Driving Ability

Over time, one may expect to experience weaker (or somewhat diminished) physical, perceptual, and cognitive function. These changes, which can occur as early as age forty, include reduced capacity of vision at night and weaker contrast sensitivity, which makes signage along roadways more difficult to read. Most people also experience an increased sensitivity to glare during night driving, and many have difficulty recovering from bright lights. Hearing loss usually accompanies aging. Most people compensate for both visual and auditory changes as they happen, and do not realize that their abilities have declined over time.

Decreased strength and flexibility also typically accompany aging. While these may be offset with regular exercise and strength training, most people exercise less frequently as they age, when they should be exercising more to compensate for weakening muscle and bone mass. These problems lead to more problematic neck and Figure 1 Age-related changes in different parts of the information processing system. SOURCE: Based on data from: Wickens, C. D. Engineering Psychology and Human Performance. New York: Prentice Hall, 1993. trunk rotation, in addition to difficulty accessing a vehicle or turning the head to compensate for natural blind spots in the car to view oncoming traffic or pedestrians. For some, these physical changes may contribute both to a reduced desire to travel and more difficulty in concentrating on the entire situation of driving. The speed with which most people perform routine and simple tasks slows as they age because movement is more difficult as muscle strength and flexibility decrease.

Individual perceptions change over time as well. For example, some research indicates that capacity for judgment of velocity and distance of approaching vehicles becomes reduced with age. This judgment is a crucial component in the driving process, and when it is impaired it may cause an accident. The driver who cannot accurately determine the distance and speed of an oncoming vehicle risks an accident when making a left turn at an intersection.

People begin to react more slowly to stimuli as they age because response times begin to slow. While driving, a split-second decision can be the difference between an accident and a close call. Reaction time is an important feature of driving because a driver must see a problem, think about it, and then react—apply the brake, steer, or take another action as necessary. As shown in Figure 1, attention is made up of many linear subtasks that lead to action. The stimulus affects the sensory processes in the brain, which affect perception, information processing, and response, all of which are key components of attention. The longer it takes for each response, the longer it takes for the intended action. This leads to problems concentrating on the many subtasks that must be considered while driving. Synthesizing multiple pieces of information and conducting the many actions of driving may sometimes overwhelm the older driver who cannot react quickly to a stimulus.