Permanent daylight saving time would save more than 30,000 deer killed by cars per year: study

Making daylight saving time permanent would save the lives of more than two dozen people annually and result in about 30,000 fewer deer being killed in car collisions, according to a new study.

Researchers at the University of Washington estimated that keeping daylight saving time year-round would prevent 36,550 deer deaths, 33 human deaths, over 2,000 human injuries and nearly $1.2 billion in costs annually.

A big part of those reductions would be seen each fall during the switch from daylight savings to standard time.

The study’s authors said that nearly 10% of annual deer-vehicle collisions occur in the two-week period around the November time change, and there’s a 16% increase in collisions between drivers and deer in the first week after the time change. 

Deer are also about 50% more active during this time because they’re in the middle of their mating season. 

“We believe that this fall spike really happens due to the overlap of these two factors: the breeding season and the change from daylight saving time back to standard time,” Laura Prugh, an associate professor of wildlife sciences at UW and one of the study’s authors, said in a press release. “We don’t see a corresponding shift in deer-vehicle collisions in the spring during the other time change, and we believe that’s in part because spring is not a breeding season for deer.” 

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Deer are naturally the most active around sunrise and sunset. Researchers said that collisions between deer and drivers were 14 times more frequent in the two hours after sunset than the two hours before sunrise. 

Researchers looked at more than 1 million deer-vehicle collisions from 1994 to 2021. The study’s authors said that roughly 2.1 million deer-vehicle collisions take place each year, killing about 440 people and injuring about 59,000. 

Under permanent standard time, the study estimates, there would be an increase of over 73,000 deer-vehicle collisions, 66 additional human deaths and over 4,100 more injuries. Permanent daylight saving time showed the opposite, according to the researchers’ estimates, with there being 2.3% fewer deer-vehicle collisions over the course of the year. 

The peer-reviewed study is titled “Permanent daylight saving time would reduce deer-vehicle collisions,” and was published in the journal Current Biology on Wednesday.