Drowsy Driving


Busy lives and other causes lead many Americans to operate with a sleep deficit (1). Adults typically need seven to nine hours (2) of sleep per night, but research suggests that approximately one-third (3) fall short of this goal. Short sleep may cause altered emotions and reduced concentration and performance (4) that can be dangerous when driving.

Drowsy driving occurs when someone who is sleepy or fatigued attempts to operate a motor vehicle. Understanding the dangers, causes, and techniques to prevent drowsy driving can help combat this public health risk.

How Common Is Drowsy Driving?

Drowsy driving is likely quite common, but the extent of the problem is unclear due to difficulties identifying incidents.

While 97% of drivers disapprove of drowsy driving (5), 24% say they have struggled to stay awake while driving within the last 30 days.

On an annual basis, drowsy driving is thought to be a factor in approximately 2.3% to 2.5% of fatal crashes (6) and around 5 to 6 million crashes that lead to injury or property damage. The National Highway Traffic Safety Administration reports that in 2019 alone, 697 fatalities (7) involved a drowsy driver. However, this number could be far greater since there is not always conclusive evidence that drowsy driving was at play. Some research suggests that observable driver drowsiness is actually present in closer to 8.8% to 9.5% of crashes (8).

Why Is Driving While Drowsy Dangerous?

Accidents are the main danger of drowsy driving. Sleep deprivation affects a host of factors that influence driving ability.

Sleep deprivation can impact cognition and attention (9) as well as decision-making skills (10), impairing a driver’s ability to stay focused on the road and make good decisions quickly. The effects of sleep deprivation are often compared to drunkenness, but some research hints that drowsiness could have an even more significant impact on driving. In one study, sleep-deprived participants had slower reaction times (11) than those who had consumed the legal limit of alcohol, and drinking coffee did not mitigate the effect.

When a driver is tired, they may also be more likely to experience microsleep (12). Microsleep is a brief sleep episode that lasts for .5 to 15 seconds. Because these periods are so brief, an individual may be unaware that they have slept at all. However, those valuable seconds can be critical when driving. If you are traveling at 70 miles per hour, you cover 510 yards in 15 seconds, which is ample opportunity for an accident.

Risk Factors of Drowsy Driving

The obvious causes of drowsy driving are sleep deprivation and excessive daytime sleepiness. However, certain risk factors can increase the likelihood of these conditions:

  • Shift Work: Shift work (13) that falls outside of traditional working hours often interferes with sleep, leading to the excessive sleepiness and impaired vigilance that are hallmarks of drowsy driving.
  • Long-Haul Driving: Long-haul drivers may break up sleep periods instead of sleeping throughout the night. Even if they obtain the recommended number of sleep hours, this irregular sleep schedule (14) may disrupt the sleep drive over time.
  • Sleep Disorders: Obstructive sleep apnea (15) and other sleep disorders (16) can contribute to daytime tiredness and increase the likelihood of drowsy driving.
  • Medications: Many over-the-counter and prescription medications (17) can cause sleepiness and impair driving. Even if the user does not feel tired, their response times may be slower. Common medications that may affect driving include antidepressants, allergy pills, cold medicine, and opioid pain relievers.
  • Alcohol Consumption: Drunk driving is a major hazard to personal safety and public health. Even if a driver is not under the influence while operating the vehicle, regular drinking may be linked to increased daytime sleepiness (18).
  • Time of Day: Because of variations in the body’s intrinsic sleep-wake cycle, drowsy driving accidents are most likely to occur between midnight and 6 a.m. or in the late afternoon (19).
  • Age: Many teenagers experience chronic sleep loss (20) due to caffeine consumption, electronic use, and a biological clock at odds with academic schedules, which may increase the rate of drowsy driving accidents for this age group.

Signs You May Be Too Tired to Drive

If you know that you are exhausted or have not been sleeping well, that is a clear signal that you should not get behind the wheel. However, some indications of insufficient sleep are not as obvious. The American Academy of Sleep Medicine recommends drivers be on the lookout for the following warning signs that they may be too tired to drive:

  • Yawning
  • Heavy eyelids
  • Nodding off
  • Difficulty remembering the last few minutes
  • Trouble driving at a constant speed
  • Drifting between lanes
  • Missing your turn or road signs

Tips for Avoiding Drowsy Driving

Drowsy driving is dangerous, but the good news is that it can be avoided. The following tips can help:

  • Get More Sleep: Getting enough quality sleep is the best way to feel rested and alert and avoid falling asleep while driving. Allowing extra time for rest and following smart sleep hygiene practices can make a big difference.
  • Avoid Alcohol Consumption: Alcohol can reduce sleep quality (21), potentially leading to more daytime sleepiness.
  • Be Aware of Medication Side Effects: Avoid driving while taking medication that can interfere with alertness, and consult with your doctor for strategies to minimize driving risks.
  • Treat Underlying Sleep Disorders: Addressing sleep disorders with a medical professional may improve your rest and reduce daytime tiredness.
  • Schedule Your Trip Wisely: If possible, avoid driving between midnight and 6 a.m. and in the late afternoon, when most people tend to be more tired. You may also want to take breaks every few hours, or switch driving duties with another person.
  • Change Your Plans as Necessary: If you realize that you are too tired to drive, change your plans. You might consider using public transportation, asking a friend to drive, or delaying your travel.
  • Take a Power Nap: If you notice signs of sleepiness while en-route and start wondering how to stay awake while driving, find a safe place to pull over and take a 20-minute nap before resuming travel. This may give you a short burst of alertness until you reach your destination.


+ 21 Sources
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  3. 3. Accessed on August 21, 2021. https://pubmed.ncbi.nlm.nih.gov/26890214/
  4. 4. Accessed on August 21, 2021. https://www.ncbi.nlm.nih.gov/books/NBK19961/
  5. 5. Accessed on August 21, 2021. https://aaafoundation.org/2019-traffic-safety-culture-index/
  6. 6. Accessed on August 21, 2021. https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812446
  7. 7. Accessed on August 21, 2021. https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813060
  8. 8. Accessed on August 21, 2021. https://aaafoundation.org/prevalence-drowsy-driving-crashes-estimates-large-scale-naturalistic-driving-study/
  9. 9. Accessed on August 21, 2021. https://pubmed.ncbi.nlm.nih.gov/21075236/
  10. 10. Accessed on August 21, 2021. https://pubmed.ncbi.nlm.nih.gov/26414989/
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  16. 16. Accessed on August 21, 2021. https://pubmed.ncbi.nlm.nih.gov/32809555/
  17. 17. Accessed on August 21, 2021. https://www.fda.gov/consumers/consumer-updates/some-medicines-and-driving-dont-mix
  18. 18. Accessed on August 21, 2021. https://pubmed.ncbi.nlm.nih.gov/31263899/
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