CHICAGO (CBS/AP) — The number of people killed in crashes caused by drivers running red lights reached a 10-year high in 2017, according to a new study by the AAA Foundation for Traffic Safety.

The study found 939 people died in 2017 as a result of someone ignoring a red light, up 31% from a low of 715 in 2009.

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Red light crash fatalities rose for the fifth consecutive year in 2017, and AAA said it’s hard to pinpoint why.

AAA isn’t sure why the numbers are on the rise or why they have increased at a far higher rate than overall U.S. roadway deaths. Since 2012 the overall number of highway fatalities rose 10%, far short of the 28% increase in red-light running deaths.

The 939 fatalities in red light crashes were the highest death toll since 2008, when the U.S. was hit by the Great Recession. AAA said more people are driving since then so that could be a cause, but researchers said there is one glaring issue.

“The problem is drivers are distracted, they’re impatient, and they’re reckless, and they’re making the decision to run a red light instead of safely stopping,” said AAA spokesman Doug Shupe.

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In its analysis, AAA also found that 28% of crash deaths at intersections with signals happened because a driver ran a red light.

Researchers also said some traffic lights might not be timed optimally, perhaps with yellow lights that are too short.

The automobile club recommends that governments increase use of red light cameras directly supervised by authorities in order to boost enforcement where needed and not to raise revenue.

It also says drivers should prepare to stop as they are entering an intersection and tap their brakes while approaching a light to warn other drivers of a possible stop. AAA also recommends waiting a second after a light changes to green before proceeding and checking to make sure crossing traffic has stopped.

For pedestrians and cyclists, AAA recommends taking a few seconds to make sure traffic has stopped before crossing a street. It also says to be visible, make eye contact with drivers and stay alert by not wearing headphones while walking or riding.

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