Spring forward at your own risk: Daylight saving time and fatal vehicle crashes

Abstract

Daylight Saving Time (DST ) impacts over 1.5 billion people, yet many of its impacts on practicing populations remain uncertain. Exploiting the discrete nature of DST transitions and a 2007 policy change, I estimate the impact of DST on fatal automobile crashes. My results imply that from 2002-2011 the transition into DST caused over 30 deaths at a social cost of $275 million annually. Employing four tests to decompose the aggregate effect into an ambient light or sleep mechanism, I find that shifting ambient light only reallocates fatalities within a day, while sleep deprivation caused by the spring transition increases risk.