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Dangers of Driving Drowsy

According to the National Sleep Foundation, more than half of American adult drivers have admitted to driving drowsy, and almost one in five admit to having fallen asleep behind the wheel. The National Highway Traffic Safety Administration (NHTSA) estimates that around 100,000 car crashes reported to the police each year are a result of sleepiness and fatigue. This is a rough estimate as it is difficult to pin down exactly how many crashes are actually due to drowsiness.

Dangers of Drowsy Driving
Dangers of Driving Drowsy

Drowsy driving accidents are difficult to put an exact figure on for many reasons. One is that there is no test to determine driver fatigue like there is for drunk driving. Also, a large number of crashes associated with drowsy driving are often fatal. However, according to the NHTSA, there are some common factors that accident investigators use to determine that a crash was caused by driving while fatigued:

• Though driving drowsy can affect all types of crashes both day and night, they occur most frequently between midnight and 6 a.m., or in the late afternoon- both of which are times when there are dips in the circadian rhythm.
• Many drowsy-driving crashes involve only a single vehicle, with no passengers besides the driver running off the road at a high rate of speed with no evidence of braking.
• Drowsy-driving crashes frequently occur on rural roads and highways.

According to NHTSA’s National Motor Vehicle Crash Causation Study (NMVCCS), drowsy drivers involved in a crash are twice as likely to make performance errors as compared to drivers who are not tired. When a person drives while tired their reaction time, judgment, alertness, attention, and decision-making are all compromised which leads to a greater chance of crashing. In some cases, a drowsy driver will fall asleep at the wheel. Most people associate impaired driving with alcohol or drugs, but studies have shown that driving when fatigued can be as dangerous as driving under the influence. In fact, someone who has been awake for 17 hours has the response time of someone with a blood alcohol content (BAC) of 0.05%. After 24 hours of sustained wakefulness, the impairment is equal to 0.10% BAC. (In all of the US, a BAC of 0.08% is considered legally drunk.) Simply put, driving drowsy has a negative impact on a person’s ability to drive safely.


Who’s at risk?

The National Sleep Foundation’s webpage states that although anyone who drives is at risk of falling asleep at the wheel, some groups of people are more at risk than others:

Shift workers and people working long hours– People who work rotating shifts, double shifts, night shifts or work more than one job have a six-fold increase in drowsy driving crashes.
• Commercial drivers– Those who drive a high number of miles and drive at night are at significantly higher risk for fall-asleep crashes. Commercial drivers have also been found to be at a high risk for sleep disorders.
• People with untreated sleep disorders such as obstructive sleep apnea (OSA)– People with untreated OSA are up to seven times more likely to have a drowsy driving crash. For some people insomnia can increase fatigue.
• Young drivers– Combining inexperience with sleepiness and a tendency to drive at night puts young people at risk, especially males aged 16-25 years.
• Business travelers– Frequent travelers who may be suffering from jet lag and crossing time zones, spending long hours behind the wheel or getting too little sleep.

Though the groups listed above are the most vulnerable to falling asleep and crashing while driving, everyone has the potential to cause a fatigue related accident. Your risks for a drowsy driving accident increases when you are:

• Driving long distances without proper rest breaks
• Working 60 hours or more a week
• Sleep deprived and/or fatigued
• Drinking alcohol
• Driving alone, especially on long, dark, rural, or boring roads
• Taking medications such as antihistamines, cold tablets, or antidepressants
• Experiencing jet lag


Warning Signs of Fatigue or Sleepiness

Most people are not very good at determining when they are too tired to get behind the wheel. Often times they don’t realize they are too tired until they are well into their drive. However, there are key warning signs to tell you when you are too tired to drive that you should take into consideration:

• Turning up the radio or rolling down the window
• Impaired reaction time and judgment
• Decreased performance, vigilance and motivation
• Trouble focusing, keeping your eyes open or your head up
• Daydreaming and wandering thoughts
• Yawning or rubbing your eyes repeatedly
• Drifting from your lane, tailgating and missing signs or exits
• Feeling restless, irritable or aggressive



The best thing that you can do to prevent drowsy driving on a daily basis is to always get enough rest. Getting enough sleep is the one true way to prevent against the risks of drowsy driving. Make it a priority to get the recommended 7-8 hours of sleep per night. The National Sleep Foundation and NHTSA also offer these tips to help you avoid a drowsy driving accident:

• Watch for the above warning signs of fatigue.
• If you notice that you are feeling any of the above signs of fatigue, Stop Driving– pull off at the nearest exit or rest area, or find a place to sleep for the night.
• Take a nap- find a safe place to nap for 15-20 minutes (a nap longer than 20 minutes can make you groggy for 15 or minutes after waking).
• Consume caffeine- the equivalent of two cups of coffee can increase alertness for several hours, and usually takes about 30 minutes to enter the bloodstream. Caffeine is available in various forms (coffee, tea, soft drinks, energy drinks, chewing gum, tablets), and in various amounts. For example, the amount of caffeine in one cup of coffee (about 135 mg) is about the same as 2-3 cups of tea or 3-4 cans of regular or diet cola. DO NOT rely on this for long periods of time.
• Consume caffeine just before taking a short nap to get the benefits of both.
• Don’t drive if you are tired or on medication that may cause drowsiness.
• If you are not alone, have a passenger take over driving.
• Avoid driving at times you would normally be sleeping.
• Don’t consume any alcohol before driving. Alcohol interacts with sleepiness to increase drowsiness and impairment.
• Get treatment for sleep disorders such as obstructive sleep apnea, insomnia, narcolepsy and restless legs syndrome.
• Take a break every two hours if you are driving long distances.
• For your safety, always wear your seatbelt.


Drowsy driving can be deadly and it is something we should take seriously. When we drive we take responsibility for our personal safety as well as the safety of others on the road with us. Be sure that you are using safe driving practices, including avoiding driving drowsy, so that you can remain alert and arrive to all of your destinations alive.