An evaluation of immediate roadside prohibitions for drinking drivers in British Columbia: findings from roadside surveys.

Objective: The purpose was to determine the impact of new immediate roadside prohibitions (IRPs) for drinking drivers introduced in British Columbia in September 2010 as assessed by random roadside surveys of alcohol and drug use among nighttime drivers.

Methods: Two roadside surveys were conducted prior to and following the introduction of IRPs. Drivers were randomly selected from the traffic stream in 5 cities 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 3:00 a.m. on Wednesday through Saturday nights in June 2010 and again in June 2012.

Results: Driving after drinking decreased significantly following the introduction of IRPs. In particular, the percentage of drivers with blood alcohol concentrations (BACs) over 80 mg/dL decreased by 59 percent; drivers with BACs of at least 50 mg/dL decreased by 44 percent. The decreases in drinking and driving were not restricted to specific subgroups of drivers but were universal across age groups, sex, and communities. The results also revealed a changing pattern of drinking of driving. For example, the typical pattern of increased drinking and driving on weekend nights was not observed and the prevalence of drinking drivers on the road during late night hours was less than half that found in 2010. The prevalence of drug use by drivers in 2012 did not change from the levels reported in 2010.

Conclusions: The IRP program combined immediate short-term roadside suspensions with vehicle impoundment and monetary penalties to enhance the swiftness, certainty, and perceived severity of sanctions for drinking and driving. The introduction of these measures was associated with a substantial reduction in the prevalence of driving with a BAC over 50 mg/dL and driving with a BAC over 80 mg/dL.