Published: Nov 09, 2010 12:05 PM EST
Updated: Nov 09, 2010 9:06 AM EST

WASHINGTON (AP) - Sleep deprivation can be deadly on the highway.

A study by the AAA Foundation for Traffic Safety finds that more than 40 percent of drivers admit to having fallen asleep at the wheel at some point. One in ten said they've done so in the past year.

The foundation says drowsy driving is a contributing factor in 17 percent of all fatal crashes. And yet, more than a quarter of the drivers surveyed admitted they drove despite being so tired that they had difficulty keeping their eyes open.

Foundation spokesman Dan Bleier (BLY'-ur) says "just like drugs or alcohol, sleepiness can impair drivers' awareness, reaction time and judgment."

He recommends plenty of sleep the night before a long road trip. And even though the trip might take a little longer, Bleier urges frequent rest breaks -- even short power naps -- every 200 miles or so.