Do Stricter Drink-Driving Limits Improve Road Safety? Evidence from Scotland’s BAC Reform

Abstract

This study evaluates the impact of Scotland’s 2014 reduction in the legal blood alcohol concentration limit from 0.08 to 0.05 g/dL on road traffic accidents. Using yearly data aggregated at the Middle-layer Super Output Area (MSOA) level for Engalnd and Wales and Intermediate Zone (IZ) level for Scotland, a balanced panel dataset of 7,940 spatial units across Great Britain from 2008 to 2019 is constructed. The analysis employs the Synthetic Difference-in-Differences (SDID) method to estimate a credible counterfactual. The results indicate a significant reduction in crash rates following the policy, with an estimated decline of 12.00% in total crashes. Stronger effects are observed during periods associated with higher alcohol-related risk, with reductions of 31.63% in night-time crashes and 25.28% in weekend crashes. Robustness checks, including placebo tests, confirm the statistical significance of these findings.