Are There Really More Accidents Around Daylight Saving Time Changes?

man yawning in car
Daylight savings time has become a fact of life over the decades, but does it continue to throw off our sleep schedule? Stockbyte/Thinkstock

There are a lot of things to dislike about daylight saving time: the disruption in our sleep schedule, the onslaught of seasonal puns in retail advertisements, the fact that it doesn't work as well at saving energy as we've always been told, and thus, it really serves no purpose.

But have you ever thought about the possibility that daylight saving time (DST) might actually be dangerous? When the clocks spring forward and fall back each year, it's only by an hour, but research suggests it may take days to adjust to the time difference. And during that adjustment period, there is a spike in car crashes, especially after we "spring forward" and lose an hour of sleep.


Researchers at the University of Colorado at Boulder studied the daylight saving time period (from March to November 2002-2011) and found over 30 deaths annually (or 302 over the 10-year period) could have been caused by the DST change. And the U.S. government's Fatality Analysis Reporting System found a 17 percent increase in traffic incident-related deaths the Monday after the spring time change. Traffic fatalities all that week were also higher than average. Some of the effects can be attributed to lower visibility (the fact that it's earlier, and therefore darker, than drivers are accustomed to), but most of the accidents, experts say, were because people are struggling to stay awake behind the wheel. Some police departments say that there's about a 10 percent increase in crashes just after the time change [source: Boynton].

In 2020, a study published in Cell Biology looking at motor vehicle fatality data from the Fatality Analysis Reporting System (1996-2017) found that there was a 6 percent increase in motor vehicle fatalities the week DST started, which translated to about 28 deaths per year, most of which occurred in the mornings. This fatality rate decreased the week after DST started and there was no subsequent increase in traffic deaths when the clocks reverted to Standard Time in the fall.

The traffic statistics alone seem like pretty conclusive evidence that daylight saving time is more than a mere inconvenience. And researchers say that the grogginess we feel for the first couple of days after we change the clocks might just be scratching the surface of how our bodies actually process the disruption. People who only sleep four or five hours a night under normal circumstances are at a much higher risk of causing a car crash than people who sleep six or seven hours a night, and people who get eight hours of sleep or more are least likely to cause a crash. But when sleep cycles get disrupted, everyone gets messed up. Perhaps it's time to abolish DST?


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Related Articles

  • Boynton, Donna. "Deadly car crashes spike after changing clocks for Daylight Saving Time." Worcester Telegram. March 7, 2015. (May 5, 2015)
  • Fritz, Joseph, et al. "A Chronobiological Evaluation of the Acute Effects of Daylight Saving Time on Traffic Accident Risk." Current Biology. Feb. 24, 2020 (March 5, 2020)
  • Worland, Justin. "How Daylight Saving Time Can Be Dangerous." Time. Oct. 31, 2014. (May 5, 2015)