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The Devastating Impact of Driving While Fatigued

Man fatigued and tired while driving

Drowsy driving is an official term. According to the Centers for Disease Control and Prevention (CDC), it is defined as driving a motor vehicle when you’re sleepy or fatigued. Although it may not sound so scary, drowsy driving a major problem in the U.S.

As early as 1972, the National Transportation Safety Board issued a recommendation concerning rest for airline pilots. In 1990, recommendations in regards to operator fatigue were first added to the Safety Board’s “Most Wanted List” of safety improvements.

In 2002, the National Sleep Foundation held a summit to prevent drowsy driving. In 2014, the National Transportation Safety Board held a one-day forum in Washington, D.C. to identify and address the dangers of drowsy driving. Drowsy driving is a major issue that lawmakers and government officials are trying to fix.

According to the UCLA Sleep Disorders Center, drowsy driving can be just as dangerous as driving under the influence of drugs or alcohol. It seems obvious that actually falling asleep at the wheel is hazardous. However, the danger begins before your eyes close.

Driving involves a number of specific cognitive processes. According to researchers, driving while drowsy can result in poor decision making and slowed reaction times. It can put you and others in danger.

Ten percent of drivers have fallen asleep while driving within the past year. More than 16 percent of deadly traffic accidents are caused by driver fatigue.

To put that in more relatable numbers, the National Highway Traffic and Safety Administration (NHTSA) says that there are more than 55,000 collisions each year resulting in about 40,000 injuries and 1,500 deaths. However, the NHTSA believes that these statistics are grossly underreported.

What Causes Drowsiness?

Tiredness can be caused by several factors, including the following.

Lack of sleep

You hold your breath for long enough, you will pass out, and your body will begin to take in oxygen again. If you don’t sleep, your body will eventually find a way to get it no matter what you’re doing at the time.

Your body clock

Your circadian rhythm affects your sleepiness. You’re supposed to get tired at night and be alert during the day.

If you stay up later than usual, your body may start to get sleepy at your regular bedtime. However, you can combat the drowsiness with caffeine, exercise and other types of stimulation.

You may be able to push past the fatigue and stay up until the wee hours of the morning. According to Why Am I Always Tired?.org, however, this can upset your natural circadian rhythm.

Once your circadian rhythm is disrupted, no amount of coffee can fix it. In fact, caffeine, stimulants and other stressors can lead to further adrenal fatigue. This can put you in an endless cycle of drowsiness.

Sleep Debt

Everyone has different sleep requirements. However, the amount of sleep you need is generally consistent. If you need 7 hours of sleep a day and you only get 5, you create a sleep debt.

The sleep debt adds up over time. The more sleep you miss, the more sleep your body will need to catch up. 

The UCLA Sleep Center also explained that sleep surveys consistently find that many adults are not getting adequate sleep. They don’t feel rested and may get drowsy every time they operate a motor vehicle.

Sleep Disorders

According to, 70 million people are sleep deprived or have a sleep disorder. The NHTSA urges health care professionals to become more informed about sleep problems and drowsy driving.

The NHTSA suggests that health care providers talk to patients about getting enough sleep, which is the primary way to prevent drowsy driving. Recognizing and treating medical conditions that cause fatigue can also help.

You May Not Notice You’re Drowsy Until It’s Too Late

Drowsiness can sneak up on you. It may also be such a part of your daily life that you don’t realize how fatigued you are.

When you’re feeling sleepy, you may not realize how much your drowsiness is limiting your alertness. You might even think that you can fight through the sleepiness.

However, you might be closer to causing a crash than you think. In a survey conducted by the Insurance Corporation of British Columbia (ICBC), 30 percent of respondents said that they have actually fallen asleep behind the wheel. Still, only about half of the respondents said that they thought drowsy driving is a serious safety issue.

Some signs of drowsiness include:

  • Being oblivious to vehicles behind you and being surprised when they pass you
  • Realizing that you have no recall of the past few miles that you’ve driven
  • Daydreaming or excessive yawning
  • Maintaining an inconsistent driving speed
  • Wandering sideways in your lane
  • Restlessness, irritability or aggressiveness
  • Poor judgement
  • Having trouble keeping your eyes open or your head up

If you’re driving along a high-speed road and hit a rumble strip, it means that you’re distracted. The purpose of the strips is to alarm drivers who are drifting off the road because of fatigue. If you are alerted because you’ve rolled across one, it probably means that you should stop driving and get some rest.

Crashes Caused By Drowsy Driving

The estimated number of car crashes caused by drowsy driving used to lie somewhere around 2 or 3 percent. However, in 2013 the Insurance Journal reported that a Virginia Tech Transportation Institute found that number to be more accurate at 20 percent.

This naturalistic study found that 20 percent of drivers who crashed showed signs of drowsiness before the accident. Drivers showed signs of drowsiness in 16 percent of all near crashes. 

In 2003, New Jersey enacted Maggie’s Law. This legislation makes it illegal to drive when you know that you haven’t had enough sleep. Drivers who are operating a motor vehicle after being awake for more than 24 hours can be charged with vehicular homicide.

The law was a response to a crash that occurred in 1997, when a driver who had been awake for 30 hours crossed into oncoming traffic and hit Maggie McDonald’s car head on. Maggie was killed, but the judge didn’t let the jury consider the driver’s sleep deprivation because there was no law against falling asleep while driving.

A New York Times report states that a bus accident that killed 15 passengers in 2011 happened after the driver admittedly had gotten no sleep for three days before the wreck. Passengers reported that the bus was speeding and veered off the road with no attempt at braking.

The Yale Daily News reported that in 2017 a Yale shuttle bus hit a parked SUV during rush-hour traffic. The shuttle driver was coming to the end of a shift and may have been suffering from fatigue.

Driver fatigue has been blamed for the crash that killed writer and comedian James McNair and seriously injured comedian Tracey Morgan, according to CBS News. The Wal-Mart truck driver responsible for the accident hadn’t slept for at least 28 hours before crashing into the back of their vehicle.

A contributor to U.S. News and World Report was rear-ended by a driver while she was on her way to pick up her children. The driver admitted to having fallen asleep at the wheel. He had a child in the car with him. The results of the incident could have been worse.

What Time Do Most Crashes Caused By Driver Fatigue Happen?

The New York State Department of Health says that drivers are more likely to feel fatigued from 1 p.m. to 4 p.m. and from 2 a.m. to 6 a.m. This is due to your circadian rhythm. If you have a regular sleep schedule, you’re used to being asleep from 2 a.m. to 6 a.m. Your circadian rhythm also makes you feel sleepy in the late afternoon.

Who Is At The Greatest Risk Of Driving While Fatigued?

The following categories of people are more likely to drive while drowsy:

  • People who snore or sleep less than 6 hours a day, according to a CDC Morbidity and Mortality Weekly Report
  • Commercial drivers
  • Shift workers who take long, late or overnight shifts
  • Drivers with untreated sleep disorders
  • People who use certain medications
  • Adolescent drivers who sleep less than 8 hours a night, according to Teen Driver Source
  • Young, male drivers, according to the UCLA Sleep Center
  • Business travelers
  • Drivers who have been consuming alcohol
  • Drivers who have been on the road for longer periods of time

What Are The Characteristics Of Fatigue-Related Crashes?

According to a National Center on Sleep Disorders Research (NCSDR) and NHTSA expert panel, it is difficult to test a driver for fatigue. Unlike with drugs and alcohol, there is no measurable assessment to quantify levels of drowsiness. However, a characteristic fatigue-related crash has the following features:

  • The driver is alone
  • The crash involves a single vehicle
  • The incident involves veering out of the driving lane
  • The driver doesn’t try to prevent the collision
  • The collision happens on a highway
  • The crash occurs during peak fatigue times

How Can You Prevent Drowsy Driving?

Take Turns

The ICBC study mentioned above found that men are more likely than women to do all of the driving on long road trips. Even if you love to drive, let your partner take over for a while. Switching drivers every couple of hours is one of the best ways to prevent driver fatigue. cited a study conducted by researchers at National Central University in Taiwan. The researchers found that even just an hour and 20 minutes of driving can make it unsafe for a driver to continue.

Take A Nap

The only remedy for drowsiness is sleep. No amount of caffeine is going to repair your reaction time and cognitive alertness. If you’re experiencing signs of drowsy driving or just feel tired, pull over and take a power nap.

Even a short 10-minute nap can restore your alertness and focus, but 45 minutes is ideal. However, the Federal Motor Carrier Safety Administration warns that you should wait at least 15 minutes after waking before you start to drive. It’s also more effective for improving driver alertness to take a nap before you feel tired than to take one after you realize that you’re drowsy.

Drive During the Day

If you drive when you’d normally be getting sleepy, you’re going to get sleepy. Trying to drive through the night to avoid traffic is guaranteed to turn you into a drowsy driver. If you have to take a trip that’s longer than daylight hours, consider stopping somewhere overnight.

Avoid Alcohol When Driving

You know that you’re not supposed to drink enough alcohol to put you over the legal limit before driving a car. However, even alcohol consumption that keeps you below the legal limit can lead to drowsy driving.

Research shows that minimal alcohol consumption added to partial sleep deprivation can increase your crash risk. In the study, participants who had a blood alcohol level of .037 when beginning to operate a driving simulator experienced steering deviations and delayed reaction times.

Make Sure Your Adolescent Gets Enough Sleep

Teen Driver Source says that teenagers begin to get less sleep from the ages of 13 to 19. Because they’re new to sleep deprivation, they may not adjust to it as easily as adults.

They’re also new to driving. The combination can be lethal. Teens should get at least 9 hours of sleep a night to be as alert as they need to be to prevent driver fatigue.

Dos and Don’ts To Prevent Driving While Fatigued


  • Get enough sleep
  • Avoid medications that may impair your driving
  • Avoid driving after consuming alcohol
  • Recognize the signs of driver fatigue
  • Maintain a healthy lifestyle


  • Rely on caffeine to keep you awake
  • Depend on tricks, such as opening the window or turning up the radio, to keep you awake
  • Think you can push through sleepiness

The Bottom Line

Just because you lie in bed for 8 hours a night doesn’t mean that you’re getting adequate sleep. Fragmented sleep can be caused by illness, sleep disorders, outside disturbances, job-related duties or children. The NHTSA reports that the National Transportation Safety Board has found that fragmented sleep patterns are one of the primary predictors of collisions related to driver fatigue.

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