Quick Take: An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment

Individuals that drive while under the influence of alcohol are at an increased risk of being involved in traffic accidents, contributing to the morbidity and mortality of the individual and others. In this observational natural experiment in Scotland, the effects of lowering the legal driving limit from a blood alcohol content (BAC) of 0.08 grams per deciliter to 0.05 grams per deciliter were examined. Specifically, investigators evaluated the impact of this legislation on alcohol consumption and traffic accidents, using those in England and Wales, where laws did not change, as a control group. Using market research of on-trade (bars and restaurants) and off-trade alcohol consumption (grocery and convenience stores), as well as police reports and automated traffic counters, both alcohol consumption and traffic accident rates were estimated. Researchers found no significant difference in accident rates in Scotland before and after the change in legal limit (RR 1.01, 95% CI 0.94 to 1.08, p=0.77). Compared to England and Wales, the rate of accidents in Scotland was significantly higher after the lowering of the BAC limit (RR 1.07, 95% CI 1.02 to 1.13, p=0.007).  Additionally, there was no significant change in per-capita off-trade sales (-0.3%, 95% CI -1.7 to 1.1, p=0.71). However, there was a significant decrease in per-capita on-trade sales estimates (-0.7%, 95% CI -0.8 to -0.5%, p<0.0001). Investigators concluded that lowering the legal driving limit for BAC did not lead to a reduction in traffic accidents, but did lead to a slight reduction in consumption of alcohol in bars and restaurants.

Click to read the study in Lancet

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