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Drowsy Driving Is Dangerous. Even More So for Teens.

For the youngest drivers, sleep deprivation piles on the risk.

Young person sitting in the driver's seat of a car with hands on the wheel and eyes closed
pascal malamas/iStock/Getty Images Plus

When school let out on June 1, 2015, 16-year-old George Sinclair was ready for a nap. A student at San Diego’s St. Augustine High School, he was exhausted after having stayed up most of the previous night studying for finals.

When he woke up, though, he wasn’t in his bed—he was still in the front seat of his pickup truck, where he’d narrowly missed being impaled by a fence post. Sinclair had nodded off while driving and rolled his truck off the road and into a wooden fence. Although the post had punched through the windshield and right through the steering wheel, Sinclair had shifted just enough as the truck slid so the post ended up under his armpit.

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Despite the striking details of Sinclair’s near miss, the circumstances that led to it were hardly unique.

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Drowsy driving is considered a factor in about 7 percent of all crashes and about 16.5 percent of all fatal crashes. Even more concerning: Fatal crashes are up sharply, according to recently released information by the National Highway Traffic Safety Administration. It’s hard to pin down the exact number, given that state databases don’t list drowsy driving crashes in a separate category. The designation is also a subjective one: There’s no Breathalyzer equivalent that can be administered on site the way there is for drunk driving. Instead, it’s up to motorists, their passengers, or other observers to report that the driver was tired and/or fell asleep—feedback that can’t always be obtained, especially in the case of fatalities.

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Nevertheless, in a study released in 2018, video footage of more than 3,500 drivers showed the number of crashes involving drowsiness was close to 10 percent. For that study, footage had been gathered over the course of several months using in-car video cameras. Researchers analyzed the footage from the three minutes preceding each crash—captured at a rate of 15 frames per second—so they could measure the proportion of time drivers had their eyes open vs. closed.

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“You can see it with your own eyes on the video,” says Brian Tefft, a senior researcher with the AAA Foundation for Traffic Safety and one of the study’s co-authors. “When someone’s falling asleep, you’ll see their eyelids slowly drooping. When we look at measures like that … we know that the overall proportion of crashes that involve moderate to severe fatigue or drowsiness is in the vicinity of 10 percent or more.”

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Tefft also analyzed data from the Department of Transportation and found that drivers who’d gotten only five or six hours of sleep were more prone to what he called the “simple lapses in attention” all drivers make periodically, such as failing to notice a traffic signal, or misjudging how much time it takes to clear an intersection. “They made the same kinds of mistakes that we all make from time to time,” Tefft says, “but they made them more often.”

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More severe than lapses in attention are “microsleeps,” which may last for less than a second but can have serious ramifications. Not only is the vehicle still moving, but “a lot can change in the traffic environment,” Tefft points out. Plus, there’s an additional time lag while the driver reorients to the situation, further slowing response time. And then there’s outright falling asleep, which means (obviously) the driver simply isn’t responding at all. “For all intents and purposes,” Tefft says, “you’ve relinquished control of the vehicle.”

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Unsurprisingly, when he analyzed the DOT crash data, Tefft found that the drivers who’d slept less than four hours and then caused a crash were the most likely to report having fallen asleep. Severely sleep-impaired drivers were also more likely to have lost control of the vehicle or shown signs of overcompensating (for example, oversteering to try to correct drifting out of their lane), which could suggest they’d had a microsleep and were trying to recover from it.

When it comes to teens, driving is already risky enough even before layering in lack of sleep. They’re more likely to crash than drivers in all other age groups, and that risk is highest during the first month after they obtain a license. And if that doesn’t provide pause, this will: In 2020, vehicle crashes were the leading cause of unintentional injury death for 15-to-24-year-olds.

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First, teen drivers simply aren’t as experienced as more seasoned drivers. Most states only require about 50 hours of supervised driving before getting a license, which is still a far different scenario than when a teen actually gets behind the wheel without an adult co-pilot. And some states don’t require any supervised driving hours at all.

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As new drivers, teens aren’t yet adept at recognizing various situations and knowing how to respond quickly and appropriately, whether it’s gauging the amount of time to get through an intersection once the light turns yellow, or deciding whether they should brake or swerve to avoid hitting a squirrel.

They’re also likely to be distracted while driving. According to data released by AAA in 2020, more than a third of teen drivers said they’d texted while driving at least once in the past 30 days. Nearly as many confessed to running a red light at least once during the same time frame. And teens are also less likely to use seat belts, as drivers or as passengers. These behaviors exemplify what’s known about teens’ judgment (which is often lacking) and their penchant for risk-taking—both hallmarks of the teen brain.

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The brain remodeling that takes place during the teen years means impulsivity and reward-seeking have already revved up, while executive functioning lags behind. Teen drivers are functioning without the benefit of a mature prefrontal cortex and are making decisions accordingly, all while behind the wheel of a fast-moving vehicle that weighs 3,000 pounds or more.

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Fortunately, every state now has graduated driver licensing requirements in place which help counter the risks posed by teen drivers. The specifics vary, but most states require a set number of hours of supervised driving before getting a license and also place restrictions on underage passengers and late-night driving. Teens are issued a restricted license specifying these conditions and generally can’t apply for an unrestricted license until they turn 18.

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The good news: Graduated licensing requirements have been effective in reducing teen crashes since the mid-1990s, when they first began to be broadly implemented. As Tefft explains, driving at night “tends to be more dangerous than driving during the day for anybody, regardless of age, but especially so for teens.”

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Although compliance with teen nighttime driving restrictions is “far from perfect,” he acknowledges, the laws have had a dramatic influence simply by reducing the number of teen drivers on the road during the highest-risk time frame. Still, there’s only so much they can do to curtail dangerous teen behavior: One 2013 study found that more than a fourth of respondents said they’d changed their clothes or shoes while driving. Some even said they’d applied makeup or done homework.

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So, what happens when these same teens are operating a vehicle while they’re running on fumes?

Nothing good, obviously. Teen brains already don’t process information at optimal speed, and when they’re sleep-deprived, this declines even further. For teens, lack of sleep “really interacts with lack of experience,” Tefft says. “It’s going to be all the worse for a young person whose driving skills aren’t quite there yet, who’s less familiar with some of the hazards they may face on the road and whose responses to those hazards haven’t become quite as automatic as more experienced drivers’.”

Researchers have also shown that as teens’ sleep declines, their risky driving behaviors increase, whether it’s sending texts or emails, or driving without wearing a seatbelt (which was three times as likely for teens who’d slept less than six hours, compared with those who’d slept at least eight hours, according to a 2018 research letter published in JAMA Pediatrics).

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Sleep-deprived teens also react more impulsively to perceived threats and become angry more quickly. Neither bodes well when teens are faced with an aggressive driver, such as someone who tries to cut in front of them.

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In the wake of the success of graduated driver licensing requirements, Tefft and other experts view later school start times as the next major policy change that can make a real difference in reducing teen crashes.

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Robert Foss, director emeritus of the Center for the Study of Young Drivers at the University of North Carolina at Chapel Hill, has spent the bulk of his career focused on driver safety and teen drivers in particular. He notes the causal effect between changing school start times and teen crashes, with the bulk of the reduction taking place in the afternoon.

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“Basically, you shrink the amount of time teens are out there driving, and less driving equates to fewer crashes,” Foss says. “When you’re trying to reduce crashes … you need policies that apply to large groups of people and have the potential to alter their behavior in a beneficial way.”

He views later school start times as exactly that type of policy. “Change the [start] time,” he says, “and you’re going to reduce crashes.”

Policy changes aside, far too many drivers are still getting behind the wheel even when they know better. According to a AAA Foundation for Traffic Safety report released in 2020, 24 percent of respondents said they’d driven at least once in the past 30 days “while being so tired that they had a hard time keeping their eyes open.”

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If you’re that tired, you should pull over for a rest or a brief nap, says Kathi Wright, a Tennessee-based advocate for teen driver safety. In 2002, her 17-year-old nephew, Kyle Kiihnl, was walking on the sidewalk near his home when a truck jumped the curb and plowed into him. The driver, a fellow classmate at Germantown, Tennessee’s Houston High School, had fallen asleep at the wheel.

Kiihnl died instantly.

The teen driver who killed Wright’s nephew hadn’t been drinking or using drugs, but he was out late on a weekend night—a known risk factor for teen crashes (which is why many states now restrict teen nighttime driving). It was 2 a.m., and the driver was returning home from a concert he’d attended with a church group. He was driving at a time when he normally would have been asleep in bed, Wright points out.

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Wright now travels around the state presenting to groups of teens about drowsy driving, working with the Tennessee Highway Safety Office and others. She started by calling up a local driving school and offering to present to the teens. “It was a little 15-minute talk, and I felt like they were totally blown away with what I had told them, like they had never heard anything [about it before],” she said.

“At the end, I always ask, ‘Has anyone had a friend or family member involved in a drowsy driving crash?’ and there are always hands.”

Excerpted from The Sleep-Deprived Teen: Why Our Teens Are So Tired, and How Parents and Schools Can Help Them Thrive, by Lisa L. Lewis, M.S., published by Mango Publishing Group.