"Studies of hospitalised, seriously injured car drivers were conducted in six countries, and studies of car drivers killed in accidents took place in four countries. Among the injured or killed drivers, the most commonly consumed substance was alcohol alone, followed by alcohol combined with another substance. The use of illicit drugs alone was not frequently detected. After alcohol, the most frequently found substance among injured drivers was tetrahydrocannabinol (THC) followed by benzodiazepines, whereas, among drivers killed in accidents, it was benzodiazepines."


European Monitoring Centre for Drugs and Drug Addiction, "Driving Under the Influence of Drugs, Alcohol and Medicines in Europe — findings from the DRUID project" (Luxembourg: Publications Office of the European Union, 2012), doi: 10.2810/74023, p. 6.