Alcohol, drugs, and impairment in fatal traffic accidents in British Columbia.

Blood samples and accident records of 41 female and 186 male fatally injured drivers were examined. Analyses suggested that drugs other than alcohol are causally related to fatal traffic accidents in British Columbia. Toxicologies showed: 37% alcohol only, 11% alcohol and drugs, and 9% drugs only. The most frequently found drugs were: 48% alcohol, 13% tetrahydrocannabinol or its metabolites (THC/THCCOOH), 4% cocaine, and 5% diazepam. In addition, alcohol-only impairment was missed by investigating police officers in many cases, impairment by alcohol and drugs was mistakenly identified as alcohol-only impairment, and drug-only impairment was misclassified as "driving without due care and attention".