FAQs: Drowsy Driving

February 15, 2005

Questions


 

Introduction

The National Highway Traffic Safety Administration (NHTSA) conservatively estimates that 100,000 police-reported crashes are the direct result of driver fatigue each year, resulting in an estimated 1,500 deaths, 71,000 injuries, and $12.5 billion in monetary losses.

Definitions of drowsy driving generally involve varying uses and definitions of fatigue, sleepiness, and exhaustion. For the purpose of the discussion at hand, drowsy driving is simply driving in a physical state in which the driver's alertness is appreciably lower than it would be if the driver were “well rested” and “fully awake.”

How serious of a problem is drowsy driving?

On the national level, the National Highway Traffic Safety Administration (NHTSA) conservatively estimates that 100,000 police-reported crashes are the direct result of driver fatigue each year, resulting in an estimated 1,500 deaths, 71,000 injuries, and $12.5 billion in monetary losses. However, it is very difficult to determine when fatigue causes or contributes to a traffic crash, and many experts believe these statistics understate the magnitude of the problem.

On the individual level, driving while tired is very dangerous, because a driver who falls asleep may crash head-on into another vehicle, a tree, or a wall, at full driving speed, without making any attempt to avoid the crash by steering or braking.

The inability of a sleeping driver to try to avoid crashing makes this type of crash especially severe. Some studies have found people's cognitive-psychomotor abilities to be as impaired after 24 hours without sleep as with a BAC of 0.10%, which is higher than the legal limit for DWI conviction in all US states.

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What are the warning signs of drowsy driving?

Some warnings signs you may experience that signify drowsiness while driving are:

  • The inability to recall the last few miles traveled,
  • Having disconnected or wandering thoughts,
  • Having difficulty focusing or keeping your eyes open,
  • Feeling as though your head is very heavy,
  • Drifting out of your driving lane, perhaps driving on the rumble strips,
  • Yawning repeatedly,
  • Accidentally tailgating other vehicles,
  • Missing traffic signs.

In fact, drowsy drivers sometimes drive so poorly that they might appear to be drunk. In a survey of police officers conducted by the AAA Foundation for Traffic Safety, nearly 90 percent of responding officers had at least once pulled over a driver who they expected to find intoxicated, but turned out to be sleepy (and not intoxicated).

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What are the specific at-risk groups affected by drowsy driving?

The specific at-risk group for drowsy-driving-related crashes comprises people who drive after having not slept enough, qualitatively or quantitatively. If you're tired and you're driving, you are at risk. In general, individuals who are “most at-risk for being at-risk” of drowsy driving include:

Young People : Sleep-related crashes are most common in young people, especially those who tend to stay up late, sleep too little, and drive at night - a dangerous combination. A study by the National Highway Traffic Safety Administration and the State of New York found that young drivers are more than 4 times more likely to have sleep-related crashes than are drivers over age 30.

Shift Workers and People with Long Work Hours : Shift workers and people who work long hours are at high risk of being involved in a sleep-related crash. The human body never fully adjusts to shift work, according to the National Sleep Foundation. The body's sleep and wake cycles are dictated by light and dark cycles, and generally will lead one to feel sleepy between midnight and 6 AM. For more information, see the National Sleep Foundation's Sleep Strategies for Shift Workers.

People with Undiagnosed or Untreated Sleep Disorders : Approximately 40 million people are believed to have some kind of sleep disorder. Many different sleep disorders result in excessive daytime sleepiness, placing this group at high risk for sleep-related crashes. Common sleep disorders that often go unnoticed or undiagnosed include sleep apnea, narcolepsy, and restless leg syndrome. You can learn more about these and other sleep disorders by visiting the National Sleep Foundation web site.

Business Travelers : Business travelers struggle with jet lag, a common sleep disorder that causes sleepiness and negatively affects alertness. “Jet lag” as well as long work hours put these weary travelers at increased risk for sleep-related crashes.

Finally, it is important to realize that although these specific groups of people are statistically most likely to be involved in drowsy driving crashes, one who does not fall into any of these groups is by no means “immune” to drowsy driving. “Average drivers” who don't happen to be under age 30, working the night shift, traveling for business, or suffering from sleep apnea are still at risk if they drive while fatigued.

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Do people realize how dangerous it is to drive while drowsy?

According to AAA Foundation for Traffic Safety research, the public perceives drowsy driving to be an important cause of motor vehicle crashes. Three out of four non-crash-involved drivers, and four out of five of those in recent crashes, said that driver drowsiness was “very important” in causing crashes. These results place drowsy driving as being less of a contributor to crashes in the public's view than alcohol, but more important than poor weather conditions, speeding, or driver inexperience. Drowsy driving and aggressive driving, which have both received fairly widespread media attention, were rated about the same.

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What can be done in advance to avoid drowsy driving altogether?

Get a good night's sleep : The amount needed varies from individual to individual, but sleep experts recommend between 7-9 hours of sleep per night.

Plan to drive long trips with a companion : Passengers can help look for early warning signs of fatigue, and switching drivers may be helpful. Passengers should stay awake and monitor the driver's condition.

Take regular breaks : Schedule regular stops - every 100 miles or 2 hours, even if you don't feel tired, and more often if you feel like you need it.

Avoid alcohol and medications : If medications warn that they cause or may cause drowsiness, avoid taking them before driving. If you must take certain prescription medications that cause drowsiness, don't drive immediately after taking them.

You should never consume alcohol before driving in the first place, but it is especially important to realize that alcohol interacts with fatigue, increasing sleepiness. If you are already tired, even a small quantity of alcohol may exacerbate your sleepiness and increase your risk of crashing, even if your BAC is well below the legal limit for a DWI conviction.

Consult your physician or a local sleep disorders center : If you suffer frequent daytime sleepiness, experience difficulty sleeping at night, and/or snore loudly on a regular basis, consult your physician or local sleep disorders center for a diagnosis and treatment.

For more information about sleep, sleep disorders, and the effects of sleeping too little, visit the National Sleep Foundation web site.

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When are drowsy driving crashes most likely to occur?

As intuition dictates and data confirms, most sleep crashes occur in the “middle of the night,” during the early morning hours. Less obviously, though, there is also a peak in sleep-related crashes in the mid-afternoon. Our natural circadian rhythms dictate that we will be most sleepy during the middle of our nighttime sleep period, and again about 12 hours later, between 2 PM and 4 PM, and various studies show a peak in crashes believed to be related to sleep somewhere between 2 PM and 6 PM.

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What if I'm already driving and I start to feel tired? What should I do? 

Take a nap. Naps are beneficial when experiencing drowsiness. Find a safe place (i.e., not the shoulder of the highway) where you can stop, park your car, and sleep for 15 to 20 minutes. A nap longer than 20 minutes can make you groggy for at least 15 minutes after awakening.

If you are planning a long trip, or routinely drive for long durations, identify safe places to stop and nap. If you only have a short distance remaining (e.g., an hour or so of driving), the nap might be enough to revive you. If you still have several hours of driving planned, and you're already feeling tired, it would probably be best to find a bed for the night, get a full night's sleep, and then resume driving.

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What about coffee? Won't that keep me awake?

Not necessarily. The “perk” that comes from drinking a cup of coffee may take a half hour or so to “kick in,” is relatively short in duration, and will be less effective for those who regularly consume caffeine (i.e., most people). If you're very sleepy, and rely on caffeine to allow you to continue driving, you are likely to experience “microsleeps,” in which you doze off for four or five seconds, which doesn't sound like long, but is still plenty of time to drive off of the road or over the centerline and crash.

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Should I open the window or turn up the radio to fight fatigue on the road?

No. Some of these tricks may help you to feel more alert for an instant; however, they are not effective ways to maintain an acceptable level of alertness for long enough to drive anywhere. Even with the window rolled all the way down and radio cranked up, if you're sleepy, you're still an unnecessarily great hazard to yourself and to everybody else on the road. If you're sleepy enough that you're seeking special measures to stay awake, you should have stopped driving already. Look for a safe and secure place, park the car, and take a nap.

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Are there any devices I can buy that will keep me awake while I'm driving?

There are a few devices on the market, some of which are worn on your body or placed in your car, that are advertised to keep drowsy drivers awake; however, to our knowledge, none of them have been scientifically validated yet. The only driver warning mechanism that has been validated to date is the shoulder rumblestrip, which produces noise and mechanical vibration if your vehicle drives on it. If you start driving onto the rumblestrip, this is an indication that you are too tired to drive safely. You should not rely on the rumblestrip to alert you every time you begin to doze off and drive off course - rumblestrips won't prevent you from crashing into other cars.

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References

National Highway Traffic Safety Administration

National Sleep Foundation