enable the background thinking behind the research to be absorbed and enable industry to learn of the mistakes that had been made which, not unnaturally, were seldom published. As examples of the classical developments in this field he quoted gas turbines of the 1940s, steel work of the 1950s, the scanning light electron microscope of the 1960s and for the 1970s he forecast computer graphics applied to numerically controlled machine tools, although he did realise that their application would involve some revolutionary thinking in organisations, from the design office to the workshops.
A n t h r o p o m e t r y and design It was not inappropriate for this to be the opening session, as the first paper presented to the Society was on anthropometry. As an introduction, it was pointed out that a n t h r o p o m e t r y was a tool for the criminologist in the mid 19th century, preceding finger prints. Recently it has again become popular, for somewhat different reasons, The o p e n i ~ paper, by D. Thomson and Mrs Joan Ward, o f the University of Technology, Loughborough, covered static and functional anthropometric dimensions of British women. In particular, they were concerned with housing regulations on storage space in the home, pointing out that it should be related to the user's anthropometry. Although building regulations specify some dimensions for such factors as shelf height, for example, the illustrations show that the heights quoted refer to shelves which a given women can just reach with her finge~ tips. This is unsatisfactory as clearly the same women must be able to place and remove articles on the shelf, Similarly, body dimensions appear to be well documented. For example, there is information on forward reach in terms of the distance between the back and the finger tips. However, f o r this to be of practical value it should be related to the individual's reach over an obstruction, such as a working surface below a cupboard. A study carried out with practical conditions in mind produced data which is now
available from the Institute of Consumer Ergonomics at Loughborough. The use of figures for functional reach was important in equipment design. F o r example, reaching onto a shelf with an object held in b o t h hands showed that those with their height below the 5th percentile of the population were only able to make use of 14% of the available storage volume, while even those from the 96 to 100th percentile were only able to utilize 76-9% of the space. Some of the recommended design information was challenged. The study had shown, for example, that the height for a shelf with access over an obstruction for the lowest five percentile population should be no more than 116.1 cm, or for the highest five percentile, 163-2 cm, whereas the design bulletin recommended 170 cm. The authors pointed out that there was a notable decrease in reach with age, typical figures being the maximum heights for a shelf using an object requiring two hands of 133-2 cm for those under 60 years and ! 24.3 cm for the over 60's. It was suggested that twice the accessibility could be achieved by using pull-out storage units rather than fixed shelves. With the smaller floor space requirement, a significant monetary saving could be achieved. Anthropometri© survey Continuing the theme, Captain Nigel lnce, RAMC, at the A r m y Personnel Research Establishment, presented details of an on-going anthropometric survey of the British Army. The results of the Royal Armoured Corps part of the survey were now available from APRE at the Royal Aircraft Establishment, Farnborough, Hants. As an example of the practical aspects of the survey, he pointed out the measurement of reach, this was normally made wit h the shoulder against a wall, but in a vehicle driving situation the driver was able to lean forward against a harness thus giving an effective increase in reach. Similarly, a man's practical sitting height was normally much less than that usually measured in an upright position. Applying the data Some aspects of the application of anthropometric data to work space and equipment design were given by
C.B. Bolton of the Royal Aircraft Establishment. He spoke of a survey carried out in 1970/71 of 2000 RAF aircrew to provide information for aircraft designers and functional clothing designers. He appealed for a better presentation of anthropometric data, as the conventional percentile tables did not reveal the spread of the results. For example, a plot of stature against sitting height showed a wide
scatter, the average sitting height being achieved with individuals from 5 to 6 ft ( I "5- l "8 m) in stature. For a given leg length there could be 5 m (127 mm) variation in arm length. A convention today for aircraft cockpit work is to design for the 3rd to 99th percentile, but he showed that by considering 8 different dimensions, no less than 21 "26% of the population had to be rejected. The effects of the nature of the job should be considered when taking measurements. Rarely was it necessary to stand to attention in a cockpit but when designing for successful use of ejection seats, the b u t t o c k - k n e e c a p measurement was all important. Care must be taken when using data from obsolete surveys, and he spoke of a test rig now being used to measure recruits into the RAF, through which they would again pass at periods in their career providing an up-dating of their survey. Even short term delays, it seems, could be significant; he spoke of a weight variation of no less than 3"5 kg between morning and afternoon weighings of the same individual,
Physiological monitoring A survey on mobile cranes carried out in 1972 showed that no crane driver had worked for more than seven years at the job and that they expected to change their occupation before their 50th birthday. A further study undertaken to monitor continuously heart rate and blood pressure of a crane driver during normal working was reported by T.G. White of Glamorgan Polytechnic, and R.P. Wicks of the University of Surrey, in their paper on the continuous monitoring of physiological conditions by an electrical impedance system. Arising from a difficulty to find suitable equipment, a portable apparatus was developed following discussions with Dr David Wheipton, Principal Physicist of the Department of Medical Physics at the University Hospital (Wales), Cardiff. The noninvasive system operated on the principle of electrical impedance plethysmography. Data was obtained from eight airmen on a crane drivers course at RAF St Athan and the results reported included one subject's
heart rate reaching 130 beats per minute and another having a cardiac output of 81A litres per minute, which is some four times the normal, Although at this stage of the study it is not certain if heart rate or cardiac output can be correlated to blood pressure, it was expected that the percentage stress to which the heart is subjected should be determined and data on respiration has been observed which can perhaps be related to lung volume. A significant difference has been noticed between the results of physiological and mental stress on respiratory rhythms.
Applied anatomy Although much data has been published on the forces which humans can exert on control devices, there has been very little interest in the basic understanding of the muscle functions involved. An applied anatomical study was described by S. Pheasant of the Biomechanics Laboratory at the Royal Free Hospital School of Medicine, who introduced some views on how a knowledge of the torques a person can sustain around limb joints can effect workspace design, using as an example the driving positions of two cars currently in production, Human handedness in a paper on functional asymmetries of hand and eye, Dr G.H. Fisher of the University of Newcastle upon Tyne mentioned the frequent references to the relationship of various types of functional asymmetry. He described experiments using a stereoscope in which parts of an illusion are presented to separate eyes, to be recombined by the viewer, in a further experiment, the sides or directions of examples of functional asymmetry were observed. The results showed that the side of writing hand is related significantly to most of the activities. The results suggested that writing handedness predisposes many asymmetrical functions, that the side of dominant eye is largely irrelevant,
Sexual differences In a paper describing a theory on sex differences in information processing, and some of its possible consequences, Dr June Redgrove of Middlesex Polytechnic concluded that insufficient was known on evaluating the performance on the shop floor of men and women. She suggested that women might require a totally different approach in their work organisation. The problem was not helped by the emphasis in the related work so far carried out being on white
young military males. Furthermore, over a period of time, a job tended to be structured to eliminate those aspects at which people were less competent; thus a situation could arise where the differences between male and female performances were exaggerated if a women took over a task which over a period had been tailored to suit the capacities of a man.
Effectsof Protective clothing After pointing out some discrepancies in the percentage rest allowances made for the wearing of various types of protective clothing, N. Thomas of Glamorgan Polytechnic in his paper on psychological and physiological effects of industrial protective clothing described a study to examine the necessary allowances for recovering from the effects of wearing five given types of protective clothing, compared with ordinary clothes. Observations were taken over cycles including 20 rain work followed by 5 min rest. The results confirmed that a simple heart rate measurement gave a more accurate indication of fatigue than current work study practice relaxation allowances, but that it was necessary to relate the allowances to overall working time. The tests with the given clothing suggested that where the head has to be covered, a compressed air suit is superior to simpler assemblies with, for example, pressurized or nonpressurized respirators.
Commuter health A study on commuter travel and absenteeism carried out when he was with the London School of Hygiene and Tropical Medicine was described by Dr P.J. Taylor, now with the Occupational Health Service of the Post Office. There is a widely held view that commuting is bad for the individual's health, though it seems that there is little supporting evidence, particularly in the case of the shorter journey. Early work that had been done considered commuting in terms of journey distance and duration in relation to the time lost in travelling. By the late 1960s, there seemed to be no economic justification in expanding the London rail network. An investigation was carried out to see if any other justification existed such as the cost to the National Economy arising from commuting induced absenteeism. In general, absenteeism is estimated to cost some £1,700 million per year. A difficulty arose in obtaining a suitable unified population in central London of whom full absence records were kept. Only two organizations
Applied Ergonomics June 1974
111
with 3000 people each were located, one of which was able to co-operate, No less than 24 factors were taken into consideration, including the three regarded as most important: age, sex and status. Others included pay, race, hours of work, epidemics, geography, management attitudes, sick pay, type of journey, length of service, personality, etc.
impressed with the pilot's difficulty in operating a radio which was mounted to his left and behind him during which it was necessary to tuck the collective pitch lever (controlling the aircraft's rise or fall) under his left knee. Holding the map and the control stick in his right hand simultaneously also seemed hazardous since the aircraft was flying at about 80 knots
The median j o u r n e y time was approximately l hr, and the results showed approximately normal d i s t r ~ u t i o n , the shortest j o u r n e y being ! 2½ rain and the longest 2½ hr. Subjective assessment of comfort showed that 3-4% regarded their journeys as very comfortable, 30.5% as fairly comfortable, 35.6% regarded their travel as neither comfortable or uncomfortable, 24.4% classified it as fairly uncomfortable and 6-4% as very uncomfortable. An age relationship was apparent in that 38% of those under 30 thought it was fairly or very uncomfortable while the older people were more tolerant. Sickness absence was both more frequent and longer with those whose journey included three or more separate stages, and the figure was also higher for those who used a car for part of all of their journey. Younger people also had more time off than older, During the investigation, the nation was beset by the epedemic of 'Hong-Kong' flu which resulted in evidence that those travelling by London Transport trains had less absence than those who did not. The general conclusion was that the
at heights sometime below tree-top level, The patterns established by this technique were fairly con~stent between pilots and demonstrated that the pilot spent up to about a third of his time looking at objects inside the cockpit rather than outside, with the rather aggravating additional factor that the lower the aircraft was flying, the more was it necessary to observe instruments and other items inside the cockpit,
complexity of the journey was a more important factor than any of the others.
Helicopter pilot activity One of the most impressive presentations of the conference was made by Dr E.J. Lovesey of the Royal Aircraft Establishment, Farnborough, who presented some film taken in the course of a study of pilot activity within existing types of helicopter. Although a great deal of work has been carried out on many aspects of aviation, most of it is related to fixed-wing aircraft and very little ergonomics has been directed solely towards helicopters. His study was intended to highlight some of the problem areas now existing which could then be studied in greater detail The method adopted consisted of a cine film analysis leading to an activity chart of a pilot's head and hand movements. The camera was fitted with a very wide angle or 'fish-eye' lens. Although this produced a somewhat distorted image, even the lay observers in the audience were clearly
112
Applied Ergonomics June 1974
Power press tool setting Earlier work has been carried out on the operators' work of the power press. A further study has been made by Prof E.N. Corlett and D.I. Mercel" of the Department of Engineering Production at the University of Birmingham, with particular reference to the job of the tool setter. Such machines are running for an average of 52% of the available time, a further 10% is taken up by breakdowns and another 10% is attributed to setting time. This justifies the interest in this area. In addition, more than 50% of the accidents associated with such machines involve the setter when die changing or trying out a new die. A basic problem is the difficult access to the tool for changing the die set. Apart from a basic cleaning up operation to get access to the tool, the setter has to remove the side guards, which usually present little problem, and then the front guard, Usually it is the press user who specifies the type of guard required, rather than the machine manufacturer, a condition not always resulting in the o p t i m u m choice of guard. Front guards may be side hung, pivoting to one side, in which case frequently some controls are isolated when the guard is moved aside, or up swung when it is pivoted upwards and held open by a hook. With presses of more than about ! 0 tons capacity, to do this it is usually necessary to stand on a box, obtain the assistance of a second setter, or use some form of pulley arrangement, Before removal it is necessary to close the die, but only two manufacturers provide efficient stroke and position indicators. Before extracting the top tool, it is necessary
to remove the ram cap and a typical problem here is the need to undo three bolts which are so close together that only about a quarter turn movement can be obtained before changing the position of the spanner. The lower tool is often placed too low for a good view to be obtained. It was observed that setters, when required to exert a pulling action on a bolt, tended to use both hands on the spanner, increasing the likelihood of slipping on a greasy floor. Moreover, setters are required to provide their own tools and consequently tend to use the cheaper open-ended spanners and not the safer ring type. The press fly wheel guard panel is usually fixed by six Philips head screws, and having been once removed is seldom replaced. Only one manufacturer fits wing nuts as an encouragement to refitting. The authors suggested that an improvement could be effected if presses were fitted with a system permitting the press to be "jogged' when the guards had been removed, as this would save considerably in setters' time. Once the press has been placed at top-dead-centre, the die set has to be pulled out onto an adjustable-height platform o n a trolley. This usually requires the assistance of a second setter, who is thus disturbed in his own work with consequent potential dangers when he returns to his own job. The setter has to compare the new shut height of the die set with the old die shut height which he had to note in the first place and has subsequently remembered. None of the firms at which the study was carried out provided steps for setters working at controls and adjustments high above the ground, and the use of old boxes and oil cans produces some spectacular falls. Only one manufacturer fits a 'daylight' indicator, ie, a guide to the distance between the ram face and the press plate, which should equal the shut height of the t o o l With most manufacturers, the data required when making adjustments following tool changing was provided on a legend plate which was not mounted where it could be seen when the adjustments were actually being made. An analysis of the setters' discomfort complaints showed that the most common stress areas were the neck, shoulders, fore-arm and lower back. Mining systems An investigation into the design of the system at the coal face was
reported by A.A. Knight, J.W. Murphy, B. Ward and M. Attfield of the Institute of Occupational Medicine, Edinburgh. After outlining the development of the existing systems they referred to a detailed ergonomics study which was started in 197 i, concentrating on mining machine operators with the three aims of making the men's task more congenial, especially in thin seams, of insuring
1. Many controls, some interacting with each other in their effect, 2. Long time lags, of the order of minutes rather than seconds, between the action and its effect, 3. Numerous output variables to control
that they can perform efficiently with the equipment, and that the men's performance did not impede the performance of the system. Slides emphasised the very difficult conditions in which the miners operated the machines in thin seams from a kneeling position. Frequently the miner had to lean over the machine to use the controls. Whilst this was not difficult if there was adequate headroom, this was not the case in the thinner seams, especially since rocks travelling along the conveyor under the machine had been k n o w n to lift the machines up against the roof of the s e a m .
Ergonomists were interested in such processes because they relied heavily on the skill of the operator in the control and because of the long time required for the operators to obtain the necessary degree of skill for proficient operation. In such systems in industry, the cost of mistakes could frequently be very high, possibly involving a loss of whole shift. The example he used to illustrate his points taken from the glass industry was glass pressing. In the case of colour TV ware, the yield from presses was only of the order of 45%.
Starting with the premise that the contribution ergonomics had actually made to the solution of human problems at work had fallen somewhat short of its full potential, but that there was becoming more scope for ergonomics with the increasing expectations of improved life quality, Pat Shipley and R. Harrison of the Department of Occupational Psychology, Birkbeck College, London, presented a broad review of the ergonomics practioner as a change agent. It was suggested that in the past the ergonomist may have too
In the installation, a press operator from the production department worked adjacent to a sorter from the quality control department who was examining products that took 2 min to pass along a conveyor before they spent some 2 or 3 hr in a Lehr.
often based his helping strategy on the politics of expertise, and a more collaborative problem solving approach was advocated. A major consideration is the status of the ergonomist, either as an internal employee or an external consultant. The level of employment may predetermine or constrain the degree of influence which can be exerted in an organisation, while the external position may effect the degree of necessary co-operation achieved.
On one cutting machine there were 19 controls positioned along its ! 8ft (5-5m) length, requiring much movement by the operator as the machine traverse the 200 yd (183 m) long face. it was noticed that some 50 yd (46 m) more operator movemerit was required when the machine traversed the face in one direction than in the other. This arose because the operators had discovered that they could steer the machine better with the stabilizer (controlled from only one end of the machine) than by using the steering controls originally placed at both ends. As a result, it is intended to place stabilizer controls at both ends. A number of recommendations had been made arising from the study, including the provision of more automatic controls, portable controls, and dual controls. Changes recommended to the nature of the job included reduced walking to the work place (it had been noted that, for example, a heart rate of 135 had been measured while the operator was getting to his work place compared with a rate of only 90 when actually at work), better provisions to enable the operator to see forward, and more training of operators to steer and prevent stalling,
Process control by man In a paper presented by G.J. Gillies of the Ergonomics Section, Pilkington Brothers Ltd, the author discussed some aspects related to an operation having the following characteristics;
4. Variable inputs of a type difficult to measure, such as material quality. 5. No precisely known model.
The author reported on three aspects of a study carried out to improve the operating performance, The first was the analysis of the operating team and work groups, Clearly, the juxtaposition at the press of an operator and an inspector from different departments created a stressful situation, particularly when the press yield became low. It was recommended that the 'hot sorter' who was carrying out the inspection on the conveyor changed his responsibility to the production department and became an assistant press operator. As a result, yields had improved. The second aspect was the use of job aids intended to create more disciplined action by the operators and to encourage them to record their actions so that recommended procedures could be put forward following an analysis of the actions. The third aspect involved the use of a computer simulation from which it was established that operators who tended to employ a large amount of control action and not wait to see the effects of any adjustment made were by the far the least successful, A further point made by the authors in discussing the conditions when press yield fell was that the natural reaction was for the operator to stand aside in favour of a more experienced operator or foreman who
could then restore the situation. This was pointed out to be a self-defeating exercise as it created a wider gulf in proficiency between the older experienced man and the usual operators, which would make itself manifest when the older employees left.
The ergonomics practioner
A warning was also given in connection with the time taken to achieve results. Diagnosis and problem solving can only proceed at a pace with which the client is happy. Time for an on-going educational process must be allowed to prevent quick solutions which ultimately fail to meet the client's real needs.
Industrial injuries The effect of experience on the incidence of industrial injuries was discussed by Dr M. Richer, following a study carried out when he was with the Department of Engineering Production at the University of Birmingham. Industrial injury rates are usually found to decrease with increasing experience, minor injuries being halved in the course of a few months and serious injuries being halved over a period over one or two years. He described a detailed study carried out from 877 production workers in 24 different jobs in a light engineering factory. Over 400,000 injury data points were involved. In general, the results showed that an
Applied Ergonomics June 1974
113
initial drop of some 30 to 40% could be expected in the first 12 to 18 months, followed by a steady decrease to about 50% of the original accident rate over the next 12 years. The analysis showed, however, that this steady long term trend was subject to a slight oscillation w i t h the accident rate peaking at about 4 yearly intervals in the case of men and at intervals of 64 months with women, The effect of age was found to be substantial, the rate being lower with increasing age, but this too was subject to a cyclical variation, the largest drop with increasing age occuring in the first, fourth, ninth and thirteenth years. It was pointed out, therefore, that any investigation into industrial injuries must take note of the effect of age and experience,
Occupational Psychology at Birkbeck College, London, carried out a study into the effects of the Aldington/Jones Committee scheme instigated in 1972. A postal questionnaire was carried out on a sample of 500 of the dockers who took advantage of the scheme, The age distribution of these showed that 43% were in their 50s and a further 43% in their 60s. Also, 43% was the number having had a length of service between 20 and 30 years, 21% having had 30 to 40 years of service and 19% over 40 years. 65% thought the scheme was either good or very good and a further 28% classified it as neither good or bad.
The docks were organised on a casual labour basis until 1967, when dockers were registered and employed by the National Dock Labour Board. The intention was that no man should be made redundant, but labour surplus to any individual employer should be employed at a reduced pay rate by'the NDLB in a manpower p o o l Within two years it became obvious that the industry was over endowed w i t h manpower due to improved cargo handling techniques and more containers, and many men
The reasons quoted for applying to take advantage of the scheme belied some of the general opinions held on dockers; 55% stated it was due to the industry declining, 37% due to work standards declining. To obtain a lump sum was the reason given by a further 37%, while other causes were: near retirement 31%, health 27%, a dislike of shift work 22%, and to obtain a better job outside the docks 18%. No less than 60% were now employed full time in outside industry and 21% were unemployed. Personal contacts proved to be the main avenue to a new job, only 22% stating that they had applied at a local employment office because they had not anticipated that exdockers would be sought after. Of those who had tried to find work, 43% had found difficulty, mostly due to being classified as too old.
were spending long periods without work on reduced wages, A number of severance schemes were started and Jennifer G. West, when a member of the Department of
Questioned o n factors underlining their choice of a new job, 57% referred to it being near home, 56% to the regular hours, 50% to the fact that it was an interesting job and 50%
Severance scheme
114
Applied Ergonomics June 1974
referred to the pleasanter conditions. Only 17% referred to its being under the control of the same union as in the docks, 12% to the fact that it was near the docks and 12% took into consideration the fact that it was an indoor job. In general, the younger people had acquired similar jobs to their dock employment, such as driving cranes or fork lift trucks, while there was a large category of 40% who had taken work as porters, messengers or caretakers etc. It was commented that this group had begun to operate a similar system to that working in the docks which, for example, created conditions whereby one or two men did not appear for work on any one while the others did their work for them. and that insistence was being made on other ex-dockers filling vacancies that arose. General comments were also invited in the survey and a great many were received, mostly lamenting the absence of some of the attractive qualities such as the comradeship of the old docks jobs and expressing a wish to return to docks work. It seemed that the severance scheme had proved an ideal solution however, for something like 60 or 70% of those taking part, although it might have been too successful in the sense that there were now too few employees and that Board was recruiting labour, it was appreciated that through the survey someone was still taking an interest in them as there was a feeling that "we were sent away with the money and they forgot about us'. Certainly, more investment advice would have been appreciated in connection with the lump sum benefit, and many people thought it would have been better to have a smaller lump sum and a larger pension.
Applying r u m r c h The opening address was given by Mr D.B. Welbourne, Vice-president for the Society for the Application of Research, and Director in Industrial C o o p e r a t i o n for the University. He discussed some aspects of getting academic research applied, pointing out that the University could probably claim the first piece of academic consultancy when in 1610 Edward Wright u n d e r t o o k the necessary mathematics to get the levelling correct when the Lee Valley water was brought into London. He spoke of the functions of the Wolfson Cambridge Industrial Unit, including the handling of enquiries from industry for advice, a situation in which often the people in industry were not aware of what help could be expected, while those in the academic world did not appreciate some of the practical aspects such as relating the expenditure of time with that of money, He regarded as very important the location of areas of research in the University that could be applied if industry and commerce would take note. One of the best ways of i 10
Applied Ergonomics June 1974
propagating the research results was to place a student in a firm or for the firm to second people to the research unit at the University from one to three years. This would enable the background thinking behind the research to be absorbed and enable industry to learn of the mistakes that had been made which, not unnaturally, were seldom published. As examples of the classical developments in this field he quoted gas turbines of the 1940s, steel work of the 1950s, the scanning light electron microscope of the 1960s and for the 1970s he forecast computer graphics applied to numerically controlled machine tools, although he did realise that their application would involve some revolutionary thinking in organisations, from the design office to the workshops.
A n t h r o p o m e t r y and design It was not inappropriate for this to be the opening session, as the first paper presented to the Society was on anthropometry. As an introduction, it was pointed out that a n t h r o p o m e t r y was a tool for the criminologist in the mid 19th century, preceding finger prints. Recently it has again become popular, for somewhat different reasons, The o p e n i ~ paper, by D. Thomson and Mrs Joan Ward, o f the University of Technology, Loughborough, covered static and functional anthropometric dimensions of British women. In particular, they were concerned with housing regulations on storage space in the home, pointing out that it should be related to the user's anthropometry. Although building regulations specify some dimensions for such factors as shelf height, for example, the illustrations show that the heights quoted refer to shelves which a given women can just reach with her finge~ tips. This is unsatisfactory as clearly the same women must be able to place and remove articles on the shelf, Similarly, body dimensions appear to be well documented. For example, there is information on forward reach in terms of the distance between the back and the finger tips. However, f o r this to be of practical value it should be related to the individual's reach over an obstruction, such as a working surface below a cupboard. A study carried out with practical conditions in mind produced data which is now
available from the Institute of Consumer Ergonomics at Loughborough. The use of figures for functional reach was important in equipment design. F o r example, reaching onto a shelf with an object held in b o t h hands showed that those with their height below the 5th percentile of the population were only able to make use of 14% of the available storage volume, while even those from the 96 to 100th percentile were only able to utilize 76-9% of the space. Some of the recommended design information was challenged. The study had shown, for example, that the height for a shelf with access over an obstruction for the lowest five percentile population should be no more than 116.1 cm, or for the highest five percentile, 163-2 cm, whereas the design bulletin recommended 170 cm. The authors pointed out that there was a notable decrease in reach with age, typical figures being the maximum heights for a shelf using an object requiring two hands of 133-2 cm for those under 60 years and ! 24.3 cm for the over 60's. It was suggested that twice the accessibility could be achieved by using pull-out storage units rather than fixed shelves. With the smaller floor space requirement, a significant monetary saving could be achieved. Anthropometri© survey Continuing the theme, Captain Nigel lnce, RAMC, at the A r m y Personnel Research Establishment, presented details of an on-going anthropometric survey of the British Army. The results of the Royal Armoured Corps part of the survey were now available from APRE at the Royal Aircraft Establishment, Farnborough, Hants. As an example of the practical aspects of the survey, he pointed out the measurement of reach, this was normally made wit h the shoulder against a wall, but in a vehicle driving situation the driver was able to lean forward against a harness thus giving an effective increase in reach. Similarly, a man's practical sitting height was normally much less than that usually measured in an upright position. Applying the data Some aspects of the application of anthropometric data to work space and equipment design were given by
C.B. Bolton of the Royal Aircraft Establishment. He spoke of a survey carried out in 1970/71 of 2000 RAF aircrew to provide information for aircraft designers and functional clothing designers. He appealed for a better presentation of anthropometric data, as the conventional percentile tables did not reveal the spread of the results. For example, a plot of stature against sitting height showed a wide
scatter, the average sitting height being achieved with individuals from 5 to 6 ft ( I "5- l "8 m) in stature. For a given leg length there could be 5 m (127 mm) variation in arm length. A convention today for aircraft cockpit work is to design for the 3rd to 99th percentile, but he showed that by considering 8 different dimensions, no less than 21 "26% of the population had to be rejected. The effects of the nature of the job should be considered when taking measurements. Rarely was it necessary to stand to attention in a cockpit but when designing for successful use of ejection seats, the b u t t o c k - k n e e c a p measurement was all important. Care must be taken when using data from obsolete surveys, and he spoke of a test rig now being used to measure recruits into the RAF, through which they would again pass at periods in their career providing an up-dating of their survey. Even short term delays, it seems, could be significant; he spoke of a weight variation of no less than 3"5 kg between morning and afternoon weighings of the same individual,
Physiological monitoring A survey on mobile cranes carried out in 1972 showed that no crane driver had worked for more than seven years at the job and that they expected to change their occupation before their 50th birthday. A further study undertaken to monitor continuously heart rate and blood pressure of a crane driver during normal working was reported by T.G. White of Glamorgan Polytechnic, and R.P. Wicks of the University of Surrey, in their paper on the continuous monitoring of physiological conditions by an electrical impedance system. Arising from a difficulty to find suitable equipment, a portable apparatus was developed following discussions with Dr David Wheipton, Principal Physicist of the Department of Medical Physics at the University Hospital (Wales), Cardiff. The noninvasive system operated on the principle of electrical impedance plethysmography. Data was obtained from eight airmen on a crane drivers course at RAF St Athan and the results reported included one subject's
heart rate reaching 130 beats per minute and another having a cardiac output of 81A litres per minute, which is some four times the normal, Although at this stage of the study it is not certain if heart rate or cardiac output can be correlated to blood pressure, it was expected that the percentage stress to which the heart is subjected should be determined and data on respiration has been observed which can perhaps be related to lung volume. A significant difference has been noticed between the results of physiological and mental stress on respiratory rhythms.
Applied anatomy Although much data has been published on the forces which humans can exert on control devices, there has been very little interest in the basic understanding of the muscle functions involved. An applied anatomical study was described by S. Pheasant of the Biomechanics Laboratory at the Royal Free Hospital School of Medicine, who introduced some views on how a knowledge of the torques a person can sustain around limb joints can effect workspace design, using as an example the driving positions of two cars currently in production, Human handedness in a paper on functional asymmetries of hand and eye, Dr G.H. Fisher of the University of Newcastle upon Tyne mentioned the frequent references to the relationship of various types of functional asymmetry. He described experiments using a stereoscope in which parts of an illusion are presented to separate eyes, to be recombined by the viewer, in a further experiment, the sides or directions of examples of functional asymmetry were observed. The results showed that the side of writing hand is related significantly to most of the activities. The results suggested that writing handedness predisposes many asymmetrical functions, that the side of dominant eye is largely irrelevant,
Sexual differences In a paper describing a theory on sex differences in information processing, and some of its possible consequences, Dr June Redgrove of Middlesex Polytechnic concluded that insufficient was known on evaluating the performance on the shop floor of men and women. She suggested that women might require a totally different approach in their work organisation. The problem was not helped by the emphasis in the related work so far carried out being on white
young military males. Furthermore, over a period of time, a job tended to be structured to eliminate those aspects at which people were less competent; thus a situation could arise where the differences between male and female performances were exaggerated if a women took over a task which over a period had been tailored to suit the capacities of a man.
Effectsof Protective clothing After pointing out some discrepancies in the percentage rest allowances made for the wearing of various types of protective clothing, N. Thomas of Glamorgan Polytechnic in his paper on psychological and physiological effects of industrial protective clothing described a study to examine the necessary allowances for recovering from the effects of wearing five given types of protective clothing, compared with ordinary clothes. Observations were taken over cycles including 20 rain work followed by 5 min rest. The results confirmed that a simple heart rate measurement gave a more accurate indication of fatigue than current work study practice relaxation allowances, but that it was necessary to relate the allowances to overall working time. The tests with the given clothing suggested that where the head has to be covered, a compressed air suit is superior to simpler assemblies with, for example, pressurized or nonpressurized respirators.
Commuter health A study on commuter travel and absenteeism carried out when he was with the London School of Hygiene and Tropical Medicine was described by Dr P.J. Taylor, now with the Occupational Health Service of the Post Office. There is a widely held view that commuting is bad for the individual's health, though it seems that there is little supporting evidence, particularly in the case of the shorter journey. Early work that had been done considered commuting in terms of journey distance and duration in relation to the time lost in travelling. By the late 1960s, there seemed to be no economic justification in expanding the London rail network. An investigation was carried out to see if any other justification existed such as the cost to the National Economy arising from commuting induced absenteeism. In general, absenteeism is estimated to cost some £1,700 million per year. A difficulty arose in obtaining a suitable unified population in central London of whom full absence records were kept. Only two organizations
Applied Ergonomics June 1974
111
with 3000 people each were located, one of which was able to co-operate, No less than 24 factors were taken into consideration, including the three regarded as most important: age, sex and status. Others included pay, race, hours of work, epidemics, geography, management attitudes, sick pay, type of journey, length of service, personality, etc.
impressed with the pilot's difficulty in operating a radio which was mounted to his left and behind him during which it was necessary to tuck the collective pitch lever (controlling the aircraft's rise or fall) under his left knee. Holding the map and the control stick in his right hand simultaneously also seemed hazardous since the aircraft was flying at about 80 knots
The median j o u r n e y time was approximately l hr, and the results showed approximately normal d i s t r ~ u t i o n , the shortest j o u r n e y being ! 2½ rain and the longest 2½ hr. Subjective assessment of comfort showed that 3-4% regarded their journeys as very comfortable, 30.5% as fairly comfortable, 35.6% regarded their travel as neither comfortable or uncomfortable, 24.4% classified it as fairly uncomfortable and 6-4% as very uncomfortable. An age relationship was apparent in that 38% of those under 30 thought it was fairly or very uncomfortable while the older people were more tolerant. Sickness absence was both more frequent and longer with those whose journey included three or more separate stages, and the figure was also higher for those who used a car for part of all of their journey. Younger people also had more time off than older, During the investigation, the nation was beset by the epedemic of 'Hong-Kong' flu which resulted in evidence that those travelling by London Transport trains had less absence than those who did not. The general conclusion was that the
at heights sometime below tree-top level, The patterns established by this technique were fairly con~stent between pilots and demonstrated that the pilot spent up to about a third of his time looking at objects inside the cockpit rather than outside, with the rather aggravating additional factor that the lower the aircraft was flying, the more was it necessary to observe instruments and other items inside the cockpit,
complexity of the journey was a more important factor than any of the others.
Helicopter pilot activity One of the most impressive presentations of the conference was made by Dr E.J. Lovesey of the Royal Aircraft Establishment, Farnborough, who presented some film taken in the course of a study of pilot activity within existing types of helicopter. Although a great deal of work has been carried out on many aspects of aviation, most of it is related to fixed-wing aircraft and very little ergonomics has been directed solely towards helicopters. His study was intended to highlight some of the problem areas now existing which could then be studied in greater detail The method adopted consisted of a cine film analysis leading to an activity chart of a pilot's head and hand movements. The camera was fitted with a very wide angle or 'fish-eye' lens. Although this produced a somewhat distorted image, even the lay observers in the audience were clearly
112
Applied Ergonomics June 1974
Power press tool setting Earlier work has been carried out on the operators' work of the power press. A further study has been made by Prof E.N. Corlett and D.I. Mercel" of the Department of Engineering Production at the University of Birmingham, with particular reference to the job of the tool setter. Such machines are running for an average of 52% of the available time, a further 10% is taken up by breakdowns and another 10% is attributed to setting time. This justifies the interest in this area. In addition, more than 50% of the accidents associated with such machines involve the setter when die changing or trying out a new die. A basic problem is the difficult access to the tool for changing the die set. Apart from a basic cleaning up operation to get access to the tool, the setter has to remove the side guards, which usually present little problem, and then the front guard, Usually it is the press user who specifies the type of guard required, rather than the machine manufacturer, a condition not always resulting in the o p t i m u m choice of guard. Front guards may be side hung, pivoting to one side, in which case frequently some controls are isolated when the guard is moved aside, or up swung when it is pivoted upwards and held open by a hook. With presses of more than about ! 0 tons capacity, to do this it is usually necessary to stand on a box, obtain the assistance of a second setter, or use some form of pulley arrangement, Before removal it is necessary to close the die, but only two manufacturers provide efficient stroke and position indicators. Before extracting the top tool, it is necessary
to remove the ram cap and a typical problem here is the need to undo three bolts which are so close together that only about a quarter turn movement can be obtained before changing the position of the spanner. The lower tool is often placed too low for a good view to be obtained. It was observed that setters, when required to exert a pulling action on a bolt, tended to use both hands on the spanner, increasing the likelihood of slipping on a greasy floor. Moreover, setters are required to provide their own tools and consequently tend to use the cheaper open-ended spanners and not the safer ring type. The press fly wheel guard panel is usually fixed by six Philips head screws, and having been once removed is seldom replaced. Only one manufacturer fits wing nuts as an encouragement to refitting. The authors suggested that an improvement could be effected if presses were fitted with a system permitting the press to be "jogged' when the guards had been removed, as this would save considerably in setters' time. Once the press has been placed at top-dead-centre, the die set has to be pulled out onto an adjustable-height platform o n a trolley. This usually requires the assistance of a second setter, who is thus disturbed in his own work with consequent potential dangers when he returns to his own job. The setter has to compare the new shut height of the die set with the old die shut height which he had to note in the first place and has subsequently remembered. None of the firms at which the study was carried out provided steps for setters working at controls and adjustments high above the ground, and the use of old boxes and oil cans produces some spectacular falls. Only one manufacturer fits a 'daylight' indicator, ie, a guide to the distance between the ram face and the press plate, which should equal the shut height of the t o o l With most manufacturers, the data required when making adjustments following tool changing was provided on a legend plate which was not mounted where it could be seen when the adjustments were actually being made. An analysis of the setters' discomfort complaints showed that the most common stress areas were the neck, shoulders, fore-arm and lower back. Mining systems An investigation into the design of the system at the coal face was
reported by A.A. Knight, J.W. Murphy, B. Ward and M. Attfield of the Institute of Occupational Medicine, Edinburgh. After outlining the development of the existing systems they referred to a detailed ergonomics study which was started in 197 i, concentrating on mining machine operators with the three aims of making the men's task more congenial, especially in thin seams, of insuring
1. Many controls, some interacting with each other in their effect, 2. Long time lags, of the order of minutes rather than seconds, between the action and its effect, 3. Numerous output variables to control
that they can perform efficiently with the equipment, and that the men's performance did not impede the performance of the system. Slides emphasised the very difficult conditions in which the miners operated the machines in thin seams from a kneeling position. Frequently the miner had to lean over the machine to use the controls. Whilst this was not difficult if there was adequate headroom, this was not the case in the thinner seams, especially since rocks travelling along the conveyor under the machine had been k n o w n to lift the machines up against the roof of the s e a m .
Ergonomists were interested in such processes because they relied heavily on the skill of the operator in the control and because of the long time required for the operators to obtain the necessary degree of skill for proficient operation. In such systems in industry, the cost of mistakes could frequently be very high, possibly involving a loss of whole shift. The example he used to illustrate his points taken from the glass industry was glass pressing. In the case of colour TV ware, the yield from presses was only of the order of 45%.
Starting with the premise that the contribution ergonomics had actually made to the solution of human problems at work had fallen somewhat short of its full potential, but that there was becoming more scope for ergonomics with the increasing expectations of improved life quality, Pat Shipley and R. Harrison of the Department of Occupational Psychology, Birkbeck College, London, presented a broad review of the ergonomics practioner as a change agent. It was suggested that in the past the ergonomist may have too
In the installation, a press operator from the production department worked adjacent to a sorter from the quality control department who was examining products that took 2 min to pass along a conveyor before they spent some 2 or 3 hr in a Lehr.
often based his helping strategy on the politics of expertise, and a more collaborative problem solving approach was advocated. A major consideration is the status of the ergonomist, either as an internal employee or an external consultant. The level of employment may predetermine or constrain the degree of influence which can be exerted in an organisation, while the external position may effect the degree of necessary co-operation achieved.
On one cutting machine there were 19 controls positioned along its ! 8ft (5-5m) length, requiring much movement by the operator as the machine traverse the 200 yd (183 m) long face. it was noticed that some 50 yd (46 m) more operator movemerit was required when the machine traversed the face in one direction than in the other. This arose because the operators had discovered that they could steer the machine better with the stabilizer (controlled from only one end of the machine) than by using the steering controls originally placed at both ends. As a result, it is intended to place stabilizer controls at both ends. A number of recommendations had been made arising from the study, including the provision of more automatic controls, portable controls, and dual controls. Changes recommended to the nature of the job included reduced walking to the work place (it had been noted that, for example, a heart rate of 135 had been measured while the operator was getting to his work place compared with a rate of only 90 when actually at work), better provisions to enable the operator to see forward, and more training of operators to steer and prevent stalling,
Process control by man In a paper presented by G.J. Gillies of the Ergonomics Section, Pilkington Brothers Ltd, the author discussed some aspects related to an operation having the following characteristics;
4. Variable inputs of a type difficult to measure, such as material quality. 5. No precisely known model.
The author reported on three aspects of a study carried out to improve the operating performance, The first was the analysis of the operating team and work groups, Clearly, the juxtaposition at the press of an operator and an inspector from different departments created a stressful situation, particularly when the press yield became low. It was recommended that the 'hot sorter' who was carrying out the inspection on the conveyor changed his responsibility to the production department and became an assistant press operator. As a result, yields had improved. The second aspect was the use of job aids intended to create more disciplined action by the operators and to encourage them to record their actions so that recommended procedures could be put forward following an analysis of the actions. The third aspect involved the use of a computer simulation from which it was established that operators who tended to employ a large amount of control action and not wait to see the effects of any adjustment made were by the far the least successful, A further point made by the authors in discussing the conditions when press yield fell was that the natural reaction was for the operator to stand aside in favour of a more experienced operator or foreman who
could then restore the situation. This was pointed out to be a self-defeating exercise as it created a wider gulf in proficiency between the older experienced man and the usual operators, which would make itself manifest when the older employees left.
The ergonomics practioner
A warning was also given in connection with the time taken to achieve results. Diagnosis and problem solving can only proceed at a pace with which the client is happy. Time for an on-going educational process must be allowed to prevent quick solutions which ultimately fail to meet the client's real needs.
Industrial injuries The effect of experience on the incidence of industrial injuries was discussed by Dr M. Richer, following a study carried out when he was with the Department of Engineering Production at the University of Birmingham. Industrial injury rates are usually found to decrease with increasing experience, minor injuries being halved in the course of a few months and serious injuries being halved over a period over one or two years. He described a detailed study carried out from 877 production workers in 24 different jobs in a light engineering factory. Over 400,000 injury data points were involved. In general, the results showed that an
Applied Ergonomics June 1974
113
initial drop of some 30 to 40% could be expected in the first 12 to 18 months, followed by a steady decrease to about 50% of the original accident rate over the next 12 years. The analysis showed, however, that this steady long term trend was subject to a slight oscillation w i t h the accident rate peaking at about 4 yearly intervals in the case of men and at intervals of 64 months with women, The effect of age was found to be substantial, the rate being lower with increasing age, but this too was subject to a cyclical variation, the largest drop with increasing age occuring in the first, fourth, ninth and thirteenth years. It was pointed out, therefore, that any investigation into industrial injuries must take note of the effect of age and experience,
Occupational Psychology at Birkbeck College, London, carried out a study into the effects of the Aldington/Jones Committee scheme instigated in 1972. A postal questionnaire was carried out on a sample of 500 of the dockers who took advantage of the scheme, The age distribution of these showed that 43% were in their 50s and a further 43% in their 60s. Also, 43% was the number having had a length of service between 20 and 30 years, 21% having had 30 to 40 years of service and 19% over 40 years. 65% thought the scheme was either good or very good and a further 28% classified it as neither good or bad.
The docks were organised on a casual labour basis until 1967, when dockers were registered and employed by the National Dock Labour Board. The intention was that no man should be made redundant, but labour surplus to any individual employer should be employed at a reduced pay rate by'the NDLB in a manpower p o o l Within two years it became obvious that the industry was over endowed w i t h manpower due to improved cargo handling techniques and more containers, and many men
The reasons quoted for applying to take advantage of the scheme belied some of the general opinions held on dockers; 55% stated it was due to the industry declining, 37% due to work standards declining. To obtain a lump sum was the reason given by a further 37%, while other causes were: near retirement 31%, health 27%, a dislike of shift work 22%, and to obtain a better job outside the docks 18%. No less than 60% were now employed full time in outside industry and 21% were unemployed. Personal contacts proved to be the main avenue to a new job, only 22% stating that they had applied at a local employment office because they had not anticipated that exdockers would be sought after. Of those who had tried to find work, 43% had found difficulty, mostly due to being classified as too old.
were spending long periods without work on reduced wages, A number of severance schemes were started and Jennifer G. West, when a member of the Department of
Questioned o n factors underlining their choice of a new job, 57% referred to it being near home, 56% to the regular hours, 50% to the fact that it was an interesting job and 50%
Severance scheme
114
Applied Ergonomics June 1974
referred to the pleasanter conditions. Only 17% referred to its being under the control of the same union as in the docks, 12% to the fact that it was near the docks and 12% took into consideration the fact that it was an indoor job. In general, the younger people had acquired similar jobs to their dock employment, such as driving cranes or fork lift trucks, while there was a large category of 40% who had taken work as porters, messengers or caretakers etc. It was commented that this group had begun to operate a similar system to that working in the docks which, for example, created conditions whereby one or two men did not appear for work on any one while the others did their work for them. and that insistence was being made on other ex-dockers filling vacancies that arose. General comments were also invited in the survey and a great many were received, mostly lamenting the absence of some of the attractive qualities such as the comradeship of the old docks jobs and expressing a wish to return to docks work. It seemed that the severance scheme had proved an ideal solution however, for something like 60 or 70% of those taking part, although it might have been too successful in the sense that there were now too few employees and that Board was recruiting labour, it was appreciated that through the survey someone was still taking an interest in them as there was a feeling that "we were sent away with the money and they forgot about us'. Certainly, more investment advice would have been appreciated in connection with the lump sum benefit, and many people thought it would have been better to have a smaller lump sum and a larger pension.