Traffic accidents are a serious side effect of Daylight Savings Time, reports TIME.

When you’re enjoying your extra hour in bed Sunday morning, spare a thought for what that 60 minutes might cost.

While some dislike the seasonal shifts of Daylight Saving Time (DST) for the minor inconvenience to their sleep cycles and busy schedules, there’s a more serious side to the scheme: the loss of an hour of afternoon sunlight when it ends—as it does this weekend—may increase the likelihood of traffic accidents.

“Darkness kills and sunlight saves lives,” said University of Washington Law Professor Steve Calandrillo, who has studied the effectiveness of different DST policies. “The question is ‘when do you want sunlight?’”