More than 2 million people will fall asleep this week in the United States while driving their motor vehicle, writes Matthew Walker in Why We Sleep: Unlocking the Power of Sleep and Dreams.  

“Drowsy driving is as problematic as drunk driving,” he observes. “Drunk drivers are often late in braking, and late in making evasive maneuvers. But when you fall asleep, or have a microsleep, you stop reacting altogether. A person who experiences a microsleep or who has fallen asleep at the wheel does not brake at all, nor do they make any attempt to avoid the accident.”

Accidents involving fatigued drivers tend to be far more deadly than those caused by alcohol or drugs.  

“Said crassly,” Matthew writes, “when you fall asleep at the wheel of your car on a freeway, there is now a one-ton missile traveling 65 miler per hour, and no one is in control.”

Even more dangerous are drowsy truckers. Matthew notes that approximately 80 percent of truck drivers in the US are overweight, and 50 percent are clinically obese. “This places truck drivers at a far, far higher risk of a disorder called sleep apnea, commonly associated with heavy snoring, which causes chronic, severe sleep deprivation,” he writes. “As a result, these truck drivers are far more likely to be involved in a traffic accident. And when a truck driver loses his or her life in a drowsy-driving crash, they can take a number of lives with them.”

One terrible example occurred in Union County, Florida, in January of 2006 when an eighteen-wheeler collided with a car and school bus. Seven people died, including a 20-month-old infant. The truck driver and nine children in the bus sustained serious injuries.

“The trucker was a qualified and legally licensed driver. All toxicology tests performed on his blood were negative,” notes Matthew. “However, it later emerged that he had been awake for thirty-four hours straight and had fallen asleep at the wheel.”  

Drunk driving and drowsy driving are each deadly by themselves, but what happens when they are combined? “It is a relevant question, since most individuals are driving drunk in the early-morning hours rather than in the middle of the day, meaning that most drunk drivers are also sleep-deprived,” Matthew notes.

In one study, Australian researchers analyzed two groups of healthy adults: one group became intoxicated to the legal driving limit (.08 percent blood alcohol); the other was sleep-deprived for a single night. “Both groups performed the concentration test to assess attention performance, specifically the number of lapses. After being awake for nineteen hours, people who were sleep-deprived were as cognitively impaired as those who were legally drunk.”

Put another way: if we wake up at 7 a.m., stay awake all day, then go socializing with friends late into the night while remaining completely sober, at 2 a.m., we are as cognitively impaired in our ability to attend to the road and what is around us as a legally drunk driver. Study participants began a significant decline in performance after just fifteen hours of being awake (ten p.m. in the above scenario).

Matthew concludes this chapter with the following warning: “There are many things that I hope readers take away from this book. This is one of the most important: if you are drowsy while driving, please, please stop. It is lethal. . . Many of us think we can overcome drowsiness through sheer force of will, but sadly, this is not true.”


Reflection: When is the last time I drove deprived of sleep? Did I pull over to rest?

Action: Talk to a loved one about the experience and commit to take this issue seriously.

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