Many Americans admit they've done it, but safety experts say drowsy driving is a problem motorists are just starting to wake up to.
A fatigue expert on the National Transportation Safety Board says drowsy driving can be as bad as drunken driving. Police today can easily determine how much alcohol is in a driver's blood or whether someone has taken illegal drugs. But proving a driver's drowsiness is not as easy.
Federal statistics show more than 11,000 deaths were attributed to drowsy driving from 2000 to 2010.