Highlights • The effectiveness of Korea’s new stricter drunk-driving laws was assessed. • The laws reduced alcohol-related road traffic injury, minor injury, and crash rates. • The laws had no impact on alcohol-related road traffic death and severe injury rates. • Additional strategies are needed to reduce alcohol-related road traffic outcomes.

Abstract In December 2018, new drunk-driving laws were enacted in Korea to impose stricter penalties and standards for driving under the influence of alcohol. This study aimed to estimate the effects of stricter drunk-driving laws on alcohol-related road traffic death, injury, and crash rates in Korea. Using police-reported traffic accident data and registered vehicle data from 2013 to 2020, monthly road traffic outcome rates were calculated: the response series involved alcohol-related rates and the non-equivalent control series involved total and non-alcohol-related rates. Based on a controlled interrupted time-series design using Bayesian structural time-series models, effects of the laws on alcohol-related road traffic outcome rates were evaluated. After implementation of these laws, the alcohol-related road traffic crash rate decreased by 14.3% (95% credible interval [CrI] −26.8% to −1.9%), alcohol-related road traffic injury rate by 17.6% (95% CrI −31.6% to −3.8%), and alcohol-related minor road traffic injury rate by 20.2% (95% CrI –32.4% to −7.7%). Alcohol-related road traffic death and severe injury rates also decreased more than the declining trends in the pre-period, but reduced non-significantly by 15.0% (95% CrI −47.2% to 17.3%) and 9.9% (95% CrI –33.9% to 14.5%), respectively. The mixed effectiveness of Korea’s new drunk-driving laws on alcohol-related road traffic outcomes suggests that additional strategies are necessary to consistently and effectively reduce alcohol-related road traffic outcomes. More research is needed on ways to enhance the effectiveness of drunk-driving laws.