Drowsy Driving: Statistics, Causes, and Prevention

This guide takes a deeper look at the prevalence and risks associated with driving while fatigued.

Last updated: Jul 26th, 2023
Drowsy Driving

Drowsy driving is a highly prevalent issue that poses considerable risk to drivers in the U.S. and elsewhere. The consequences of this issue should not be taken lightly. Even one impaired driver on the road can create a dangerous situation for everyone. These dangers, though, are mostly avoidable, as there are a number of ways to prevent unsafe driving conditions due to fatigue.

Understanding the impact of sleep deprivation is also important since it’s the primary cause of drowsy driving. In theory, the impairment caused by fatigue is comparable to the effects of consuming alcohol. But drowsy driving can also be influenced by certain medications, irregular work hours, and untreated sleep disorders. This guide outlines the prevalence and dangers associated with drowsy driving, as well as tips for detecting and avoiding it.

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What is drowsy driving?

Drowsy driving means operating a vehicle while sleepy or fatigued, typically to an unsafe degree. In this state, your alertness and focus are impaired, your reaction time is reduced, and your decision-making abilities are diminished. All this leads to a significantly increased likelihood of being in an accident. Common signs of drowsy driving include blinking more or longer than usual, struggling to keep your eyes open, frequent yawning, having difficulty concentrating on the road, letting your car drift, and ultimately falling asleep at the wheel.

Drowsy driving is impaired driving, and it’s crucial to understand any contributory factors and adopt proactive measures to avoid an accident. Adequate sleep, first and foremost, cannot be overlooked. Driving with only 4 to 5 hours of sleep significantly increases your risk of an accident — to a degree comparable with having a blood alcohol level above the legal driving limit.

What causes drowsy driving?

While the primary issue leading to drowsy driving is inadequate sleep, there are a number of other factors (most of which relate directly or indirectly to sleep):

  • Working extended or irregular hours (e.g., overtime or night shifts)
  • Drinking alcohol before driving or just before bed
  • Consuming caffeine too close to bedtime
  • Insomnia, obstructive sleep apnea (OSA), or other untreated sleep disorders
  • Not prioritizing quality sleep

To resolve these issues and take steps toward getting the recommended 7 to 9 hours of sleep per night, you will likely need to make changes to your lifestyle, daily schedule, and habits. If making these changes feels burdensome or gets overwhelming, it’s probably a good idea to talk to your doctor. Getting the proper amount of quality sleep is not only the best way to avoid drowsy driving but also vital to your health.

Sleep disorders

Drivers with untreated sleep disorders also have an elevated risk of drowsy driving. Common sleep disorders that lead to increased daytime fatigue include insomnia, OSA, and narcolepsy; OSA alone affects more than 12 million people in the U.S.


Many over-the-counter and prescription medications can induce fatigue, but the majority of these come with warning labels that indicate drowsiness as a side effect. Some examples of these medications include:

  • Sleeping pills
  • Narcotic pain pills
  • Some antidepressants
  • Tranquilizers
  • Some blood-pressure medications
  • Most cold or cough medicines
  • Some antihistamines
  • Muscle relaxants

Be sure to exercise caution when taking any of these medications; they can inhibit the abilities of even an experienced, well-rested driver.


Consuming alcohol typically induces sleepiness and impairs reaction time, amplifying the risk of an accident. The combination of fatigue and alcohol diminishes mental and physical alertness, leading to significantly impaired driving abilities. In one study, it was found that individuals who had only four hours of sleep experienced the same level of impairment after consuming a single beer as those who were well-rested did after consuming six beers.

Who is affected by drowsy driving?

According to a 2009–2010 survey conducted by the CDC, each year in the U.S., drowsy driving contributes to as many as 7,500 fatal motor vehicle accidents. In the same survey, adult respondents who reported habitually snoring, regularly falling asleep during the day, or sleeping less than or equal to six hours per night were also more likely to fall asleep while driving, compared to those who had none of these issues.

More recently, the CDC analyzed a 2011–2012 Behavioral Risk Factor Surveillance System (BRFSS) survey regarding drowsy driving and found that among the 92,102 respondents, 4.0% reported falling asleep while driving during the previous 30 days — that’s nearly 3,700 drivers.

Drowsy driving is a concern for people of every race, ethnicity, sex, age, income, education level, and employment demographic. Some of these groups include higher numbers of drowsy drivers, but the increased risk of an accident associated with driving while fatigued should be of equal concern to everyone. Individuals most likely to be involved in an accident related to drowsy driving include:

  • Younger drivers
  • People with untreated sleep disorders
  • Shift workers
  • Public safety personnel (e.g., paramedics and emergency medical technicians)

Among all age groups, drivers under 24 years of age are the most likely to fall asleep at the wheel. Drowsy driving accidents were also found to be more common among those on the road during late-night hours, the early pre-dawn period, and mid-afternoon.

How is drowsy driving detected and prevented?

Quickly recognizing drowsy driving — in yourself as well as others — can be crucial for ensuring a safe driving experience. The most common signs of drowsy driving are:

  • Frequent yawning, blinking, or difficulty keeping your eyes open
  • Difficulty keeping your head up (i.e., “nodding off” or “head bobbing”)
  • Forgetting the previous few miles or minutes of driving
  • Missing posted road signs, turns, or exits
  • Difficulty maintaining your desired speed
  • Drifting or weaving outside of your lane
  • Inconsistent speed

It’s also important to remember that these signs are not exclusive to drowsy driving and could potentially be the result of other unknown factors. However, if you observe multiple signs that might indicate impairment in a driver, you should maintain a safe distance and consider reporting the situation to the police. And if you begin to notice any of these signs in yourself, get off the road as quickly and safely as possible.

Avoiding drowsy driving

While consuming coffee or energy drinks may provide a temporary boost, relying solely on them is typically not a good idea. These beverages may create a sense of alertness, but their effects are fleeting, and you might not be as alert as you think. If you’re severely sleep-deprived, even if you consume high doses of caffeine, you may still experience “microsleep” episodes, or a few seconds of unconsciousness.

To ward off drowsiness while you’re driving, a better idea would be to consume a caffeinated beverage and promptly pull over — ideally to a safe location, such as a well-lit designated rest stop — and take a short nap. Scientific research has indicated that combining caffeine consumption with a short nap (15–20 minutes) can enhance alertness, but only for a short amount of time.

Long-term drowsy driving solutions include:

  • Getting regular quality sleep
  • Avoiding any alcohol before driving or medications that could cause drowsiness
  • Avoiding peak drowsy driving periods
  • Incorporate rest stops into longer commutes or when needed

By prioritizing sleep, avoiding substances that may cause drowsiness, and putting thought into your trips, you can greatly mitigate the risks associated with drowsy driving. That said, if you are regularly fatigued during the day or constantly struggle to stay awake while driving, you should consider consulting a doctor to confirm or rule out any underlying sleep disorders.


Drowsy driving poses a significant threat to road safety, but it is a problem that can be effectively addressed and mitigated. Seeking medical assistance for persistent daytime sleepiness or signs of sleep disorders can play a crucial role in ensuring alertness while operating a vehicle. By committing to being well-rested, alert, and responsible drivers, we can greatly contribute to the safety and well-being of everyone on the road. Raising awareness about the dangers of drowsy driving can significantly reduce the likelihood of accidents and ultimately save lives.



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  1. National Safety Council. (2019). Drowsy Driving Is Impaired Driving. nsc.org.

  2. UCLA Health System. (n.d.). Drowsy Driving. uclahealth.org.

  3. Wheaton, A. G., Shults, R. A., Chapman, D. P., Ford, E. S., & Croft, J. B. (2014). Drowsy Driving and Risk Behaviors — 10 States and Puerto Rico, 2011–2012. cdc.gov.

  4. National Highway Traffic Safety Administration. (2016). NHTSA Drowsy Driving Research and Program Plan. nhtsa.gov.

  5. National Safety Council. (2023). Fatigued Driving. nsc.org.

  6. National Highway Traffic Safety Administration. (n.d.). Drowsy Driving. nhtsa.gov.