Title: Evaluating the impact of minimum unit pricing for alcohol on road traffic accidents in Scotland: a controlled interrupted time series study

Background On 1st May 2018, Scotland implemented Minimum Unit Pricing (MUP) of 0.50 GBP per unit of alcohol to lower alcohol consumption and related harms, and reduce health inequalities. We assessed the impact of MUP on road traffic accidents (RTAs) after 20 months of implementation. Methods A controlled interrupted time series design was used to evaluate the impact of MUP on RTAs (total, fatal, night-time) in Scotland and any effect modification across socio-economic deprivation groups. RTAs in England and Wales (E&W) were used as a control group. Covariates of severe weather events, bank holidays, seasonal and underlying trends were included. Results In Scotland, MUP implementation was associated with a 7.2% (95% CI: 0.9%,13.7% P=0.03) increase in the total number of RTAs. For the corresponding period in E&W, there was a 0.9% increase (95% CI: -2.3%,3.2% P=0.75). It is implausible that MUP caused this increase in RTAs, with the most likely explanation of these results being that unmeasured time-varying confounding affected Scotland and E&W differently. There was no evidence of differential impacts of MUP by level of socio-economic deprivation. Conclusion The introduction of MUP in Scotland was not associated with a lower level of RTAs.