Drug and alcohol involvement in four types of fatal crashes.

OBJECTIVE The aim of this study was to explore the relationship of drunk and drugged driving to the occurrence of fatal crashes associated with speeding, failure to obey/yield, inattention, and seat belt nonuse. METHOD We examined data for fatally injured drivers involved in single-vehicle crashes killed in states in which more than 79% of the drivers were tested for drugs other than alcohol and had a known result. RESULTS About 25% of the drivers tested positive for drugs, a figure almost double that estimated by the 2007 National Roadside Survey. Cannabinoids and stimulants each contributed to about 23% of the drugpositive results (6% among all fatally injured single-vehicle drivers). Stimulants more than cannabinoids were found to be associated with the four types of crashes under study. Some drugs showed a protective effect over the four crash types under study. Significant interactions between drugs and alcohol were observed. Stimulants contributed to the different types of fatal crashes irrespective of the levels of alcohol consumed by the drivers. CONCLUSIONS This study provides further evidence of a link between drug consumption and fatal crashes. It also opens the door to some interesting and sometimes unexpected questions regarding the way drugs contribute to crashes, which we found varies depending on the type of crash considered, the class of drug, and the presence of alcohol. Research is also needed on drugs that could have a protective effect on the occurrence of fatal crashes. These findings could be highly relevant to the design of drug-related traffic laws and programs targeted at curbing drugged driving.