Putting back the clocks in November is linked to a spike in car collisions with deer in the US
Collisions with deer in the US rise by 16 per cent in the week following the autumn clock change
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Moving to daylight saving time permanently could prevent 36,550 deer deaths, 33 human deaths and $1.19 billion in costs annually in the US.
Calum Cunningham at the University of Washington in Seattle and his colleagues have analysed data from 23 US states that included details on more than a million collisions between deer and vehicles from 1994 to 2021. There are an estimated 2.1 million of these accidents in the US every year, killing about 440 people and causing upwards of $10 billion in damage.
The team found that the shift from daylight saving time to standard time in November, when the clocks go back an hour, leading to sunrise and sunset being experienced at an earlier time, led to a sudden increase in the amount of driving during darkness. Peak traffic volume also shifted from before sunset in October to during sunset in November. The records showed that collisions between deer and cars in the US rise by 16 per cent in the week following the autumn clock change.
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Read more: Daylight saving time linked to an increase in traffic accidents
“The animals haven’t changed their activity patterns at all. It’s just there’s just more traffic on the roads in the periods that they’re vulnerable,” says Cunningham. “The change in time system causes sunset to come forward an additional hour, relative to clock time. That means that irrespective of seasonal changes in day length, there is more traffic at night during standard time compared to if clocks remained on daylight saving time.”
Almost 10 per cent of collisions with deer tend to occur in a period of two weeks around the autumn clock change, which the team says is 2.5 times greater than would be seen if collisions were uniform across the year. The animals are more active than usual around that time of year, however, because it is their breeding season.
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Deer are the largest species of animals commonly hit by cars in the US and collisions generally cause enough damage that they are reported to insurance companies, making data easy to collect. But Cunningham says that activity patterns for smaller mammals are probably similar and collisions with them often aren’t recorded, meaning that the ecological benefit of scrapping time changes, which are observed in much of North America and Europe, could be huge.
Cunningham says there could also be negative social factors that would complicate any policy decision relating to ending daylight saving changes. “It would require a very nuanced cost-benefit analysis of all of the different ways in which time zones can affect society,” he says. “They’re both going to have benefits and they’re both going to have costs and optimising that is really important.”
Journal reference: Current Biology, DOI: 10.1016/j.cub.2022.10.007
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