Driving while drowsy continues to be a significant problem. It affects drivers of all age. I'm just referring to drivers who fall asleep at the wheel - also drivers who are sleep deprived enough to impair their reaction times on the road. This level of impairment can be difficult for a driver to recognize. Therefore a sleepy driver may push on, continuing to drive because they have not actually fallen asleep.
Here is a link to recent statistics from the National Highway Traffic Safety Association citing that approximately one in four motor vehicle accidents is due to drowsy driving. Someday, sleep researchers may come up with a reliable and simple test of sleepiness that drivers could use to determine if they shouldn't drive. They could take a brief nap first. Although, this all may be moot if Google makes driver-less cars a reality.