This year, americans will fill about 60 million prescriptions for sleeping pills, including ambien and highway cops are fast learning that the innocent pursuit of sweet dreams can lead to nightmare... See More
This year, americans will fill about 60 million prescriptions for sleeping pills, including ambien and highway cops are fast learning that the innocent pursuit of sweet dreams can lead to nightmare scenarios on the open road like kerry kennedy's crash just last month. And these drugs can stay in your system and affect motor skills for up to 12 hours. To show you exactly how they affect your motor skills, abc's lisa stark turned herself into a sleepy guinea pig. Reporter: Are drinking and driving, it's terrifying, alcohol has long be a killer on the roads. Ah! Stop, stop, stop. Reporter: Now a new and growing hazard, a substance usually not detected and used every day. Ambien, the nation's most popular, 40 million annual prescription. In new jersey police arrested this woman who appeared drunk. It wasn't just alcohol. She had popped ambien, gone to bed had no memory of getting behind the wheel. You hit something with your car. Reporter: In texas a woman who mixed wine with ambien also ended up unknowingly on the road. She runs over a family in their yard, severely injuring an 18-month-old. She got probation. Her lawyers argued she had no intention of driving. She took the sleeping pill, expected to go to sleep. Researchers say it's important to understand how the brain functions when it's on sleeping medication. The results eye-opening to say the least. I'm driving a car and I clearly shouldn't be. Weaving in and out of lanes. But don't worry, we won't put anyone's life in danger. For our road test we came to the university of iowa, to the nation's most advanced driving simulator. Where I am the first person to undergo this simulation while under the influence of ambien. We can expose people to things like alcohol and drugs and study how they affect people's driving. Reporter: Omar ahmed is the director here. Inside a chevy malibu. From the control room, researchers simulate my virtual road and monitor my every move. We can see the speed your vehicle. We have cameras pointed at your eyes and track your movement. Reporter: Before I take the sleeping pill, I'm a pretty good driver. And I pass the sobriety test with perfect coordination. Then the pill is designed to work quickly, very quickly. There's a clear warning with ambien, in fact, all sleeping pills for at least seven to eight hours. Do not drive until you feel fully awake. But we know that doesn't always happen. And it's not just sleep driving. Some impaired drivers report taking the medication just 15 minutes before being pulled over. Others, including kerry kennedy, say they may have popped a pill by mistake before hitting the road. We're going to wake her up and ask her to do her first drive. Lisa. Reporter: It's just 30 minutes after I've taken the pill. I start swerving immediately. Lisa's now driving in the passing lane. This is very dangerous. She literally stopped blinking. She's zoned out. Reporter:90 minutes in, the drugs a at their peak, and I'm back on the road. I was so drowsy, I swiped a big rig. No. If she was in a real car, this would be the end. Reporter: After my disastrous drive, I attempted the sobriety test once more. Closed your eyes. No it wasn't? It was? Reporter: And one more attempt in the car, four hours after taking my sleeping pill. See that red light? I bl right through it. Remember that new jersey woman, attorney richard uselin usually used the first ambien defense to get her off. When you're taking sleeping aids you're playing russian roulette because you would not necessarily have any indication whatsoever that you can actually sleep drive and be a danger to yourself and others in this instance. Reporter: The drug's developer ambien said the drug has a 20-year track record is perfectly save when taken as directed. They point out that sleep driving is very drive and also as a result of drinking alcohol. As I found out, it's not a medication to be taken lightly. As soon as the car turned off, i did, too. For "nightline," lisa stark, coralville, iowa. Our thanks to lisa for that.
This transcript has been automatically generated and may not be 100% accurate.