This year, americans will fill about 60 million prescriptions for sleeping pills, including ambien, the drug that made headlines last month when kerry kennedy crashed her car on a highway. Did you... See More
This year, americans will fill about 60 million prescriptions for sleeping pills, including ambien, the drug that made headlines last month when kerry kennedy crashed her car on a highway. Did you know that some sleeping pills can stay in your body for as long as 12 hours? Sole we wondered when is it safe to drive. We want the to see first hand. Abc's lisa stark taking a ground breaking test. Reporter: You are looking at the first test of its kind ever done in the u.S. I drifted off there for a second. Reporter: I am in a driving simulator, swerving all over the road, nearly hitting a pedestrian, barely keeping my eyes open. Ah. Reporter: I am not drunk. I'm testing another type of impairment. Driving on the nation's most popular sleeping pill, an, and its generic version zolpidem. There are cases all over the country. Those who pop the pill on the way home, or try to drive too soon. And perhaps the most terrifying of all -- this new jersey woman had no idea she was even driving. She had taken ambien and alcohol, gone to bed, ended up on the road. A frightening case of sleep driving. You hit something with your car. Reporter: With 60 million annual prescriptions for sleeping pills in the u.S., there's increasing concern. That's what brought us to the university of iowa andhe nation's most sophisticated driving simula researchers watch my every move. We can see the speed of your vehicle. We have cameras pointed at your eyes and we're tracking the movement of your pupils. Big moment, take my sleeping pill. The drug is designed to act fast. Very fast. So it's been a little over 30 minutes since lisa took the medicine. Reporter: Only 30 minutes. I'm a little dizzy, but i think I can do it. Reporter: I'm wrong. Am I on the wrong side of the road? Reporter: I am awake enough to know something's not right, but I can't help swerving all over the road. So this is very dangerous. She's really stopped blinking. Reporter: An indication my brain thinks I'm asleep and that I don't need to blink. She's really just zoned out. She's sort of in la la land. Reporter: After a nap, the maximum ambien stupor, 90 minutes in, I try again. Oh that wasn't so good of a turn. I totally fell asleep again. Reporter: I tried to make a turn -- and then I smash into a big rig. If she was in a real car, this would be the end. Um, that was like being in never, never land. Reporter: After four hours, two-thirds of the drug gone, i think I'm okay, but see this red light, right through it. People who are impaired don't realize how impaired they are. They think they are driving fine but they are not. Reporter: And remember the woman who never realized she was behind the wheel? I drove three times impaired but recalled only two. And the minute the car was turned off, I was out like a light. Now, the pill's developer says it stands behind the safety of ambien when taken as directed, and there is a clear warning on the drug to make sure you get a full seven or eight hours sleep. But the pill doesn't really clear your system entirely for a good 12 hours, so diane, the label also warns do not drive until you fell fully awake. Fully awake. But what about these cases of people who didn't even know they were driving? What's behind that? Well, what the manufacturer says is that they're abusing the drugs. They're using alcohol with it. They're taking too many pills. And it can happen with any sleeping pill. You have to be very careful. But you didn't remember one time you took the test? They told me I took four drives, but but apparently i did. All right. Lisa stark awake and alert tonight. Thanks so much for that.
This transcript has been automatically generated and may not be 100% accurate.