A tale of two surveys – Explaining older drivers' low mileage bias

The widespread claim that older drivers are overly involved in crashes has apparent support from crash data, especially when rates are calculated on a per-kilometre basis. However, independent of age, drivers driving long distances will typically have lower crash rates per kilometre than those driving shorter distances. Data from a growing number of sources confirm that when the crash rates of drivers of different ages are compared after being matched for yearly driving distance, most older drivers are as safe or even safer than drivers from all other age groups. The present papers uses two travel surveys- one in Victoria, one in New Zealand – to demonstrate and quantify two factors which contribute to the association between older drivers? extent of annual mileage and level of crash involvement. The two factors are: (1) the extent to which low mileage older drivers are more likely to use the urban road network with its greater concentration of potential conflict points; and (2) the extent to which low mileage older drivers are more likely to have reduced fitness to drive.