In the segment Daylight Saving Time - How Is This Still A Thing? of John Oliver's Last Week Tonight it is said:

Studies say that there's an increase in car accidents and work related injuries the week after the time change.

Is an increased amount of accidents after the daylight time saving a fact that's well established by studies?

  • Christian, is there anything more we can add? – Sean Duggan Nov 8 '17 at 15:34
  • @SeanDuggan : If a single study finds X that doesn't mean that X is academic consensus because there might be nine other studies that found ¬X. – Christian Nov 8 '17 at 16:46

Here's one 2001 study that shows a small, but notable, increase:

Fatal accidents following changes in daylight savings time: the American experience

Conclusions: The sleep deprivation on the Monday following shift to DST in the spring results in a small increase in fatal accidents. The behavioral adaptation anticipating the longer day on Sunday of the shift from DST in the fall leads to an increased number of accidents suggesting an increase in late night (early Sunday morning) driving when traffic related fatalities are high possibly related to alcohol consumption and driving while sleepy. Public health educators should probably consider issuing warnings both about the effects of sleep loss in the spring shift and possible behaviors such as staying out later, particularly when consuming alcohol in the fall shift. Sleep clinicians should be aware that health consequences from forced changes in the circadian patterns resulting from DST come not only from physiological adjustments but also from behavioral responses to forced circadian changes.

This 2014 study from the University of Colorado, Boulder, shows that 10 years of data accrual shows a definite effect as well.

Spring Forward At Your Own Risk: Daylight Savings Time and Fatal Vehicle Crashes


Despite mounting evidence that Daylight Saving Time (DST) fails in its primary goal of saving energy, some form of DST is still practiced by over 1.5 billion people in over 60 countries. I demonstrate that DST imposes high social costs on Americans, specifically, an increase in fatal automobile crashes. DST alters fatal crash risk in two ways: disrupting sleep schedules and reallocating ambient light from the morning to the evening. First, I take advantage of the discrete nature of the transitions between Standard Time and DST to measure the impact of DST on fatal crashes in a regression discontinuity design. Then, to measure the duration of the effect, I exploit variation in the coverage of DST created primarily by a 2007 policy change, in a day-of-year fixed effects model. Both models reveal a short-run increase in fatal crashes following the spring transition and no aggregate impact in the fall. Employing three tests, I decompose the aggregate effect into ambient light and sleep mechanisms. I find that shifting ambient light reallocates fatalities within a day, while sleep deprivation caused by the spring transition increases risk. The increased risk persists for the first six days of DST, causing a total of 302 deaths at a social cost of $2.75 billion over the 10-year sample period, underscoring the huge costs of even minor disruptions to sleep schedules.

  • 1
    Do you believe it's the only study on the subject, otherwise is there a reason to look specifically at this study? – Christian May 31 '16 at 18:17
  • That was the first one that I found that looked reputable. Locating some other ones now. – Sean Duggan May 31 '16 at 18:18
  • I am sure there are probably other papers, but I don't have the time to do further research. – Sean Duggan May 31 '16 at 18:53

For Canada, according to Daylight Savings Time and Traffic Accidents N Engl J Med 1996; 334:924-925

The loss of one hour's sleep associated with the spring shift to daylight savings time increased the risk of accidents. The Monday immediately after the shift showed a relative risk of 1.086 (95 percent confidence interval, 1.029 to 1.145; ξ2 = 9.01, 1 df; P<0.01). As compared with the accident rate a week later, the relative risk for the Monday immediately after the shift was 1.070 (95 percent confidence interval, 1.015 to 1.129; ξ2 = 6.19, 1 df; P<0.05). Conversely, there was a reduction in the risk of traffic accidents after the fall shift from daylight savings time when an hour of sleep was gained. In the fall, the relative risk on the Monday of the change was 0.937 (95 percent confidence interval, 0.897 to 0.980; ξ2 = 8.07, 1 df; P<0.01) when compared with the preceding Monday and 0.896 (95 percent confidence interval, 0.858 to 0.937; ξ2 = 23.69; P<0.001) when compared with the Monday one week later. Thus, the spring shift to daylight savings time, and the concomitant loss of one hour of sleep, resulted in an average increase in traffic accidents of approximately 8 percent, whereas the fall shift resulted in a decrease in accidents of approximately the same magnitude immediately after the time shift.

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