The effects of Daylight Saving Time (DST) on vehicle crashes in Minnesota

  • Published: Journal of Safety Research Volume 41, pp. 513–520, 2010
  • Authors: A. Huang and D. Levison
  • Date Added: 18 Mar 2013
  • Last Update: 18 Mar 2013
  • Format: pdf


To assess the effects of putting clocks forward in Spring.


Based on vehicle RTI data in Minnesota from 2001 to 2007, this paper evaluates long- and short-term effects of DST on daily vehicle RTIs. To provide evidence to explain the causes of more/fewer RTIs in DST, the impact of DST was examined on RTIs in four periods of a day: 3am-9 am, 9am-3pm, 3pm-9 pm and 9 pm-midnight. The effects of risk and exposure to traffic are also separated.

Key Findings:

  • The relationship between DST and road injuries or fatalities has been a topic of extensive research.

  • There are generally two schools in studying the effects of DST on road safety, which concentrate on either long-term effects or short-term effects.

  • One of the schools claims that DST in the long run decreases vehicle RTIs due to better visibility in the evenings, reducing the likelihood of RTIs in darkness.

  • The other school contended that time change to DST resulted in more vehicle RTIs in the short run.

  • The main hypothesis was that time change in spring deprived people of one-hour of sleep, which, in the short run, could induce drivers’ sleepiness or fatigue while driving.

  • Some clinical research performed controlled experiments to examine the relationship between hours of sleep and drivers’ response time and vigilance; their main conclusion was that one-hour less sleep can boost the rise of traffic RTIs.

  • In addition, some other studies found that time change to DST was associated with an increase in fatal vehicle RTIs, and attributed it to possible drivers’ alcohol-drinking or late-night driving behaviour because an extra hour is available in the evening.

  • In contrast, other research found that time change did not have a statistically significant impact on vehicle RTIs.

  • While different data may produce different results, the effects of DST do not seem to have been sufficiently investigated.

  • The major finding of the data analysis is that the short-term effect of DST on RTIs on the morning of the first DST is not statistically significant.

  • Moreover, it is interesting to notice that while DST per se is associated with fewer RTIs during dusk, this is in part offset because it is also associated with more traffic on roads (and hence more RTIs).

  • A path analysis shows that overall DST reduces RTIs.

  • Daylight saving time can lead to fewer RTIs on roads by providing better visibility for drivers.


Daylight Saving Time, Road Traffic Incidents, Exposure, Traffic volume


Reviews previous literature and presents data analysis on the short-term effects of putting the clocks back by one hour in Autumn.