In the presence of labor market failures, workers may have financial incentives that penalize safety. We study this question in the context of trucking, an industry that ships over two thirds of all freight in the United States, and a setting in which workplace accidents often generate a public safety externality. Using data on 1.4 million truck crashes across the continental United States, we first show that icy weather poses a uniquely strong occupational hazard to truckers: a wet day between -5°C and 0°C increases crashes by 153 percent, an effect that is over twice as large as that for all-vehicle accidents. We then evaluate a policy introduced to curb excessive driving, but one that inadvertently heightened truckers’ incentives to engage in other unsafe driving practices, such as speeding. The policy increased the ice-crash relationship by 28 percentage points, highlighting the importance of considering workers’ incentives when designing labor market interventions that aim to promote safety.