The Line Between a Safe Driver and a Dangerous One Is Just a Single Hour of Sleep

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Even without all the insomnia-inducing traps of modern life — the blue light of iPhone screens to mess with their circadian rhythms, or Netflix to lure them into a few hours of sleep procrastination, or an office coffee-machine dispensing unlimited afternoon caffeine — our hunter-gatherer ancestors likely didn’t fare any better in the sleep department than we do.

Our hunter-gatherer ancestors, though, also didn’t have to get in a car and drive themselves anywhere after a night of tossing and turning. According to a 2013 Gallup poll, the average American gets roughly 6.8 hours of sleep each night, and around 40 percent get six hours or less — which puts them awfully close to the point where it becomes dangerous to get behind the wheel.

As Allison Aubrey reported this week for NPR, a new report from the AAA Foundation for Traffic Safety found that drivers who hit the road with six hours of sleep have twice as much risk of getting into an accident as drivers who slept for at least seven hours. And for those trying to get by on just four or five hours, the risk is four times as high — “close to what’s seen among drunken drivers,” Aubrey noted. According to one study, staying awake for 18 hours straight can cause the same cognitive impairment as a blood alcohol level of 0.05; at 24 hours, it’s closer to a blood alcohol level of 0.1, more than the legal limit for driving.

“If you have not slept seven or more hours in a given 24-hour period, you really shouldn’t be behind the wheel of a car,” Jake Nelson, AAA’s director of traffic safety advocacy and research, told NPR.

And yet despite the danger it poses, drowsy driving doesn’t carry nearly the same stigma as driving drunk. In part, that may be because fatigue is harder to quantify than intoxication — there’s no Breathalyzer for exhaustion. But for both the drunk and the drowsy, the key to getting behind the wheel is just giving yourself time — in one case, time to sober up; in the other, time to power down. “Taking a 10-to-20 minute nap every couple of hours on a long drive has huge safety benefits in terms of your ability to drive without crashing,” Nelson said — not as good as a full eight hours, but definitely better than taking your chances on the road.

A Single Hour of Sleep Separates Safe and Dangerous Drivers