AUSTIN, Texas -- Crashes involving drowsy drivers are more dangerous than previously thought, according to an AAA study.

Researchers used Dashcam video from more than 700 crashes. They found that drivers often have trouble detecting drowsiness as a cause for a crash.

"Drivers need to be aware that when they don't get enough sleep they're not only putting themselves in risk but everyone else on the road. Just missing a few hours of sleep each night quadruples your risk for a crash, so this is a serious problem,” said Daniel Armbrunster, with AAA.

The CDC reports 35 percent of U.S. drivers sleep less than the recommended minimum of seven hours a night. In a recent AAA survey, 96 percent of drivers say they view drowsy driving as a serious threat to their safety.