Springing Forward Brings a Surge of Car Crashes

With the shift to Daylight Saving Time just a bit more than a month away, a new study is out that shows the rate of fatal car accidents in the United States spikes by 6% during the workweek following the “spring forward,” resulting in about 28 additional deaths each year.

The study from the University of Colorado Boulder also found that the farther west a person lives in his or her time zone, the higher their risk of a deadly crash that week.

“Our study provides additional, rigorous evidence that the switch to daylight saving time in spring leads to negative health and safety impacts,” said senior author Celine Vetter, assistant professor of integrative physiology. “These effects on fatal traffic accidents are real, and these deaths can be prevented.”

The findings come at a time when numerous states, including Oregon, Washington, California and Florida, are considering doing away with the switch entirely, and mounting research is showing spikes in heart attacks, strokes, workplace injuries and other problems in the days following the time change.

For the study – the largest and most detailed to date to assess the relationship between the time change and fatal motor vehicle accidents – the researchers analyzed 732,835 accidents recorded through the U.S. Fatality Analysis Reporting System from 1996 to 2017. They excluded Arizona and Indiana, where Daylight Savings Time was not consistently observed.

After controlling for factors like year, season and day of the week, they found a consistent rise in fatal accidents in the week following the spring time change. Notably, that spike moved in 2007, when the Energy Policy Act extended daylight saving time to begin on the second Sunday of March instead of the first Sunday in April.

“Prior to 2007, we saw the risk increase in April, and when daylight saving time moved to March, so did the risk increase,” said Vetter. “That gave us even more confidence that the risk increase we observe is indeed attributable to the daylight saving time switch, and not something else.”

With the arrival March 9 of daylight saving time, clocks shift forward by one hour, and many people will miss out on sleep and drive to work in darkness – both factors that can contribute to crashes.

Those on the western edge of their time zone, in places like Amarillo, Texas, and St. George, Utah, already get less sleep on average than their counterparts in the east – about 19 minutes less per day, research shows – because the sun rises and sets later but they still have to be at work when everyone else does.

“They already tend to be more misaligned and sleep-deprived, and when you transition to daylight saving time it makes things worse,” said first author Josef Fritz, a postdoctoral researcher in the Department of Integrative Physiology. In such western regions, the spike in fatal accidents was more than 8%, the study found.

The increase kicks in right away, on the Sunday when the clocks spring forward, and the bulk of the additional fatal accidents that week occur in the morning.

Changes in accident patterns also occur after the “fall back” time change, the study showed, with a decline in morning accidents and a spike in the evening, when darkness comes sooner.

Because they balance each other out, there is no overall change in accidents during the “fall back” week.