The unexpected effects of daylight-saving time: Traffic accidents in Mexican municipalities

Approximately 70 countries worldwide implement a daylight-saving time (DST) policy: setting their clocks forward in the spring and back in the fall. The main purpose of this practice is to save on electricity. However, by artificially changing the distribution of daylight, this practice can have unforeseen effects. This document provides an analysis of the impact of DST on traffic accidents in Mexico, using two empirical strategies: regression discontinuity design (RDD) and difference-in-differences (DD). The main finding is that setting the clocks forward an hour significantly lowers the total number of traffic accidents in the country’s metropolitan areas. However, there is no clear effect on the number of fatal traffic accidents.