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Ergonomics is organized mismon sense

21st May 1971, Page 70
21st May 1971
Page 70
Page 71
Page 70, 21st May 1971 — Ergonomics is organized mismon sense
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Which of the following most accurately describes the problem?

Mastering and retaining sldlls; the special needs of the elder driver; possible health hazards from noise and vibration; the 'energy drain' of heavy steering

"BECAUSE of the application of ergonomics to commercial vehicles, younger men will become safe, skilled drivers more quickly than their predecessors," says Dr E. J. Hamley, reader in human biology at Loughborough University of Technology. "They will have a longer expectation of life and their lives will be happier.

"Ergonomics is the study of the human at work, with or without a machine, in an environment. Basically it is organized common sense and like common sense it relates to responses that are subjective as well as to intentions that are objective and takes into account the extent to which forms of control promote skill or condition it.

"Matching the machine to a man individually may depend on the kind of machine to which the man had to match himself in the past and the length of time he was associated with the same type of machine."

Dr Hamley has made a number of studies of the human at work in the environment of a commercial vehicle. And his comments on some aspects of ergonomics are a lead-in to what he describes as the four ages of man.

The conclusions that can be drawn from outlining these ages are of special importance in considering the case of the older, experienced man with a good record and his adaptability to a new and improved environment. This is all-important. The young driver has the prospect of a longer, happier working life but the population is ageing, and a man may be categorized as older and experienced at the age of 40 or less.

if a child, who has just learned to walk, sets himself (or herself) the target of walking across the room without falling, his brain is completely preoccupied with the exercise and every muscle in his body is used in the attempt. The child employs his brain power and muscles wastefully and is tired out after walking a distance that would require a fraction of the total energy actually expended if the available energy had been used economically. He is in the first age of man; he is still learning his most simple skills.

When a human has learned to economize

is energy and to matdh effort to the effort ceded to complete a piece of work he has a !serve of energy to cope with non-routine vents and emergencies. In due course he rill achieve "total experience" in that he will ave attained a high degree of skill which ould only be improved marginally by arther experience, But, and this is a big but, e has not lost flexibility in adaptation to ew situations that affect control of the lachine and to a new machine having haracteristics that are different from he one that is familiar to him. At this tage, he is in the second age of man; [e is learning complex skills.

In the third age of man, the human is still mater of his skills but has lost flexibility. kpplying his skills to a different type of nachine takes a longer time than is required oy a man in the second age.

Ireater skill For example, an older driver of a ornmercial vehicle may have developed ;reater skill than a younger man and may wentually be able fully to apply his skill to he handling of a new type of vehicle. But awareness of his deficiency in comparison with the younger man may undermine his confidence and if he has an accident, even a in nor one, early in his handling of the new vehicle he may take a long time to regain his confidence.

Another way of looking at this is that he nust be given sufficient time by his employer to adapt himself to his new machine. When this is not done a top-class driver may be lost to the industry. Understanding advice from the fleet manager and a refresher course could well have given him a new lease of usefulness covering a period of many years.

Energy wasted Dr Hamley emphasizes that a non-flexible driver who is learning new techniques wastes energy like the human in the first age of man and his reserve of energy may be quickly used up. In other words, he feels tired quickly. For this reason an older driver at the wheel of an older vehicle may in practice be a better and safer driver than a younger man handling a newer, more easily controlled, ergonomically conditioned vehicle.

In the fourth age of man, the man's skills are much reduced and his abilities to relearn may now be very limited. This is the man who has long earned his retirement or is beset by severe physical illness.

• Dr Hamley observes that there are "huge differences in the physical and psychological components" of human beings that invalidate an exact comparison of two or more humans based on age, notably with regard to the age that a human moves from category two to category three. Advances in the technology of measuring energy depletion when a driver is, exposed for long periods to a fatigue-producing environment have been slow.

Depletion of physical and mental energy could, for example, be reduced by fitting an automatic or easy-change transmission, the psychological strain of • sorting out the gears to the best advantage for performance and safety being more serious in many cases than the physical strain of frequent manipulation of the gears.

Ease of steering is particularly mentioned by Dr Hamley as a means of reducing the work load on the driver and the rate of energy depletion. He regards servo steering as essential for heavy vehicles and believes that smaller steering wheels would be benificial if used in conjunction with a servo mechanism. Steering, seating and vision should always be considered together.

The skill of a driver is closely related to the posture in which he learned his skill, and any variation can upset his ability to co-ordinate his faculties. This is particularly true in the case of a bus being driven over the same routes day in, day out. Dr Hamley cites the notable case of a fleet of buses that had to be refitted with a less comfortable and less "suitable" seat because an "improved" seat upset the "sighting ability" of the older drivers.

Great disadvantage

The heavy vehicle driver is at a great disadvantage to the car driver, says Dr Hamley, because frequently he is handling a vehicle that can be compared ergonomically to cars of the 1928/1932 era but travels at the same speeds as cars do over a major part of the total mileage covered. The inferior suspension of commercial vehicles when running light, and the practical difficulties of compensating adequately for unsatisfactory suspension is a serious deficiency that is related to the "destructive" effects of certain vibration frequencies on the human frame and on human faculties. The inferior adhesion properties of some commercial vehicles' tyres in the wet compared with the properties of tyres now fitted to the majority of cars is also a deficiency which could be a constant strain on the driver and which increases the hazard factor. The general use of radial tyres would materially reduce the difference between the brake, efficiencies of heavy commercials and. cars.

Vibration problem In Dr Hamley's view, the extension of motorways and the operation of vehicles at a sustained speed for long periods that running on a motorway involves, has exacerbated the vibration problem. Human organs might well react to sustained vibration in the same way as the body structure of a vehicle or aeroplane.

A structure may have an indefinitely long life under normal operating conditions during which resonant frequencies are transient or cyclical. But a critical frequency that is sustained over long periods can result in early fatigue fracture of the structure or a component of the structure. Complete or partial damage to parts of the body may also result from long exposure to a vibration of critical frequency.

Farm tractors are regularly driven over long periods with the engine operating at the same speed and producing vibrations of unvarying frequency. And in addition there are many cases where the noise of the tractor with a vertical exhaust pipe has caused injury to the ear and hearing sensitivity of the tractor driver, which would not have occurred if the engine speed had been varied from time to time and the exhaust system had been better designed and silenced.

The intensity of a noise (that can be measured in dB on a meter) is not necessarily indicative of its harmful properties, which may be derived from certain component frequencies. Eliminating one or more frequencies could, in Dr Hamley's opinion be as beneficial to the driver as a big reduction in noise intensity.

Extended research There is need for extended research into many aspects of vibration phenomena. Continuous vibration might well affect the composition of the blood. Very interesting information showing a possible connection between exposure to continuous vibration and changes in the contents of certain factors in the blood is now becoming available. A large research programme will • be needed to show the extent to which these changes may be dangerous to health and it may be that in certain eases even a simple change of diet might be used to help restore the body to its normal condition.

Dr Hamley agrees with Dr Fogg of BLMC and other authorities that noise is also a subjective experience. A certain kind of noise can increase the rate of energy depletion of one human and have little effect on another but—Dr Hamley emphasizes—the time has come for the responses of the individual to noise as well as non-audible vibrations to be analysed individually. The more experienced a driver the more useful he is to the community and the more likely is it that corrective measures are necessary to perpetuate his usefulness.

Ventilation is also'of top importance. The rate of air flow through the cab should match the humidity, a greater flow being , required in the case of high humidity. A driver tends to become sleepy if air flow is inadequate and even if sleepiness does not prevail, this condition impairs concentra tion. Air outlets shOuld be provided behind the driver. Lowering the window for this purpose can produce draughts round the driver's head that are detrimental to his physical well-being.

Any road user will surely agree with Dr Hamley that the ability of a driver to `:switch off anger" is a particularly valuable asset in the interests of safety particularly in the case of a driver in the "angry young man" category. Apparently the effect of anger is also to cause changes in the bloodstream which in some people take longer to return to normal than in others. In many cases this improves as people grow older and literally learn to control their anger better. And Dr Hamley suggests that it would be a help to the professional driver if it were-possible to discover how to teach drivers to achieve this control quickly and use the wasted energy spent for anger in another more useful way such as to delay fatigue.

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