Warren, Mich. — ``Most people think they're freaks when they step out of the anthropometer,'' explains T. J. Kuechenmeister, head of the human-factors laboratory here at the General Motors Technical Center. ``People often think of themselves as small, large, or average, but that's just not true,'' Mr. Keuchenmeister asserts. ``We're really made up of all different body-size segments. There really is no small person, big person, or average person,'' he says -- which is why the auto industry finds it hard to produce cars that ``fit'' every buyer.
The anthropometer is a chairlike device which permits a dozen different body measurements to be taken, among them upper-leg length, seat length, hip width, forearm length, and knee height.
The goal of the human-factors engineer is ``to make as large a percentage of consumers as comfortable as possible,'' according to Lyman M. Forbes of Ford Motor Company, who explains that automakers design for the 95th percentile, which means that 95 percent of all adults fall below that figure in size.
Mr. Forbes, a psychologist, says that ``if a big man is having trouble with the bottom of the steering wheel rubbing his thighs, then you say, fine, we'll move the steering wheel up and take care of the 99th percentile. But immediately you find that the small person can't see over the top of the steering wheel. We run into that type of thing all the time. We're looking at virtually everything about drivers and how they use their cars.''
Trevor Creed, a longtime Ford designer now with Chrysler, explains: ``We try to position the controls where they are ergonomically sound.''
Ergonomics extends not only to the visual, tactile side of things (switches and clear legibility of the instrumentation), but also to the relationship to the human body of such things as the armrests on the doors, the shape of the seat, and whether you can reach things easily and without confusion.
``It requires that somebody sitting in the vehicle for the first time can orientate himself to where everything is so that he doesn't have to hunt to find the switches, and that the functions operate in a predictable manner and are not too complicated,'' says Mr. Creed.
Among other things, the human-factors people are concerned with response times, error rates, and eyes-off-the-road time.
Many motorists might dispute the success of the interior designers' positioning of dials and controls. Obviously, the human-factors specialist is but one voice among many in the design of an automobile. Designing a car is a series of trade-offs and compromises between engineers, marketing people, designers, and management.
Also, motorists themselves share some of the blame. ``What people tell us they would like to have in their car is not necessarily what would be the very best from a human-factor point of view,'' says Keuchenmeister.
Car buyers, for example, have asked for better radios, but now complain about the complexity of the radios. At one time, people were satisfied to have an on/off volume-control knob, tuning knob, and a series of preset stations. Then the aftermarket companies began to sell a better radio than the original radio which the manufacturers installed. The carmakers had to follow suit.
Color is extremely important to the ergonomics specialist, but, warns GM's Kuechenmeister, ``you can overdo color.'' What color is best? ``It differs by person and age,'' he responds. ``We recommend the middle wavelengths, not the extreme wavelengths, ranging from the tail end of the blue into the yellow. Color can make a person feel agitated.''
Digital instrumentation is expected to grow, car designers agree. ``From a performance point of view in our testing, we've found that driver performance is identical for the two systems of speedometers, digital and analog,'' notes the GM specialist. ``You can have bad digital gauges as well as bad analog gauges,'' observes Mr. Forbes of Ford.
To reduce glare, the auto industry is turning to anti-reflective coatings as well as positioning in order to minimize the effect of glare. As cars got smaller in the 1970's and '80's, car buyers still wanted sufficient inside space. In response, the designers pulled the instrument panel farther forward. Also, as cars got smaller they tended to get more aerodynamic, with windshields that had a sharper angle. All of this contributes to glare.