Tired drivers are causing 20 percent of crashes and 16 percent of near-crashes, according to a recent study.
Previous estimates put driver fatigue as a factor in only 2 or 3 percent of crashes, based on surveys, simulator studies, and test tracks.
The Virginia Tech Transportation Institute conducted a a 100-car naturalistic driving study that allowed researchers, for the first time, to observe driver behavior just prior to a crash.
The study also concluded that 18- to 20-year-olds account for significantly more fatigue-related crashes than any other age group.
Although adolescents’ sleep patterns shift to later hours as they age, the school day still tends to start early, resulting in daytime sleepiness. Older drivers can face similar issues with late nights and early work times, but have more experience coping with moderate fatigue.
“One of the most important results from the 100-car naturalistic driving study was the degree to which fatigue is a cause of accidents,” Charlie Klauer, group leader for teen risk and injury prevention at the transportation institute’s Center for Vulnerable Road User Safety, said in a statement. “A finding that surprised people is the prevalence of fatigue during the day. We found significantly more crashes/near crashes due to fatigue during the day than at night.”
One-hundred drivers who commuted into or out of the Northern Virginia/Washington, D.C., metropolitan area were initially recruited as primary drivers to have their vehicles instrumented or receive a leased vehicle instrumented for the study. Since other family members and friends would occasionally drive the instrumented vehicles, data were collected on 132 additional drivers.
“We saw eye-lid closure, head bobbing, severe loss of facial musculature, micro sleep – which is when your eyes drift shut and then pop up,” Klauer said. “This was not just yawning. The drivers were asleep.”
Researchers selected a larger sample of drivers below the age of 25, compared to the total population of drivers, and a sample that drove more than the average number of miles.
Sensors included five video channels, forward and rearward Vorad radar units, accelerometers, lane tracking software and an in-vehicle network sensor. The cameras were mounted unobtrusively in order to facilitate naturalistic driving behavior.
Researchers viewed more than 110,000 events in order to validate 10,548 events – specifically, 82 crashes, including 13 where the data was incomplete; 761 near crashes; 8,295 incidents, such as braking hard for slowing or stopped traffic; and 1,423 non-conflict events, such as running a stop light with no traffic present.
In addition, 20,000 randomly selected six-second segments of video were viewed. Incidents of moderate to severe driver fatigue were noted, providing an estimate of the amount of time drivers were fatigued but were not involved in a crash or near-crash.
The total number of subjects who were involved in fatigue-related crashes and near-crashes was 38, with 11 drivers accounting for 58 percent of all the fatigue-related crashes and near-crashes.
“Applying the findings to the population at-large, these results suggest that drivers are at a four times greater risk of a crash or near-crash if they choose to drive while fatigued,” Tom Dingus, director of the Virginia Tech Transportation Institute, said in a statement. “That suggests that about 12 percent of all crashes and near-crashes in the population are attributable to fatigue.”
The 100-Car Naturalistic Driving data set was collected in 2003 and 2004 and has been mined numerous times since.
