Fatigue causes a staggering 20 per cent of road accidents in the US, rather than the 2 to 3 per cent previously estimated, researchers claim.
A 100-car naturalistic driving study conducted by the Virginia Tech Transportation Institute in the US found that fatigue is a cause of 20 per cent of crashes, rather than the 2 or 3 per cent previously estimated based on surveys, simulator studies, and test tracks.
The study also found 18 to 20-year-olds account for significantly more fatigue-related crashes than any other age group.
Adolescents' sleep patterns shift to later hours; however, 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," said Charlie Klauer, group leader for teen risk and injury prevention at the transportation institute's Center for Vulnerable Road User Safety.
"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," she said.
"The study allowed us, for the first time, to observe driver behaviour just prior to a crash. In 20 per cent of all crashes and 16 per cent of all near crashes, the driver was showing fatigue.
"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. This was not just yawning. The drivers were asleep," said Klauer.
One-hundred drivers who commuted into or out of the Northern Virginia/Washington, DC, metropolitan area were initially recruited as primary drivers to have their vehicles instrumented or receive a leased vehicle instrumented for the study.
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.
The total number of subjects who were involved in fatigue-related crashes and near-crashes was 38, with 11 drivers accounting for 58 per cent of all the fatigue-related crashes and near-crashes.
