The criminalization of impaired driving in Canada: Assessing the deterrent impact of Canada's first per se law

Objective: The goal of this article is to assess the effectiveness of Canada's first per se law criminalizing driving with a blood alcohol concentration of over 0.08%, the Breathalyser Law introduced in 1969, in reducing drinking-driver-related fatalities. We also examine the long-term deterrent effect of this law on driver fatality rates. In the analyses we include such potentially confounding influences on drinking-driver fatality rates as the founding of Mothers Against Drunk Driving (MADD), Canada; the introduction of Ontario's mandatory seatbelt law; per capita alcohol consumption; the unemployment rate; vehicles registered per capita; and precipitation rates. Method: Interrupted time series analysis with auto-regressive integrated moving average modeling was applied to the annual number of motor vehicle driver fatalities in Ontario for the period 1962-1996 to examine drinking- and nondrinking-driver fatalities. Results: A significant intervention effect was found for the Breathalyser Law in Ontario, which was associated with an estimated reduction of 18% in the number of fatally injured drinking drivers. No corresponding effect was observed for nondrinking-driver fatalities. Per capita alcohol consumption was positively associated with drinking-driver fatalities; Ontario's mandatory seatbelt law was linked to nondrinking-driver fatalities; and the formation of MADD, Canada, was strongly associated with drinking- and nondrinking-driver fatalities. Conclusions: These data provide evidence that Canada's per se law had a specific deterrent effect that resulted in a reduction in drinking-driver fatalities. A long-term deterrent effect was also observed, which is in contrast to the early policy literature on impaired driving.