Does decriminalizing hard drugs affect the risk of car accidents? The answer is hard to predict because the consequences of such a policy can run in different directions. To the extent that hard drugs impair coordination, judgment, and reaction time, legalization may increase accidents by making the drugs more easily available. But decriminalization might reduce accidents if people replace alcohol with substances that make them less likely to drive dangerously or drive at all. The net effect is an open question. This paper aims to answer it by looking at Oregon’s Measure 110 as a natural experiment, using a synthetic difference-in-differences (DID) approach to compare accident trends before and after its implementation. The findings suggest that decriminalization had no detectable effect on the rate of car accidents.