Survey of older licence holders: Are they still driving? What is the association between mileage driven and crash risk?

Older drivers have higher per-distance crash rates than most other driver age groups. This has been used to justify a range of road safety countermeasures, including licensing policies requiring demonstration of fitness to drive. In Victoria, where there is no age-based mandatory re-testing, older drivers have less crash involvement on a per licence basis than older drivers in other States. As they are issued with 10 year licences, in 2004 VicRoads commissioned a survey of 2,000 drivers aged 65 years or older to determine how many were still driving. Another primary purpose of the survey was to assess whether older drivers? apparent high crash risk was spread fairly evenly across all drivers in this age group. As part of this task, a number of different ways of calculating crash involvement were explored. Analyses of the survey data showed that older drivers did not comprise a homogeneous group in relation to crash risk. The lower the mileages driven, the higher the crash risk, such that older drivers travelling 20 km or less per week had around ten times the per-distance crash rate of drivers travelling 200 km or more per week. This paper describes the association between mileage driven and crash risk, and discusses the implications for the development of road safety countermeasures.