Pretty much everyone is aware of the dangers of drunk driving, but did you know that a motorist who's had less than five hours' sleep in a 24-hour period has a crash risk comparable to one who's legally drunk? Or that drowsy driving is blamed in more than 5,000 fatal crashes annually?

Americans just don't get enough sleep. According to a recent study, a near-unanimous 97 percent of motorists categorize drowsy driving as completely unacceptable.

Ironic, then, that 1 in 3 also admit that in the past month they'd driving when they could barely keep their eyes open.

Symptoms of drowsy driving can include trouble keeping your eyes open; drifting between lanes; difficulty focusing; daydreaming or disconnected thoughts; frequent yawning; forgetting the last few miles; and missing signs or exits.

But more than half of drivers involved in fatigue-related crashes experience no symptoms before dozing off. Here's how to avoid being asleep at the wheel:

• Get at least six hours' shuteye the night before a long trip.

• Travel when you'd normally be awake, resisting the urge to drive through the night.

• Take a break every two hours or 100 miles.

• Avoid heavy foods and medications that cause drowsiness.

Pull over at a rest stop and nap if you get sleepy — you'd be surprised how refreshing a 10- or 15- minute catnap can be.