Life and Death at the CAFE: Predicting the Impact of Fuel Economy Standards on Vehicle Safety

Recent changes to the Corporate Average Fuel Economy (CAFE) standards in the United States mandate substantial improvement in automobile fuel economy over the next fifteen years. One of the ways that manufacturers improve fuel economy is to lower vehicle weights, which has impacts on safety. The innovation of this project is a novel maximum likelihood model that avoids issues of driver selection to separately identify the impact of vehicle weight on accident mortality. The key findings of the paper are: (1) A modest 5% average reduction in vehicle weight could increase annual accident fatalities by 4.9% or decrease them by 3.4% depending upon whether the reductions are concentrated at the lighter or heavier end of the current weight distribution; (2) Safety externalities attributiable to vehicle weight substantially exceed environmental ones; and (3) The relationship between vehicle weight and external safety e↵ects is such that a simple Pigovian excise tax on gasoline is unlikely to much improve e ciency.