Abstract
Drink and drug driving can have an impact on the driving performance and accident risk. This epidemiological study, which forms part of the European project IMMORTAL, investigates the prevalence of eight defined drug groups, including alcohol, among drivers in the Tilburg police district. To examine the relative accident risk, the accident rate of users of one or more of these substances was related to the accident rate of drivers not using one of these substances. In addition an observational method of detecting drug impaired drivers was tested.