DRUGS AND ACCIDENT RISK IN FATALLY-INJURED DRIVERS

Risk analysis studies to investigate the contribution of drugs to accident causation are limited. The study investigated 1052 fatally injured drivers. Drugs (including alcohol) were detected in 49 percent of drivers. Alcohol was detected in 36 percent, whilst other drugs were detected in 22 percent. 13 percent had only drugs detected. The remaining 9 percent of the population involved a combination of drugs and alcohol. Drivers in whom only opiates were detected gave an odds ratio of 2.4, marijuana 0.6., stimulants 1.4 and benzodiazepines 1.0. By contrast the odds ratio for alcohol was 6.8. Drivers with higher than therapeutic concentrations detected represented 2.1 percent. Most of these drivers were found to be culpable. Multiple drug cases also tended to be culpable. The culpability rate in this group was 89 percent compared to 70 percent in drug-free drivers. These data show that only a small proportion of impaired drivers are drug effected, the remainder being impaired by alcohol. The relative risk for psychoactive drugs is also not uniform, with marijuana use providing the least effect on risk, whilst opiate use seems to provide the largest increase in risk compared to the other drug groups studied. (a) For the record of the covering entry of this conference, please see IRRD abstract no 868581.