Asleep At The Wheel: Drivers Unaware Of How Drowsy They Are

It’s something that most drivers experience but may not realize until it’s too late – feeling drowsy – which plays a role in traffic crashes, injuries, and deaths. Although underreported in government statistics, previous research by the AAA Foundation for Traffic Safety has estimated that 16% to 21% of all police-reported fatal vehicle crashes likely involve drowsy driving. And now, new Foundation research finds that drivers may underestimate their drowsiness, leading them to stay behind the wheel instead of stopping for a much-needed break.

“Being drowsy while driving is a dangerous form of impairment, and it does not resolve or improve with continued driving,” said Dr. David Yang, the Foundation’s president and executive director. “Our goal is to help drivers learn to heed the early warning signs of drowsiness so they can stop, rest, and then continue their journey as safely as possible.”

Drowsiness refers to a state of increased tendency to fall asleep. Beyond the danger of falling asleep at the wheel, drowsiness also impairs drivers by reducing their alertness. Crashes caused by drowsy driving tend to be severe because the driver may not attempt to brake or swerve to avoid a collision, so the resulting impact occurs at a high rate of speed. A drowsy driver may also be startled and lose control of the vehicle.

Researchers designed a 150-mile simulated nighttime highway driving experiment for the study. Every 20 miles, there was a simulated “rest area” at which participants could stop, leave the driving simulator, walk around, nap, drink coffee, or eat a snack. A monetary incentive encouraged drivers to complete the drive as quickly as possible while incentivizing them to avoid crashing. Researchers used a brief survey to gauge how drowsy drivers felt and measured the percentage of time their eyes were closed to gauge sleepiness.

Please refer to the fact sheet or technical report for methodology details (see above).