Toxicological investigations of drivers killed in road traffic accidents in Norway during 2006-2008

Abstract

Aim: To study the results from the toxicological investigations of drivers of cars and vans who were fatally injured in road traffic accidents in 2006-2008 and discuss the findings in relation to the proposed legal limits and impairment thresholds for drugs.

Methods: Analyses for alcohol, illegal drugs and psychoactive medicinal drugs were performed by the Norwegian Institute of Public Health. Information on type of accident (single or multiple vehicles) and type of road (urban or rural) was obtained from Statistics Norway.

Results: Toxicological analyses were requested for 59% of the fatally injured drivers. Drivers involved in single vehicle accidents were more often subject to toxicological investigations, so were also young male drivers and drivers killed on urban roads. Alcohol or drugs were found in concentrations above the current (for alcohol) or proposed (for drugs) legal limits in samples from 37.8% of the drivers; from 64.3% those killed in single-vehicle accidents and 17.9% of those killed in multiple-vehicle accidents. In total, alcohol was found in 25.0%, illicit drugs in 10.2%, and psychoactive medicinal drugs in 13.8% of the samples. Combinations of alcohol and drugs were found in 5.1% and multiple drugs without alcohol in 6.1% of the samples. The prevalence of alcohol or drugs was higher in samples from males than females, higher in samples from young drivers, and higher in samples from drivers killed during weekends. Two thirds of the drivers with alcohol or drug concentrations above the current or proposed legal limits had concentrations above the proposed high impairment threshold. About 60% of the latter ones were impaired by alcohol only, 20% by drugs in combination with alcohol, and 20% by drugs only, mainly due to multi-drug use.

Conclusion: The use of alcohol or drugs before driving was a significant contributing factor in fatal road traffic accidents, particularly in single vehicle accidents, and particularly among young male drivers. Alcohol was the most significant intoxicant, but multi-substance use was also significantly prevalent. The majority of the drivers with alcohol or drug findings were strongly impaired.