DRIVER FATIGUE TRIGGERS HOLIDAY ACCIDENTS.

Memorial Day, the Fourth of July, and Labor Day are coming, bringing added leisure time. There is a dark side, though, to these icons of the American vacation season--inevitable news reports updating highway accident death tolls. Although heavy travel volumes certainly play a role in the high accident rates, especially over busy three-day weekends, most experts agree that another factor is likely a cause--increased driver fatigue attributed to lengthy driving hours, lack of sleep, and the demands of holiday activities.

A long, refreshing rest may be the only real solution to the dangers of driving while groggy, but, human nature being what it is, many drivers will push the boundaries of endurance and risk behind the wheel. This is a problem expected to grow worse as America's bustling, 24-hour, work-hard, play-hard culture adds to the national sleep deficit. While science has yet to find a fail-safe solution for "asleep at the wheel" driving, research is providing important clues on the biomechanics of driver fatigue and paving the way for development of onboard alarm systems capable of rousing a driver who is dozing toward catastrophe.

What is known for certain is that driver fatigue already poses one of the leading threats to safety on the nation's roads. According to estimates from the National Highway Traffic Safety Administration, at least 100,000 vehicle crashes, 71,000 injuries, and 1,500 fatalities each year can be directly attributed to it. In addition to human suffering, these crashes are estimated to rack up about $12,500,000,000 in costs related to diminished productivity and property loss. Others consider these estimates to be conservative, asserting that driver fatigue plays a significant role in the nearly 1,000,000 annual crashes that are generally attributed to driver inattention.

"It's fairly obvious that people shouldn't be driving when their eyes are closed, but our research suggests that fatigued drivers become increasingly susceptible to accidents long before they actually fall asleep at the wheel," notes John Stern, a professor of psychology at Washington University in St. Louis (Mo.) and one of the world's leading authorities on eye blinks and driver fatigue. For more than a decade, he and others have explored physiological characteristics associated with fatigue and the onset of sleep in the hope that a "gadget" could be devised to recognize the telltale signs of driver fatigue and issue a life-saving warning. Much of this research has focused on the trucking industry because commercial operators have more incentive to invest in and utilize the warning devices. Stern estimates that the devices will initially cost several thousand dollars per vehicle, but he expects the cost to drop as the gadgets become more readily available for use in passenger cars.

What measures of the fatigue are these devices most likely to monitor? Scientists contend that long blinks and eye closures occur too late in the behavioral chain to be useful as predictors of impaired performance because a driver with closed eyes may already be in the danger zone.

"Alerting systems that detect late-stage sleep onset will be of marginal use because danger arises much sooner as alertness fades and driver ability diminishes," Stern points out. "To be of much use, alert systems must detect early signs of fatigue, since the onset of sleep is too late to take corrective action." Researchers are attempting to pinpoint various irregularities in eye movements that signal oncoming mental lapses--sudden and unexpected short interruptions in mental performance that usually occur much earlier in the transition to sleep. If these mental lapses can be identified and predicted, they may prove much more useful in providing timely advance warning to a driver edging toward drowsiness.