WASHINGTON, D.C. — Truckers have always been accused of driving beyond their limits but a new study confirms what many truck drivers already knew – it’s the four-wheelers who are the biggest threat.

The study, commissioned by the National Sleep Foundation (NSF), indicates one in five motorists admit to having fallen asleep at the wheel in the past year.

NSF director, Richard Gelula, says “I think in our society we are quite used to denying our tiredness. We believe that sleep is something that we can cheat on.”

The foundation likens driving tired to driving drunk.

“It’s a form of impaired driving, really,” says Judith Stone, president of Advocates for Highway and Auto Safety. “It’s in the same kind of category as drunk driving.”

According to the U.S. National Highway Traffic Safety Administration, tired drivers cause 100,000 accidents each year, resulting in more than 1,500 deaths.

Young men are the most likely to drive while tired.