A statistical method for identifying areas of high crash risk to older drivers: final report

Effective use of finite roadway improvement budgets to accommodate an increasing number of older drivers requires that we be able to identify those locations where older drivers appear to have a heightened accident risk. Ideally, the accident records from a location (such as a particular intersection) should provide the information needed to assess the risk experienced there by a given group of drivers, but the lack of location and age-specific measures of exposure coupled with the relatively small accident samples available for particular locations makes the standard methods of high-hazard identification inapplicable. In this paper it is first shown how, by using an induced exposure approach, it is possible to test for the equality of group-specific accident rates at a given site by testing for the equality of two binomial probabilities which arise from a particular type of contingency table.