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Still, Mr. Hall said: ''There has traditionally been knee-jerk resistance in the automotive industry to safety changes, and this issue, I'm sure, is no exception. We need advocacy groups to increase awareness and lobby for the necessary changes.''

At last week's conference, the National Summit to Prevent Drowsy Driving, held in Washington at the National Academy of Sciences, Dr. David Dinges, an expert on sleep and body clocks from the University of Pennsylvania School of Medicine, said dozens of claims had been made for devices promoted as ''online monitors of drowsy driving.''

They include a sensor mounted on the roof of the car to detect when the driver's head falls over, a wrist sensor that monitors heart rate, a sleep watch that measures muscle activity, a device worn on the temple that registers eye blinks and electrodes that record brain waves.

The problem, Dr. Dinges said, is finding something that works reliably for everybody, or nearly everybody, in nearly every situation. The head-droop sensor, for example, cannot tell the difference between a driver who is falling asleep or one who is changing the radio dial, glancing at a map or picking up a sandwich.

To date, he said, the device that has proved most reliable in tests is an infrared gadget that detects slowly drooping eyelids, a hallmark of impending sleep. The device, developed at Carnegie Mellon University, pulses two wavelengths of infrared light off the face and bounces them back to a camera on the dashboard, which records a dark face with eyes shining like a cat's and can detect how open the eyes are.

This ''co-pilot'' device, he said, works for nearly everyone, but it too has limits: it does not work as well in bright sunlight or with people wearing certain kinds of lenses. Nor will it work for those rare cases who can fall asleep with their eyes open.

Also being used in some trucks is a tracking system that can detect lane deviations -- when the vehicle has drifted off the tire tracks worn into the roadway -- with a black box that can provide a permanent record should an accident occur, Colonel Belenky said.

''One can imagine all sorts of possibilities for detecting drowsy driving and warning people that they are not fit to drive,'' he said, including a means of measuring increased blood levels of interleukin-6, a substance that correlates well with sleep deprivation.

''Once you have a good monitor of drowsiness, the next issue is how to give this information to the driver,'' Dr. Dinges said. ''Do you use lights, tones, a female voice, release the odor of peppermint or menthol, or what?'' He was not impressed with the idea of squirting ice water. ''And once you sound the alarm, will people continue to drive?'' he wondered, just as many drivers ignore the warning beep of an unbuckled seat belt.

Many major highways now have rumble strips on the right side of the road to awaken drifting drivers. But these cannot prevent a startled sleeping driver from overcompensating and crashing. Nor will they stop someone who drifts to the left or plows straight ahead into a slower vehicle or stopped traffic.

While the best countermeasure to sleepy driving is to pull off the road and nap, Dr. Dinges noted that ''a lot of people don't feel safe doing that.'' In one survey of women who drive, 95 percent said they would not pull into a rest stop to nap. Furthermore, Dr. Dinges said, rest areas are too few and far between on most roads. ''How do we provide frequent safe areas for people to get off the road and sleep, especially those who are driving alone? That is the real public policy issue.''

A recent study of truck stops revealed 24,000 too few slots for trucks, and the number of trucks on the road continues to increase, Dr. Dinges said. At some truck stops, officers routinely waken drivers and tell them to move on to make room for more trucks.

Photo: Melissa Cullen was hurt and her father was killed after their car was hit by a sleep-deprived driver in Delaware. (National Sleep Foundation)(pg. F1) Chart: ''Sawing Logs Behind the Wheel'' A poll by the National Sleep Foundation finds that 51 percent of motorists have driven while feeling drowsy in the past year, and 17 percent have dozed off. DRIVING WHILE FEELING DROWSY 71% of 18-29 year-old drivers 56% of male drivers 45% of female drivers 52% of 30-64 year-old drivers 19% of drivers 65 and older FATAL CRASHES IN WHICH DROWSINESS IS A FACTOR The National Highway Traffic Safety Administration estimates that drowsiness accounts for about 2 percent of fatal-crash factors. Factors are not necessarily the cause of the crash, but are reported by the police as having played a role. Graph shows crash comparisons since 1991. (pg. F6)