Article Text


Impact of daylight saving time on road traffic collision risk: a systematic review
  1. Rachel N Carey1,
  2. Kiran M Sarma2
  1. 1 Department of Clinical, Educational and Health Psychology, University College London, London, UK
  2. 2 School of Psychology, National University of Ireland Galway, Galway, Republic of Ireland
  1. Correspondence to Dr Kiran M Sarma; kiran.sarma{at}


Background Bills have been put forward in the UK and Republic of Ireland proposing a move to Central European Time (CET). Proponents argue that such a change will have benefits for road safety, with daylight being shifted from the morning, when collision risk is lower, to the evening, when risk is higher. Studies examining the impact of daylight saving time (DST) on road traffic collision risk can help inform the debate on the potential road safety benefits of a move to CET. The objective of this systematic review was to examine the impact of DST on collision risk.

Methods Major electronic databases were searched, with no restrictions as to date of publication (the last search was performed in January 2017). Access to unpublished reports was requested through an international expert group. Studies that provided a quantitative analysis of the effect of DST on road safety-related outcomes were included. The primary outcomes of interest were road traffic collisions, injuries and fatalities.

Findings Twenty-four studies met the inclusion criteria. Seventeen examined the short-term impact of transitions around DST and 12 examined long-term effects. Findings from the short-term studies were inconsistent. The long-term findings suggested a positive effect of DST. However, this cannot be attributed solely to DST, as a range of road collision risk factors vary over time.

Interpretation The evidence from this review cannot support or refute the assertion that a permanent shift in light from morning to evening will have a road safety benefit.

  • systematic review
  • road safety
  • daylight saving time
  • collision risk.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

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  • Contributors KS conceived the systematic review and supervised the research. RC was primarily responsible for database searching and reviewing texts for inclusion. KS and RC both contributed to the data extraction, data analysis and manuscript drafting.

  • Disclaimer This paper is based on a report commissioned by the Road Safety Authority of Ireland. The views reported here are those of the authors and do not necessarily represent the views of the Road Safety Authority.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement The datasets supporting the conclusions of this article are available on request from the corresponding author.

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