Effects of Daylight Savings Time on Fatal Motor Vehicle Accidents

Background: Previous research has indicated that daylight savings time (DST) affects motor vehicle accidents, but the findings are rather controversial. Sleep loss or increased daylight has been found to be the main factor affecting changes in accident rates. The purpose of this research was to identify the effects of DST on motor vehicle accidents. Data and Methods: The Fatality Analysis Reporting System (FARS) data were collected for three weeks before and three weeks after the spring DST changes for eight consecutive years from 2003 to 2010. Paired t-tests were used to examine whether there were significant differences in traffic accidents before and after DST shift in two periods, 2003-2006 and 2007-2010. Beginning 2007, DST has been extended by four weeks. Results: Fatal traffic accidents were significantly increased after DST shifts in 2003-2006 (t=7.750, p<.01) but were not significantly different after DST shifts in 2007-2010 (t=.753, p>.05). This does not support earlier claim such as sleep loss and fatigue. An interesting pattern was emerged when accident rates were examined 4 weeks after DST shifts during 2007-2010 (similar to start time in earlier years). There was a significant increase in accidents between the first three weeks and the later three weeks after DST shits (t=2.258, p<.05). Conclusions: Contrary to earlier findings, DST shits in spring do not affect fatal accidents. Rather, psychological factors might play a role in the ,increase in fatal traffic accidents after the spring DST changes.