It is well documented that older drivers have to cope with declining vision and exhibit poorer performance on a wide range of tests of perceptual and motor ability and response speed (see for example Ysander and Herner, 1976). Ranney and Pulling (1990) found that older drivers (74-83 years of age) score lower on laboratory tasks requiring rapid switching of attention. Rackoff and Mourant (1979) reported poorer performance of older drivers on motor tests and especially on the embedded figures test.
Yet the accident rate of elderly drivers is lower than expected on the basis of the skill model, although the fatality amongst elderly drivers is quite high due to their physical frailness (Evans, 1988; Brouwer, 1989).Hakamies-Blomqvist (1994) found that older drivers had fewer accidents at nighttime and under bad weather and road-surface conditions compared to younger drivers. Older drivers were also less often in a hurry, alcohol intoxicated or distracted by non-driving activities compared to younger drivers. These results were interpreted as evidence that older drivers avoid more difficult conditions. Ranney and Pulling (1990) reported that complex traffic situations pose problems for elderly drivers. They are more often involved in multiple vehicle intersection accidents, while they are less involved in single-vehicle accidents. They questioned the idea that older drivers have higher accident rates than middle-aged drivers. Although drivers over 65 make up 11.2% of the driving population in the United States, they are involved in only 7% of all accidents. A study of Cerelli (1989) was cited reporting that drivers over 75 have a crash involvement rate that is 2.5 times lower than that of drivers aged 40, and 5 times lower than that of 20 year old drivers. According to Brouwer and Ponds (1994) the fatality risk for drivers of age 70 is about three times as high compared to drivers at age 20, due to physical changes such as osteoporosis and decreased cardiovascular efficiency resulting in an increased physical vulnerability. Correction for this increased vulnerability gives a better impression of actual accident involvement of older drivers compared to younger drivers. Application of this correction factor resulted in almost equal casualty risks for 35 and 70 year old drivers in the Netherlands in the eighties. Evans (1988) also found that when correcting for increased vulnerability, fatalities for older drivers are less than for male drivers under 20.
The results suggest that, although older drivers suffer from decreased performance on most tests of psycho-motor and attentional abilities, their accident risk is not dramatically different from drivers of other age groups. In situations with high time-pressure and situations beyond the control of the driver accident risk appears to increase for older drivers. A possible cause for this phenomenon may be found in the distinction between self-paced and forced-paced driving situations. When the driving task is self-paced, the situation allows the driver to compensate for performance deficits. However, compensation is impossible in forced-paced situations. In that case the driver is subjected to higher levels of time-pressure. The results may then be explained in terms of a process of adaptation: older drivers may compensate for their degradations of psycho-motor abilities by changing their behaviour both at the strategic level and the tactical level. There are a number of research findings in support of adaptive mechanisms.
The ultimate decision at the strategic level is to give up driving. Kosnik et al. (1990) found that older drivers who had recently given up driving reported more visual problems compared to older drivers who had not given up driving. The results suggested that older drivers are aware of their visual deficits and that this awareness influenced decisions about driving. At the strategic level decisions are also made regarding the time of driving. Planek and Fowler (1971) and Ysander and Herner (1976) found that older drivers avoided driving in the dark, on icy roads and in unknown cities more than younger drivers. According to these authors, self-selection seems to be a factor of great importance when judging the traffic safety risks of elderly drivers. Older drivers also may compensate for their age-related impairments by limiting their driving and avoiding risky situations and rush hours (Ranney and Pulling, 1990). In addition to this, there is some evidence in support of compensation at the tactical level. Ranney and Pulling found that older drivers drive slower compared to younger drivers. This was also reported by Rackoff and Mourant (1979). They cited the studies of Case et al. (1970) and Rackoff (1974) in which it was found that the vehicle speed of older drivers, in an instrumented vehicle, was about ten percent less than the speed of younger drivers. The tendency of older drivers to drive at lower speeds was also referred to by Rumar (1987). The proportion of accidents where speed is below average increases as a function of age. The number of studies on driver behaviour of elderly drivers in driving simulators is limited, because this age group is more susceptible to simulator sickness.
The following literature was referred to:
- Brouwer, W.H. (1989). Bejaarden in het verkeer. In: C.W.F. van Knippenberg, J.A. Rotherngatter and J.. Michon (eds.). Handboek sociale verkeerskunde. Van Gorcum, Assen/Maastricht, 331-349.
- Brouwer, W.H. and Ponds, R.W.H.M. (1994). Driver competence in older persons. Disability and Rehabilitation, 16, 149-161.
- Case, H.W.; Hulbert, S. and Beers, J. (1970). Driving ability as affected by age. Final Report No. 70-18. Institute of Transportation and Traffic Engineering. University of California, Los Angeles.
- Cerelli, E. (1989). Older drivers, the age factor in traffic safety. Report DOT-HS-807-402. U.S. Department of Transportation.
- Evans, L.E. (1988). Older driver involvement in fatal and severe traffic crashes. Journal of Gerontology, Social Sciences, 43, 186-193.
- Hakamies-Blomqvist, L. (1994). Compensation in older drivers as reflected in their fatal accidents.Accident Analysis & Prevention, 26, 107-112.
- Kosnik, W.D.; Sekuler, R. and Kline, D.W. (1990). Self-reported visual problems of older drivers. Human Factors, 32, 597-608.
- Planek, T.W. and Fowler, R.C. (1971). Traffic accident problems and exposure characteristics of the aging driver. Journal of Gerontology, 26, 224-230.
- Rackoff, N. (1974). An investigation of age related changes in driver’s visual search patterns and driving performance and the relation to tests of basic functional capacities. Ph.D. dissertation, The Ohio State University, Columbus, Ohio.
- Rackoff, N.J. and Mourant, R.R. (1979). Driving performance of the elderly. Accident Analysis & Prevention, 11, 247-253.
- Ranney, T.A. and Pulling, N.H. (1990). Performance differences on driving and laboratory tasks between drivers of different ages. Transportation Research Record 1281, 3-10.
- Rumar, K. (1987). Elderly drivers in Europe. In: Proceedings of roads and traffic safety on two continents, VTI report 331A, Linkoping, Sweden.
- Ysander, L. and Herner, B. (1976). The traffic behaviour of elderly male automobile drivers on Gothernburg, Sweden. Accident Analysis & Prevention, 8, 81-86.