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NEW YORK (CBSMiami) – Americans aren’t getting enough sleep and a new study finds drowsy driving is leading to many more car crashes than previously thought.

Jennifer Pearce knows that first hand. Ten years ago her sister Nicole, a college freshman, was returning from a ski trip with friends when everyone in the car fell asleep. They slammed into a tree. Nicole was rushed to the hospital but didn’t survive.

“None of us made it to the hospital in time to say goodbye,” said Pearce. “It just never dawned on me that we would lose her.”

Previous government estimates put drowsiness as a factor in one to two percent of accidents. But a new study from AAA found that number is much higher.

After analyzing thousands of dash cam videos, researchers determined nearly ten percent of crashes can be blamed on drowsy driving.

“I think that underscores the significance of this safety concern on the road,” said AAA’s William Horrey.

Getting only four hours of sleep at night can have an effect similar to drunk driving.

“You might have sluggish responses, you might not be able to keep the vehicle in the lane as well as you should,” said Horrey.

Government figures show 35 percent of U.S. drivers don’t get the recommended minimum of seven hours of sleep every night.