Prolonged nighttime driving can be just as hazardous as driving drunk, according to European researchers who examined the impact of fatigue on performance behind the wheel.
Researchers at Utrecht University in the Netherlands found that driving for just three hours at night was similar to being intoxicated, and even two hours after dark was like being buzzed.
In conducting the test, the researchers had 14 men, aged 21 to 25, drive under supervision at night from 3 a.m. until 5 a.m., 1 a.m. until 5 a.m. and 9 p.m. until 5 a.m. They were to drive at a constant speed of 80 mph while staying centered in the lane. Their performance was monitored and recorded, and deviations from the center line measured.
The academics, led by Dr. Joris C. Verster, found remarkable parallels with drunk driving. Two hours of nighttime driving resulted in the same errors experienced with a blood alcohol content of 0.05. Performance was on par with a BAC of 0.08 percent after three hours. And 4.5 hours at the wheel in the dark was akin to 0.10 percent. Opening the window for a blast of cold air or cranking up the stereo had little effect, they said.
The report, published in the Journal of Sleep Research, says drivers should recognize the risk.
"Our data show that drivers should take sleepiness behind the wheel seriously," they say in the report. "It is one of the primary causes of accidents on motorways. Yet drivers themselves are sometimes unaware of sleepiness, reduced alertness and corresponding impaired driving."
The researchers estimate that as much as 20 percent of vehicle accidents in industrialized countries can be attributed to fatigue. They suggest traffic laws bar us from driving for more than two hours at night, though they concede that would be difficult to enforce.
Photo of the night vision system in the BMW 7-Series: BMW