Risk of driving when positive for psychoactive substances

Background Driving with alcohol imposes an increased risk of injury, but the knowledge about other drugs is limited. Aims This paper aims to assess the risk of driving with alcohol, illicit drugs and medicines in various European countries. Method The risk of getting seriously injured or killed in an accident for a driver positive for a given substance was calculated with a case-control design as the odds ratio (OR) using logistic regression.

For risk of serious injury, cases consisted of samples from 2,490 drivers admitted to hospitals in six countries and controls of 15,832 non-injured drivers from roadside surveys in the same countries. For fatality risk, cases consisted of 1,112 killed drivers in four countries and controls of 21,917 non-injured drivers from roadside surveys in the same countries.

The risk estimates for serious injury and fatality for each substance were adjusted for age, gender and country. Results The results were based on risk estimates and their confidence intervals. The highest risk of getting seriously injured or killed was associated with BAC above 1.2 g/L and alcohol combined with other substances (OR between 20 and 750).

Other high risk groups weredrivers with BAC between 0.8 g/L and 1.2 g/L, multiple drugs and amphetamines (OR between 5 and 30). Medium increased risk was found for BAC between 0.5 and 0.8 g/L, cocaine, benzoylecgonine, illicit opiates and medicinal opioids (OR between 2 and 10). Slightly elevated risk was associated with cannabis and BAC between 0.1 g/L and 0.5 g/L (OR between 1 and 3).

Discussion and conclusion Risk of serious injury or fatality for drivers positive for the various substances was significantly above 1. However, high alcohol concentrations and the combination of alcohol and other drugs showed the highest risk and alcohol is therefore still the main problem in traffic compared to other psychoactive substances.