The biannual changing of the clocks is once again looming in the United States, with Daylight Saving Time ending on Sunday, November 6. Research out this week may throw fuel onto the long-running debate over whether to end the practice and how exactly it should be done. By analyzing millions of hours of traffic data, the study estimates that establishing permanent Daylight Saving Time would prevent more than 35,000 deer deaths and thousands of human injuries from animal-car collisions every year.
Daylight Saving Time, for those unclear with the concept, mandates that people set their clocks one hour forward during the warmer months of the year; in the U.S., this is from March to November. Once the colder months show up, the clocks are set back an hour to Standard Time. The back-and-forth is meant to ensure that people on average get more daylight during their most active hours, with the return to Standard Time in the fall meaning that sunrises and sunsets begin earlier as well, relative to DST (DST was not enacted on behalf of farmers, as is commonly believed).
Unfortunately, evidence has been piling up over the years that these clock changes are actively harmful. Studies have found, for instance, that fatal car crashes increase in the week following the return of DST, at least in part because the abrupt change in sleep patterns can induce a sort of jetlag in drivers. As a result, some experts and even lawmakers have launched concerted efforts to abolish the shifts and to establish a permanent year-long routine.
Study author Calum Cunningham, a wildlife researcher at the University of Washington, and his colleagues had been studying the potential effects on sunlight on animal-vehicle collisions when they noticed that the implementation of DST and Standard Time every year meant that sunrises and sunsets occur at different clock hours. To better understand the impact that these shifts could have on accidents, they decided to look closer at data collected by the U.S. Department of Transportation. Ultimately, Cunningham and his team analyzed over a million deer-related car crashes and nearly 100 million hours worth of traffic data. And they came to a pretty clear conclusion.
“The twice-yearly shifts between time systems cause an abrupt change in the timing of human activity relative to sunrise and sunset. This means that shifting from daylight saving to standard time in the autumn causes peak traffic to shift to after sunset,” Cunningham told Gizmodo in an email. “Because animals are more difficult to see at night, the increase in traffic after dark causes a 16% increase in deer-vehicle collisions [in the week after Standard Time returns].”
Going a step further, the team also created models for how the frequency of these crashes would be affected by either permanent Daylight Saving Time or Standard Time. They estimate that permanent DST would prevent about 36,550 deer deaths, 33 human deaths, 2,054 human injuries, and $1.19 billion in accident costs per year, with the largest benefits seen in the eastern portions of time zones. By contrast, permanent Standard Time would lead to an extra 73,660 deer deaths, 66 human deaths, 4,140 injuries, and $2.39 billion in costs every year. These estimates, Cunningham added, are likely to be conservative, since the model relies on reported collision data and many such crashes aren’t officially tallied. The team’s findings were published Wednesday in Current Biology.
While many people would prefer sticking to a consistent clock schedule, there’s no shortage of debate over which system is best to keep. Earlier this year, for instance, the U.S. Senate surprisingly passed a bill that would enshrine permanent DST. But the decision was soon met by fierce criticism from medical experts and organizations. These groups have long argued that permanent Standard Time would be better because of DST’s well-established, if subtle, negative effects on our health, particularly our sleep patterns.
Cunningham says that their findings add some weight to the argument that permanent DST would be best to adopt, though he notes that either change would come with trade-offs. Indeed, in an accompanying editorial, sleep scientist and chronobiologist Eva Winnebeck argues that the reduction in human deaths from animal-related crashes as a result of permanent DST likely wouldn’t offset the increase in human deaths from car accidents in general caused by DST-induced drowsiness (perhaps over 1,200 a year, based on research she cites on the effects of living in misaligned time zones).
The Senate bill is languishing in Congress, with no apparent plans by the House to vote on their own version anytime soon. So for at least one more year, DST will come to its scheduled end this month. But even if DST is ultimately abolished in place of permanent Standard Time, there may yet be a way to better ensure the safety of both deer and humans. Cunningham notes that animal-related collisions seem to be 14 times more likely in the two hours after sunset than in the two hours before it. So any policies that can reduce nighttime driving overall should still be able to prevent many accidents, even in the absence of permanent DST. These policies could also be focused on hotspots of deer activity and timed to November specifically, since that’s when deer are more active for the two to three weeks of their breeding season. And it also means that people can do their own part to keep themselves and their furry neighbors safe on the road.
“In terms of what individual people can do, if you are able to get your driving done before nightfall, then that will significantly reduce your risk of killing wildlife and in turn reduce the risk of harming yourself,” Cunningham said.