Two out of every five drivers (41%) admit to having fallen asleep at the wheel at some point, with one in 10 saying they’ve done so in the past year, according to a new AAA Foundation for Traffic Safety study. More than a quarter of those surveyed admitted that in the previous month they drove despite being so tired that they had difficulty keeping their eyes.

Eighty-five percent of drivers surveyed felt it was “completely unacceptable” for someone to drive if they are so tired they are having trouble keeping their eyes open. Unfortunately, drivers may not always be aware of the effects of fatigue resulting from a lack of sleep.

“When you are behind the wheel of a car, being sleepy is very dangerous. Sleepiness decreases awareness, slows reaction time, and impairs judgment, just like drugs or alcohol, contributing to the possibility of a crash,” said AAA Foundation President and CEO Peter Kissinger. “We need to change the culture so that not only will drivers recognize the dangers of driving while drowsy but will stop doing it.”

A new analysis of National Highway Traffic Safety Administration crash data estimates that about one in six (16.5%) deadly crashes, one in eight crashes resulting in occupant hospitalization, and one in 14 crashes in which a vehicle was towed involve a driver who is drowsy. These percentages are substantially higher than most previous estimates, suggesting that the contribution of drowsy driving to motor vehicle crashes, injuries, and deaths has not been fully appreciated.

David Cloud, CEO of the National Sleep Foundation, added, “It is shocking to consider that one quarter of drivers admit to operating a vehicle in the last month in an incapacitated state.” The National Sleep Foundation has been championing better drowsy driving awareness and education since 1991. Cloud adds, “We applaud AAA’s work to elevate this issue for public scrutiny and action.”