Car crashes with deer increase after time change

A Clarkson University professor’s research shows that the rate of car/deer crashes goes up at the end of Daylight Saving Time. Kara Dry/Watertown Daily Times

When the time shifts from Daylight Saving Time to Standard Time on Nov. 7, one Clarkson University professor has discovered one more thing to lose sleep over — the number of car crashes with deer go up around the time of the change.

Tom A. Langen, a professor of biology at Clarkson, published a paper in the Journal of Environmental Management in August. The paper, “Effect of Daylight Saving Time clock shifts on white-tailed deer-vehicle collision rates,” states that, “Daylight Saving Time (DST) 1-h clock-shifts around the spring and fall equinoxes at temperate zone latitudes are associated with increased vehicle accidents, attributed to driver error caused by disrupted sleep patterns and changes in visibility during peak driving times.”

Mr. Langen also published at article on the topic in Conversation, a nonprofit, independent news organization that publishes articles written by academic experts.

Mr. Langen’s primary research is about the environmental impacts of roads and how to reduce them, which includes mortality rates on small mammals and reptiles.

A graduate student of Mr. Langen’s from Spain, Victor Colino-Rabanal was interested in looking at patterns comparing Europe and North America regarding animal/vehicle collisions.

Mr. Langen, Mr. Colino-Rabanal and another graduate student, Nimanthi Abeyrathna analyzed more than 86,000 deer-vehicle collisions involving white-tailed deer in New York state using police records over a three-year period, 2005-2007.

“We were interested in when do accidents happen most frequently,” Mr. Langen said. “Our first project was looking at it related to the moon. Some things are really obvious. More accidents happen at dusk than during daylight or at nighttime but it turned out there were more accidents for white-tail deer during a full moon.”

During a full moon, especially a new moon, deer move farther away from cover, Mr. Langen said.

“But that led to me thinking about Daylight Saving,” Mr. Langen said.

In the piece in Conversation, Mr. Langen wrote, “In New York state, the peak number of deer-vehicle accidents occurs in the last week of October and first weeks of November. There are over four times as many deer-vehicle accidents during that period than during spring.”

That time period is also when Daylight Saving Time ends.

“Shifting the clock one hour back means more commuters are on the road during the high-risk dusk hours. The result is more cars driving at the peak time of day and during the peak time of the year for deer-vehicle accidents,” Mr. Langen wrote.

The clock shift in the spring does not have as big an impact on the rate crashes, Mr. Langen said.

The best defense for car/deer crashes is to be alert and to drive slower, Mr. Langen said.

“So you have more time to react,” he said. “At night we tend to drive faster than our headlights and our reaction times can be.”

If one deer crosses, there are likely more deer about to cross, he said and don’t swerve to avoid a deer. The deer is going to move, but you can’t tell where it will move and swerving can cause crashes with other vehicles.

“Slow down as much as you can and brace yourself,” he said.

The Insurance company State Farm, which Mr. Langen cites in his article in Conversaion, found that U.S. drivers on average have a 1-in-116 chance of hitting an animal in a given year. In New York that rate is 1-in-133.

The Conversation article can be found at and the Journal of Environmental Management paper can be found at

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Johnson Newspapers 7.1

St. Lawrence/Franklin County Editor

Slowly self-propelled. Two-time cancer survivor. Nearly 30-year newspaper veteran.

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(1) comment


"attributed to driver error" almost funny.

Not worth noting that deer are entering their "rut" at this time of year which increases activity and nocturnal movement ?

Almost like spring time adjustment is the cause for maples to start producing sap

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