There is no shortage of public service messages warning against driving while intoxicated. But scant attention is paid to the dangers of falling asleep behind the wheel -- to which teenage drivers are particularly vulnerable.

• Exhaustion plays a part in more than 100,000 car crashes each year, estimates the National Highway Traffic Safety Administration.

• Drivers age 15 to 24 account for more than half of those, studies show.

• Experts say that beginning at about age 15, youngsters need more sleep than younger children or older adults -- a minimum of nine hours a night.

• Yet teenagers sleep an average of six hours a night -- rising early to get to school on time and going to bed late due to part-time jobs, school functions, homework, sports activities and socializing.

The three-hour deficit accumulates over several days and too often results in their dozing while driving. Unlike adults, teens are less experienced drivers and fail to recognize their limits, as adults would do.

The NHTSA and the National Center on Sleep Disorders are waging a joint education campaign targeting teenagers this school year.

Source: Laura Sessions Stepp, "Asleep at the Wheel," Washington Post, February 6, 2000.