Something that most drivers experience but may not realize until it’s too late – feeling drowsy – plays an undetermined 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 new Foundation research finds that drivers may underestimate their drowsiness, leading them to stay behind the wheel rather than stopping for a much-needed break.
"Motorists need to understand the dangers of drowsy driving and that it is a condition that does not resolve or improve with continued driving," said Terri Rae Anthony, safety advisor, AAA East Central. "Our goal is to help drivers learn to pay serious attention to 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.
Levels of drowsiness generally increased throughout the simulated highway driving experiment. Participants were usually aware that they were drowsy, but their perceptions of the extent of their sleepiness were not always accurate and affected decision-making.
- When drivers rated their level of drowsiness as low, 75% of them were, in fact, moderately or severely drowsy.
- Even when drivers’ eyes were closed for 15 seconds or longer over a one-minute window— indicative of severe drowsiness—one in four still rated their drowsiness as low.
- Drivers rarely took breaks unless they perceived that they were extremely drowsy.
- Even when drivers recognized they were exceedingly drowsy, they still declined 75% of their opportunities to take breaks and kept driving.
Please refer to the fact sheet or technical report for methodology details.
The results demonstrate a need to help drivers recognize how drowsy they are. Knowing the warning signs of drowsiness can help drivers avoid dozing off behind the wheel. The most common symptoms include:
- Having trouble keeping your eyes open
- Drifting from your lane
- Not remembering the last few miles driven
While the signs of drowsiness should never be ignored, drivers must not wait for their bodies to sound the alarm. They should prioritize sleeping at least seven hours before hitting the road.
AAA recommends that drivers:
- Travel at times of the day when they are normally awake
- Avoid heavy foods
- Avoid medications that cause drowsiness or other impairment
For longer trips, drivers should:
- Schedule a break every two hours or every 100 miles
- Travel with an alert passenger and take turns driving
- Do not underestimate the power of a quick nap. Pulling into a rest stop and taking a quick catnap, at least 20 minutes and no more than 30 minutes, can help keep you alert on the road
AAA supports the development of vehicle technology that can passively monitor drivers for impairment and prevent or limit vehicle operation when needed. The 2021 Infrastructure Investment and Jobs Act requires NHTSA to create testing standards for this kind of technology that can detect driver impairment, including that caused by drowsiness, medical impairment or drugs, including alcohol.
About AAA Foundation for Traffic Safety
Established in 1947 by AAA, the Foundation for Traffic Safety is a nonprofit, publicly funded 501(c)(3) charitable research and educational organization. The AAA Foundation's mission is to prevent traffic deaths and injuries by researching their causes and by educating the public about strategies to prevent crashes and reduce injuries when they do occur. This research informs the development of educational materials for drivers, pedestrians, bicyclists and other road users.
AAA East Central is a not-for-profit association with 70 local offices in Kentucky, New York, Ohio, Pennsylvania and West Virginia serving 2.7 million members. News releases are available at news.eastcentral.aaa.com. Follow us on Twitter and Facebook.