A roadside survey of alcohol and drug use among drivers in British Columbia.

Objective: The purpose was to determine the prevalence of alcohol and drug use among a random sample of nighttime drivers.

Methods: Drivers were randomly selected from the traffic stream in three cities in British Columbia and asked to provide a breath sample to determine alcohol content and a sample of oral fluid to be tested for the presence of psychoactive drugs. The survey was conducted between the hours of 9:00 p.m. and 03:00 a.m. on Wednesday through Saturday nights in June 2008.

Results: Of the 1533 vehicles selected, 89 percent of drivers provided a breath sample and 78 percent provided a sample of oral fluid. Key findings include: 10.4 percent of drivers tested positive for drug use. 8.1 percent of drivers had been drinking. 15.5 percent of drivers tested positive for alcohol, drugs, or both. Cannabis and cocaine were the drugs most frequently detected in drivers. Alcohol use among drivers was most common on weekends and during late-night hours; drug use was more evenly distributed across all survey nights and times. Alcohol use was most common among drivers aged 19 to 24 and 25 to 34; drug use was more evenly distributed across all age groups. Though driving after drinking has decreased substantially since previous surveys, the number of drivers with elevated alcohol levels (over 80 mg/dL) was higher than in the past.

Conclusions: The finding that drug use is more common than alcohol use among drivers highlights the need for a unique and separate societal response to the use of drugs by drivers commensurate with the extent of safety risks posed to road users. The observed differences between driving after drug use and driving after drinking have implications for enforcement and prevention.