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You obviously know not to get behind the wheel when you’re intoxicated—but what about when you’re exhausted? Fatigue was the cause of 20 percent of all documented crashes in a recent study from the Virginia Tech Transportation Institute Center for Vulnerable Road User Safety.
Researchers recruited 100 drivers who commute into or out of the Northern Virginia/Washington D.C. area and equipped their cars with unobtrusive sensors and video cameras to study naturalistic driving behavior. They also collected 20,000 randomly selected 6-second video segments, which let them notice signs of sleepiness—including closed eyes, head bobbing, and even drivers falling asleep at the wheel.
The result: In 20 percent of all car crashes and 16 percent of all near crashes documented in the study, the driver showed signs of fatigue. While that number is definitely shocking, this was a relatively small study—so it’s unclear whether the stats hold up for the entire country. The latest data from the National Highway Traffic Safety Association (NHTSA) shows that only 2.5 percent of fatal crashes in 2010 were the result of drowsy driving, but that doesn’t tell the whole story, either, since it doesn’t account for fender benders or serious but non-fatal accidents. What we do know is that there were 750 fatal crashes due to drowsy driving in 2010 alone, and the recent study indicates that number of less-severe accidents may be even higher.
Unfortunately, there is no legal limit when it comes to sluggish driving, so you’ll have to monitor yourself for signs of extreme drowsiness. If you’re sleep deprived—whether it’s from not enough sleep or poor-quality sleep—you shouldn’t get behind the wheel, says sleep expert Michael Breus, MD. So how can you tell the difference between your usual morning grogginess and being too drowsy to drive? If you fell asleep in less than five minutes the night before, it’s a sure sign you’re deprived, says Breus. Other signs include having trouble focusing or misplacing objects like your phone or keys. If you want a quick litmus test, Breus suggests lying down and closing your eyes for 30 seconds before getting behind the wheel. If you feel like you could truly fall asleep and you have trouble getting up, you shouldn’t be driving.
If you’re already in the car, watch for warning signs like incessant yawning, frequent blinking, trouble keeping your eyes open and focused, and not being able to remember driving the last few miles, says Jose Ucles, from the Office of Communications and Consumer Information at the NHTSA. If you notice any of these cues or happen to hit the rumble strips on the side of the road, it’s definitely time to get off the road. “The results are staggering,” says Breus. “If you’re going 60 miles per hour and close your eyes, it takes just three seconds to go off the road. You really don’t have a lot of time to react.”
It’s also important to remember that if you’ve taken any sleep aids in the last 24 hours, they may still be in your system. And avoid all alcohol if you’re already groggy. Just one glass of wine can multiply the effects of sleep deprivation—even though you may be under the legal alcohol limit, says Breus.
So what if you are driving when you realize you shouldn’t be? The NHTSA suggests pulling over, drinking two cups of coffee, then taking a 15-20 minute nap so you get a little sleep before the caffeine takes effect. That said, sleeping in a parking lot or on the side of the road isn’t exactly the safest thing. If you can’t stop at a hotel, leave your car in a nearby parking lot and call a cab or take public transportation home. Worst-case scenario, stopping to grab two cups of coffee, then waiting 15-20 minutes for it to take effect before driving to the closest place where you can catch some Zzzz’s is your next best option.
The verdict: Drowsy driving may not be as dangerous as drunk driving, but it accounted for 750 fatal crashes in 2010. And without any true guidelines, it’s crucial to monitor yourself to make sure you’re alert enough to drive. If you’re unsure, opt to have someone else take the wheel.
More from Women’s Health:
9 Ways to Drive Safe
When Multitasking Can Be Deadly
Should I Drive With a Hands-Free Cell Phone?