Effects of introducing an administrative .05% blood alcohol concentration limit on law enforcement patterns and alcohol-related collisions in Canada

•Canadian administrative .05% or .04% BAC laws were effective to reduce the percentage of fatally-injured drivers with BAC of all levels (from .05% to .15% and over).•The introduction of administrative laws was neither associated with changes in the rate of driving while impaired incidents reported under the Criminal Code nor in the probability of being charged for driving while impaired. Except for Quebec, all Canadian provinces have introduced administrative laws to lower the permitted blood alcohol concentration (BAC) to .05% or .04% for driving—or having the care of—a motor vehicle. Using linear mixed effects models for longitudinal data, this study evaluates the effect of administrative BAC laws on fatal alcohol related crashes and law enforcement patterns in Canada from 1987 to 2010. Results reveal a significant decrease of 3.7% (95% C.I.: 0.9–6.5%) in fatally injured drivers with a BAC level equal or greater than .05% following the introduction of these laws. Reductions were also observed for fatally injured drivers with BAC levels greater that .08% and .15%. The introduction of administrative BAC laws led neither to significant changes in the rate of driving while impaired (DWI) incidents reported by police officers nor in the probability of being charged for DWI under the Criminal Code.