The Science of Sleepy Driving

sleepy driving

The Big Deal About Feeling Sleepy

For many of us, our days are about fitting in as much as we can from the time we wake up until we go to bed at night. From dealing with hectic work schedules to juggling busy family lives to having 24/7 access to technology and entertainment, sleep often falls to the bottom of the priority list.

That's why for a lot of people, feeling "sleepy" has become just another part of life and not that big of a deal. But did you know that investigators found that sleep deprivation was a major factor in a few major disasters, including the 1979 nuclear accident at Three Mile Island and also in the nuclear meltdown at Chernobyl? It's also been discovered that sleep deprivation played a role in the grounding of the Exxon Valdez oil tanker and the explosion of the space shuttle Challenger.

While the vast majority of us will never be in command of a space shuttle or oil tanker, most of us will get behind the wheel of a car during our lifetime. And statistics tell us that many of us will do this while deprived of sleep.

Sleepy Driving by the Numbers

According to the National Sleep Foundation, 60% of adult drivers, or about 168 million people, say they have driven while drowsy in the past year. More than one-third of people have actually fallen asleep behind the wheel.

sleepy driving statistics

The National Highway Traffic Safety Administration estimates that every year, 100,000 police-reported car accidents are the result of driver sleepiness. In reality, this number is likely higher, as it is difficult to link crashes to fatigue. Here are some other sleepy driving statistics:

  • The Institute of Medicine estimates that drowsy driving is actually responsible for a full 20% of all motor vehicle accidents.
  • That would make drowsy driving a factor in 1 million crashes, 500,000 injuries, and 8,000 deaths in the United States each year.
  • About 15% of heavy truck accidents involve fatigue.
  • Approximately 12.5% of crashes that end in hospitalization are caused by fatigue.

How Much Sleep Do We Need?

The amount of sleep a person needs depends on several factors, including age. Teenagers require about nine hours of sleep a night on average, and adults should get about seven to eight hours of sleep. Too little sleep results in a "sleep debt," and eventually your body will start demanding that you make up that debt.

While some people may feel that they can function just fine with five or six (or less) hours of sleep, researchers have found that getting less than six hours of sleep a night translates to a bigger sleep debt than you may realize. Over a two-week span, that debt adds up to the equivalent of two full nights of missed sleep. If you average only four hours of sleep a night for a few weeks, your brain reacts as though you haven't slept at all for three nights in a row.

Almost one-third of American workers get less sleep than the recommended seven to nine hours. According to the Centers for Disease Control and Prevention, 30% of people say they get six or fewer hours of sleep a day. People who work night shifts or work more than 40 hours a week are particularly at risk for sleep deprivation.

Why exactly we sleep is still something that scientists are trying to pinpoint. They have developed several theories, however, and one of those theories is that sleep "restores" functions that are lost or become depleted while we are awake. Among the areas that are restored is cognitive function.

The Effects of Sleep Deprivation

Sleep deprivation negatively affects your ability to focus and to access higher-level cognitive functions. Scientists have found that after a period of missed sleep, there is a noticeable change in brain activity that corresponds to a lower level of alertness, concentration, working memory, and logical reasoning.

lack of sleep

When sleep deprived people were tested using a driving simulator, they performed as badly or worse than those who were intoxicated. Furthermore, a lack of sleep intensifies alcohol's effect on the body, so a tired person who drinks will become more impaired than someone who is well rested.

Researchers in Australia found that being awake for 24 hours created impairment equal to a blood alcohol concentration of 0.10%, higher than the legal driving limit. After 18 hours awake, a person is as impaired as if he or she were legally drunk.

What's most worrisome, scientists point out, is that many people are too tired to realize how sleep-deprived they are even though they are suffering from cognitive impairments that can put them – and others – at risk.

Signs You're Too Tired to Drive

The National Sleep Foundation identifies several signs that indicate you're too tired to drive. These include:

  • Difficulty focusing
  • Increased daydreams
  • Yawning or frequent blinking
  • Difficulty remembering the past few miles you've driven
  • Drifting out of your lane
  • Missing traffic signs
  • Hitting the rumble strip
  • Feeling irritable and/or restless
  • Heavy eyelids
  • Trouble keeping your head up

If you experience any of these signs of fatigue, you should pull over immediately to rest or change drivers. Opening windows and playing loud music aren't effective ways to stay alert.

Injured in a Car Accident?

From fatigue to distractions to dangerous weather conditions, there are many factors that can lead to a car accident. No matter how careful you are, there are other drivers on the road who may not take the same precautions. If you've been the victim of a car accident and have questions about your injuries and your legal rights, feel free to get in touch with us for a free legal consultation. We're available 24/7.

“Brain Basics: Understanding Sleep.” National Institute of Neurological Disorders and Stroke. July 24, 2015.
“Facts and Stats.” 2015.
“Stats About Drowsy Driving Prove Being Tired Behind the Wheel is More Serious Than You Think.” The Huffington Post. November 4, 2014.
“Why Sleep Matters.” December 18, 2007.