In our society, there is a big emphasis on autonomy and mobility. It is therefore not so surprising that our society is dependent on automobiles and recent studies have shown that individuals maintain active driver status and stay on the road later into life. There are more drivers over the age of 65 than ever before, and this number will probably keep growing. A high age and age-related cognitive conditions negatively affect the visual, cognitive and physical abilities that are necessary for safe driving. Clinicians are often called upon to comment on an older patient’s ability to remain active drivers. Ceasing driving can have negative ramifications on everyday activities, like social activities and getting to work. It also has a negative effect on the sense of autonomy and it’s also associated with poo health and depression. It’s difficult to evaluate the safety of the older driver in society, while trying to balance the person’s need for mobility and quality of life.

Driving research

According to research, the relationship between driving performance and driving outcome can be conceptualized as a triangle or iceberg. At the top of the iceberg are driving errors that produce accidents, like running a red light. The bigger middle part consists of less obvious driving errors. These driving errors can increase crash risk or result in near crashes. The bottom of the triangle or iceberg is the optimal driving section. There are two main areas of driving research that have evolved in investigating driving errors. The first tries to figure out the relationship between specific driving errors of different severities and crash involvement. The second tries to understand driver characteristics that are related to a high likelihood of committing driving errors. For clinicians who deal with older people, it is important to understand how age and cognition contribute to these driving errors.

In driving research, it is important to look at the variability in how driving outcome or driving performance is defined in the laboratory. This behaviour is often not defined in the same way. Most studies define driving performance in the following way: behind the wheel examination, performing on driving simulators, performance on instrumented vehicles, self-reported driving behaviours, documented crash involvement or crash statistics. There are significant differences across these methods. The behind-the-wheel examination is the most clinically useful method of evaluating driving performance. It is an on-road evaluation conducted by a driving specialist in a dual-controlled vehicle. Together with the driving specialist’s off-road clinical evaluation, it compromises a clinical driving evaluation. Behind-the-wheel examinations vary, because there are no mandatory rules or guidelines. In most of the cases, the person being evaluated is guided through identified routes and his/her driving behaviours are observed. There are two types of studies done in driving research. The first type are the studies conducted with a clinical focus and the second are studies conducted with a transportation research focus. These two areas should inform each other, but they often don’t. most of the research is done by transportation researchers and it is typically not published in journals that are accessed by clinicians.

Characteristics of health older drivers

There is a misconception about older drivers and the misconception is that older drivers are more often involved in automobile crashes compared to other age groups. However, empirical data does not support this claim. Some studies even show that older drivers have lower crash rates than all other age groups. What research did find, is that crash risk increases as driving exposure (annual miles driven) decreases. Older people who drive less than 2000 miles annually, which is approximately 13% of the older drivers, have one of the largest crash rates. Older adults are also more likely to be involved in certain types of crashes compared to younger and middle-aged drivers. Studies show that drivers aged 65+ are more likely to be involved in crashes at stop signs, intersections, changing lanes and while turning.

Driving errors

Studies have shown that high crash rates at intersections controlled by a stop sign were noted in older drivers (age 65-80) and younger drivers (18-21) who were more likely to run stop signs, compared to middle aged drivers. Older drivers seem to show a dangerous braking profile compared to middle age adults. The older adults brake suddenly. They begin breaking closer to the stop sign and progress faster from the initial brake press to maximum breaking. This results in a short stop. Errors in judgment and/or attention are also related to increased crash risk in older drivers while changing lanes. According to studies, crashes that occurred when the driver field to yield the right of way increased with age and they occurred more often when the driving was turning left. Many old drivers fail to evaluate the correct speed of the oncoming vehicle. The oldest drivers fail to see some vehicles.

Studies show that different cognitive abilities are associated with different driving performance measures in healthy older people, who do not have a cognitive impairment. Research has shown that older adults make certain errors more often than other drivers, such as speed control, lane changes, parallel parking and starting the car and pulling away from the curb. Older adults also committed more high crash-risk driving errors than middle-aged drivers. Older drivers often fail to check for traffic before changing lanes. Older adults are also more susceptible to distraction. Many studies have also shown that when the executive functions of the older adults are intact, they are less likely to make driving errors.

Driving in older adults with neurological diseases

Early work suggested that older people with Alzheimer’s Disease had an increased risk of crashes compared to age-matched controls, but recent studies have found no relationship between dementia and crash risk. Crash rates may not differ between health older people and people with Alzheimer’s Disease, but these two groups differ on driving errors committed. One studied showed that people with Alzheimer’s Disease only made more errors in lane changes. One big study that tested drivers with the behind-the-wheel examination, showed that increased age, greater severity of dementia and lower education were associated with higher rates of behind-the-wheel failure. Only 22% of people with Alzheimer’s Disease failed the exam. So, despite the evidence that older drivers as a group commit more high crash-risk driving errors than health people do, many older drivers with Alzheimer’s Disease are able to maintain safe routine driving over several years. However, the ability of drivers with Alzheimer’s Disease to adapt to novel driving situations is compromised compared to older adults without this neurocognitive condition. Other studies have found that cognitive performance, working memory and verbal fluency are related to crashes. People with Alzheimer’s Disease were also found to be more likely to engage in sudden vehicle slowing, which increases the risk of being struck from behind. Sudden slowing was associated with multiple cognitive abilities, but executive functioning was associated with the greatest increase in risk of unsafe behaviour.

Drivers with Parkinson’s Disease

Evidence suggests that older adults with Parkinson’s Disease are more likely to commit certain driving errors than healthy older adults. These errors involve lane changes, backing out of space, not checking the blind spot, indecisiveness at intersections and reduced use of rear- and side-view windows. Drivers with Parkinson’s Disease committed more errors than healthy people when turning, maintaining lanes or at stop signs. They also committed more safety errors according to a big study, but they did not commit more high-crash risk errors. Most people with Parkinson’s Disease are able to pass clinical driving evaluations. The drivers with Parkinson’s Disease do not limit their driving and they make as many miles a week and drive as many times as healthy adults do. When looking at cognitive measures, the drivers with Parkinson’s Disease who are seen as safe, do not differ cognitively from healthy drivers. Drivers with Parkinson’s Disease who were seen as marginally safe, performed worse on measures of verbal learning and memory, working memory, finger tapping and visuospatial ability than healthy drivers did. These results show that working memory and visuospatial abilities are important for safe driving. Studies have also shown that disease duration and severity have a negative impact on driving performance (longer duration and severity, more errors). Also, contrast sensitivity (the ability to see objects that do not stand out from the background) has a negative effect on driving safely (lower sensitivity, more errors).

Older drivers with mild cognitive impairment

There is not so much research on the driving performance of older people with mild cognitive impairment as is on drivers with Alzheimer’s Disease and Parkinson’s Disease. One looked at older drivers with mild cognitive impairment and five error types: steering steadiness, turning, gap judgment, lane control and maintaining proper speed. There was also a control group of healthy adults. The results showed that the overall mean errors did not differ between adults with mild cognitive impairment and cognitive healthy older people. The drivers were also judged by a driving specialist and when the groups were compared on the ratings of this specialist, a higher proportion of adults with mild cognitive impairment were judged as showing not optimal performance on left turns, overall driving performance and lane control. The driving performance of people with mild cognitive impairment was less than optimal, but these individuals are not impaired. There were no drivers who were seen as unsafe drivers. The researchers of this study suggest that drivers with mild cognitive impairment don’t perform optimal, because their executive functions are slightly impaired.

Application to clinical neuropsychology

Clinical neuropsychologists are often asked to comment on the driving abilities of older adults. It is quite a responsibility to decide whether somebody is able to drive or has to stop driving. It is difficult for clinicians to translate the statistically significant relationships between cognition and driving into clinically meaningful outcomes for older people. There are no guidelines as to what constitutes a sufficient assessment battery for determining driving fitness. Researchers urge clinicians to consider risk factors for decreased driving ability and to use informant report as an important method in determining the risk of the older patient with dementia. The writers think that neuropsychological assessment can make a great contribution to clinical driving evaluations. Also, if it’s possible, a cognitive assessment should be included in the driver evaluation process. The clinical driving evaluation is the gold standard for driving assessment. Driving simulation is of great use, but it’s not really a good clinical tool. It is important to remember that what constitutes a sufficient clinical neuropsychological evaluation may not constitute adequate neuropsychological assessment in driving ability. Research needs to provide direction for the selection of neuropsychological measures that need to be administered. Some domains associated with driving performance have been identified in the literature and some of these are attention, reaction time, judgment, inhibition, working memory and spatial perception.