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When examining 19 states that had medical marijuana laws on the books by 2014, researchers found that their average rate of traffic deaths fell 11 percent after the laws were enacted. The happy side-effect wasn’t uniform, however; only seven states saw significant reductions, while two states saw increases. Nevertheless, the authors of the new report in the American Journal of Public Health argue that the data bucks the common criticism that more pot access should increase car crashes and injuries.

Drops in traffic deaths may, in part, be explained by people swapping alcohol for pot, leading to reduced drunk driving, the study’s authors speculated. To back that up, the authors note that the lives spared tended to belong to younger people, particularly 25- to 44-year-olds—an age group frequently involved in alcohol-related traffic deaths.