Drowsy Driving

Patient Information Brochure


How common is drowsy driving?

Drowsy driving is a serious public health concern, and a leading cause of motor vehicle crashes. Surveys indicate that in the past year as many as 60% of drivers report that they have driven drowsy, and 18% report having actually fallen asleep behind the wheel. Several studies agree that drowsy driving contributes to over 20% of road fatalities.

Drowsy driving crashes are more likely:

  • to occur at night or in the mid-afternoon (when sleepiness is naturally higher);
  • to occur on roads with higher speeds like highways;
  • to involve a single vehicle driving off the road;
  • and to result in serious injuries.

The driver is often alone and makes no effort to brake or to take other action to avoid the crash.

How dangerous is drowsy driving?

Driving while drowsy can be as dangerous as driving while drunk. Driving performance after being awake all night is as impaired as driving with a blood alcohol concentration (BAC) of 0.08g%, which is the “legal limit” in all Canadian provinces and territories.

Falling asleep while driving is clearly dangerous, but studies also show that drowsy drivers:

  • take longer to react;
  • are less attentive to the environment;
  • and have impaired decision making skills;
  • all of which make them dangerous on the road.

Who is at risk for drowsy driving crashes?

No driver is exempt from the risks associated with drowsy driving – including professional drivers. Several risk factors have been identified that increase the probability of drowsy driving crashes. These include:

Acute and chronic sleep deprivation

Failure to get enough sleep on a regular basis to feel alert during the day is perhaps the greatest risk factor for having a drowsy driving crash.

Young, male drivers

The group at greatest risk for drowsy driving crashes is between 16-24 years of age.

Long-distance driving

This factor is a major reason why commercial truck drivers are more likely to have sleepy driving accidents than other drivers.

Non-traditional work schedules (e.g., shift work)

Shift workers are likely at greater risk because they have high rates of daytime sleepiness.

Undiagnosed or untreated sleep disorders

Sleep disorders, such as insomnia, sleep apnea, and narcolepsy, interfere with sleep quality and quantity.

Alcohol, sleeping pills, and other sedative medications

Drinking even small amounts of alcohol when already tired or taking medications that cause sleepiness will significantly increase the chance of having a drowsy driving crash.

What are the signs that you are too drowsy to drive?

Sleepiness is the body’s way of telling you that you are in need of sleep, in much the same way that hunger signals your need for food. In healthy individuals, sleepiness can result from:

  • obtaining inadequate or poor quality sleep;
  • sleeping when the body wants to be awake (e.g., night shift workers); and
  • the time of day: people are likely to feel sleepy in the mid-afternoon and again in the early morning hours (i.e., 1:00 - 5:00 am) regardless of the quantity and quality of previous sleep.

Substances such as prescription medications, over-the-counter sleep aids, and alcohol can cause sleepiness. Sleepiness is also a major symptom of a number of sleep disorders, including sleep apnea and narcolepsy.

If you feel sleepy or experience the following sleepy symptoms or driving behaviours, you should stop and rest or let someone else take over driving.


Sleepy driving symptoms Sleepy driving behaviours
Head nodding “Zoning out” while driving (e.g., missing exits or turns)
Eyelids drooping, feeling heavy, or frequet blinking Drifting out of your lane
Frequent yawning Difficulty maintaining a constant speed
Not being able to remember what happened in the last few minutes. Hitting a rumble strip
Having wandering thoughts Frequently changing your position
  Increased reaction time


What should I do if I experience drowsy driving?

Research has shown that strategies used by many drivers when feeling drowsy, such as turning up the radio volume, rolling down the window, and turning up the air conditioner are not helpful. The following strategies ARE effective for reducing drowsy driving risk:

  • Prevent drowsy driving before it happens. Be sure to get adequate sleep the night before a long-distance trip so that you are well rested for the drive. The average adult needs 7 or more hours of sleep nightly.
  • Plan to drive at a time when your body feels more alert and take frequent breaks.
  • Whenever possible have an alert companion with you to share the driving duties.
  • Use effective sleepiness countermeasures. The best countermeasure to drowsy driving is to stop driving and rest until you no longer feel sleepy. Let an alert companion take over driving duties. Caffeine and napping may increase alertness for two or three hours while driving, but are not substitutes to obtaining adequate sleep.
  • Seek treatment for drowsy driving risk factors. If you think you may have a sleep disorder, consult your doctor. Effective treatment of sleep disorders reduces daytime sleepiness, improves physical and mental health, and reduces the risk of drowsy driving crashes.


Authored by:
J. Todd Arnedt, Ph.D.
Department of Psychiatry & Neurology, University of Michigan Medical School, Ann Arbor, MI, USA