Auto safety and human adaptation

Issues in Science and Technology, Winter 2000/2001 by Smiley, Alison

Vehicle manufacturers around the world are spending large sums of money to develop sophisticated new safety devices. Anti-lock brakes were one of the first. Within the next 5 to 10 years, adaptive cruise control, collision warning, and vision enhancement systems are expected to become standard features on new cars, all in the name of safety. Governments, especially in Japan, Europe, and the United States, are contributing research funds for the development of these devices. Safety is the stated goal, but clearly economics is a major driving force. These devices will intrigue and attract car buyers.

Expectations for improved safety are high. But they may not be met if the human penchant to adapt is ignored. Take vision enhancement systems as an example. These systems use thermal imaging and a heads-up display to enhance the driver's view of the central part of the road scene, allowing drivers to more easily spot pedestrians and animals on the road at night. Such a system was first available in the United States on the 2000 model year Cadillac deVille. Such systems ought to improve safety but may not if they prompt people to drive more frequently in low-visibility conditions. There is already good reason for skepticism. Anti-lock brakes were expected to significantly reduce crashes. These devices work by sensing lockup and releasing the brake before applying it again: the same thing a driver does when pumping brakes but far more rapidly. By these means skidding is prevented and steering control is maintained. But as large studies have shown, they have not had a demonstrable effect on overall crash rates. Drivers appear to have changed their behavior in ways that reduced or eliminated the safety cushion provided by the improved braking.

Because we expect so much of these devices and because of their cost, it is time for governments and vehicle manufacturers to examine more fully the nature of driver adaptation and its effects. If policymakers truly want to improve safety, they must ensure that the research involved in developing and implementing these devices is comprehensive in its analysis of the human element. It is not enough to develop a better device; one has to know how humans interact with it.

There is also the issue of whether drivers will grasp how these devices function. Some of the limitations of the new systems are subtle. For example, adaptive cruise control, which is being introduced as an option on this year's European Jaguars and Mercedes, maintains a selected speed but also senses slower-moving vehicles ahead and responds to them by slowing the vehicle. However, because of technical limitations, it will not respond to stopped vehicles, which may result in an unpleasant surprise for the uninformed driver. A safety system that is poorly understood by the user isn't an improvement; it's a liability. Governments and vehicle manufacturers should consider the need for some form of education for drivers of these increasingly sophisticated vehicles.

Pervasiveness of adaptation

Although the aim of high-tech devices is to improve safety, the human proclivity for adaptation makes this a challenge. Adaptation, defined as the process of modifying to suit new conditions, is an everyday occurrence in driving and happens on many levels. Short-term adaptations occur when we are pressed for time and take a chance on running a red light. Long-term adaptations occur as we age. Older drivers reduce their speed by a few miles per hour on average and allow longer headways to vehicles in front.

We adapt our focus of attention to the specific driving task. Eye-movement studies of drivers show a dramatic narrowing of eye fixations when drivers are closely following another vehicle. Drivers in heavy traffic reduce by 20 percent the length of time that they spend glancing at the car radio while operating it, as compared to when they drive in light traffic. Adaptations also occur in response to the roadway environment. A change in traffic signals to provide an all-directions red light clearance interval will increase the numbers of drivers who enter the intersection during the caution period. Increasing the lane width, widening the shoulder, and resurfacing the roadway all result in higher speeds.

Adaptations also occur in response to vehicle changes. Changes that occurred before the advent of high-tech devices probably resulted in various adaptations. For example, the installation of turn signals inside the vehicle may have increased the likelihood of drivers signaling, especially in inclement weather. Automatic transmissions have accelerated the learning process for novice drivers, who no longer have to deal with shifting gears while controlling vehicle speed and lane position. In Canada, a standard driving course is 18 lessons for those learning on standard and 13 for those learning on automatic transmissions. Power-assisted brakes must have allowed drivers to approach situations requiring a stop at higher speeds. Improved car handling is thought to be one of the elements behind continual increases in average speed during the past 20 years.