A man sits in the driver's seat of a car at night.

There's no debate that driving while sleepy is dangerous and unacceptable. Yet almost a third of people in a recent AAA survey said at least once in the prior month they had driven while so tired that they could barely keep their eyes open.

Perhaps contributing to the problem: prescription sleep aids. One in 5 Americans who take those drugs said they had gotten behind the wheel within 7 hours after taking the medication, according to a 2018 nationally representative Consumer Reports survey of 1,767 U.S. adults. That's even though the directions on most sleep drugs advise that you not take them unless you can sleep for at least 7 or 8 hours afterward—to reduce the possibility of leftover grogginess.

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Drowsy driving is “almost impossible to avoid,” says Barbara Phillips, M.D., a recently retired professor at the University of Kentucky College of Medicine. In a country where few areas have comprehensive public transit systems, she says, sometimes people don’t have a choice: “Even the best-intentioned people get stuck drowsy driving sometimes.” 

Sleep deprivation can impair your driving as severely as alcohol can. According to the National Sleep Foundation, if you’ve been awake for 24 hours, that’s equivalent to having a blood alcohol content of .10 (.08 is considered legally drunk).

Though it can be difficult to precisely measure the frequency of drowsy driving accidents—because there’s no easy test for it, as there is for blood alcohol content—a 2018 AAA study, which analyzed video of drivers just before a crash, found that 9.5 percent of accidents were caused by sleepy drivers.

Here is what to know about drowsy driving and what can—and can’t—help you stay alert behind the wheel.

Before You Get Behind the Wheel

These steps can help ensure that you’re alert before you jump into the driver’s seat in the first place.

Get adequate sleep. At least 7 hours is what the average adult needs, according to the Centers for Disease Control and Prevention.

Know when to ask for your doctor’s help. If you’re getting enough hours of sleep but are still drowsy during the day, wake repeatedly at night, or your partner complains that you snore, ask your doctor whether you might need to be evaluated for a sleep disorder. Even with what looks like sufficient slumber, you could be at risk for nodding off while driving if you’re sleeping poorly or have a health condition that affects the quality of your sleep, says Raman Malhotra, M.D., associate professor of neurology at Washington University School of Medicine.

For instance, if you have obstructive sleep apnea, which is marked by numerous pauses in breathing each night, you might be more likely to feel tired at the wheel, even if you got 7 hours of sleep.

Take a look at your meds. Talk with your doctor about the medications you take regularly. Many prescription and over-the-counter drugs, including antihistamines, antidepressants, certain blood pressure medications, some anxiety drugs, muscle relaxers, and, of course, sleep medications—can make you drowsy. Some may interact with other meds to cause fatigue. Your doctor may be able to adjust your regimen—say, by changing the timing of certain doses—to decrease the likelihood that you’ll feel sleepy while driving.

Prep for long drives. Even if you’re properly rested, hours and hours on the road can lull you into sleepiness. If you’re taking a road trip, make sure to get a good night’s sleep ahead of your journey.

What May Help You Stay Alert

If you’re feeling a little fatigued but have to drive, consider the following:

Drive with a companion. Having someone who can take the wheel for a while so that you can nap is good common sense. And while you’re driving, your companion can keep up a conversation to keep you engaged—and tell you whether your driving is getting erratic.

Know when it’s time to take a break. Even the most alert drivers should take a break about every 2 hours, Malhotra says. And note that studies have shown that drowsy people are unlikely to notice that they’re driving poorly. So, pay close attention for these clues that you're driving while drowsy:

  • Droopy eyelids; blinking or yawning frequently

  • Drifting out of your lane or hitting a rumble strip on the side of the road

  • Realizing that you don’t remember the last few minutes or miles that you’ve been driving

  • Missing a road sign or exit

Get some shut-eye. If you notice any of the above, find a safe place to pull off the road and take a 15- to 20-minute nap in your car. Malhotra recommends waiting an additional 5 minutes after you wake up before hitting the road again, to give yourself a chance to become fully alert. (And keep that nap short—sleeping longer than 10 to 20 minutes can make you feel groggy and disoriented for up to a half-hour after you wake up, according to UpToDate, an online decision-making tool for healthcare professionals.)

Get some caffeine. If you can’t nap, or even if you can, a dose of caffeine will help keep you more awake and alert, at least for a few hours. To make sure you get enough caffeine to really perk you up—Phillips recommends about 150 mg—your best bet is coffee. 

An 8-ounce cup of brewed coffee contains 95 mg of caffeine, and 12 ounces has 142 mg. A can of Diet Coke has only 46 mg of caffeine, and an 8-ounce cup of brewed black tea has 47 mg.

If you turn to coffee as a wake-up tool, once you drink it wait at least 15 minutes to give the caffeine time to kick in before getting back behind the wheel, Phillips says.

Skip these two common tricks. Studies show that neither driving with the windows open to keep cold air blowing on your face nor turning the radio up loudly will keep you alert.

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