Asleep-at-the-wheel drivers are a deadly menace. But the drowsy-driver detectors that have come out of some labs have serious flaws. Lane monitors sense when a car is drifting astray, but by then the driver is already asleep. Eye-blink and head-bob sensors work well, but some people can actually fall asleep with eyes open and heads upright. The Johns Hopkins Applied Physics Laboratory has built a drowsy-driver detector that promises to be less easily fooled because it looks at overall body motion plus eye blinks. A windshield-mounted radar device scans the driver and detects motion, feeding the data to a program created by a team led by Henry Kues. When the driver first sits in the car, the program takes a baseline measurement of such normal movements as fidgeting, radio tuning and head turning. When movement slows and ceases-an indication that sleep is imminent-the program focuses on eye blinks. The lab is trying to license the technology.