Drowsy Driving: A Prevention Guide

“Drowsy Driving” is a relatively common phenomenon: if you have enough experience as a driver, you have probably felt drowsy and less-than-fully-alert while behind the wheel at some point. You may therefore be tempted not to take drowsy driving seriously. Of course, this is a mistake. Drowsy driving is a significant problem in the United States, and can be deadly. Studies from the AAA Foundation for Traffic Safety found that drowsy driving may be involved in about 9% of all crashes, around 10.6% of crashes that resulted in property damage, airbag deployment, or injury, and up to one in six deadly crashes.

Let's explore the ins and outs of drowsy driving, including when, where, and why it happens, who is at risk, and what to do about it.

Drowsy Driving Statistics

Pretty much every driver has been there: it’s late, or you’ve had a long day, and you can feel your eyes getting heavy and your energy levels waning. If driving is your main form of transportation, as it is for around three-quarters of adults in the U.S., it’s quite common to have to drive somewhere when you’re feeling tired and therefore less than one hundred percent alert. However, this sort of drowsiness often goes far beyond just feeling like you could use a nap. One study showed that 31.5% of people admitted to having driven when they were so tired they could barely keep their eyes open, and around 43.2% of drivers reported having actually fallen asleep behind the wheel at some point in their lives (with 17.4% saying that this happened three or more times.)

Quite like many other things that may be common in the car and therefore easy to shrug off (such as texting while driving), drowsy driving can have serious consequences. A drowsy driver is an unsafe driver, and the decision to get behind the wheel while fatigued can do serious, potentially irreversible damage to the life of the driver and to those around them.

How does fatigue affect drivers?

Though it may seem simple, it’s worth pointing out the ways that fatigue behind the wheel impairs a driver.

Lack of sleep gets in the way of basic functions that are essential to driving safely. It reduces reaction time, negatively affects memory, makes it more difficult to focus and sustain attention, and dampens the driver’s situational awareness, as well as their ability to make sound decisions and avoid risk taking behaviors. This reduced awareness can even extend to the driver’s ability to tell just how tired they really are, which can lead to them getting on the road in such a state in the first place.

Drowsiness and fatigue also cause additional physiological effects that impede safe driving, such as reduced eye scanning, inability to keep the eyes open and the head up, and slackened muscles. Then, of course, there is the issue of actually falling asleep while driving. This can range from microsleep, or dozing off for a few seconds and then jolting back awake, to types of unawakened sleep onset which can cause the driver to veer into traffic or off the road. There are a few other important things to keep in mind when it comes to drowsy driving:

The drowsy driving problem in America is very closely linked to the larger problem of disordered or deficit sleep. According to CDC statistics, 83.6 million American adults--over one third--do not regularly get the recommended amount of sleep they need to be healthy. This is due to many factors, including a general cultural willingness to sacrifice sleep. According to a 2014 survey, 40% of 18-34 year olds and 33% of 35-54 year olds said they believed that in order to get ahead in their careers and take care of their families, they needed to survive on less than the recommended amount of sleep. The factors that lead Americans to drive while fatigued should be viewed within the context of why so many Americans get less sleep than they need to be healthy.

Is Driving Drowsy Like Driving Drunk?

One way to explain the seriousness of drowsy driving is to compare it to drunk driving. It may be surprising, but being significantly sleep deprived can cause similar impairments to being drunk, such as an inability to focus, lack of judgment, dampened reflexes, reactivity, and situational awareness, and a general propensity to fall asleep.

According to the National Safety Council, driving after going more than 20 hours without sleep is the equivalent of driving with a blood-alcohol concentration of 0.08%--the U.S. legal limit. Notably, just as you become increasingly impaired the more drinks you have, you also become increasingly impaired the more hours you go without sleep. If you go 24 hours without sleep, for instance, it’s as if you have a blood alcohol level of .10%, which is past the legal limit.

However, though driving while drunk and driving while sleep-deprived are similar in many ways, there are actually a few important differences between them. Providing a drunk driver doesn’t fall asleep, they may be able to drive slowly and try to react to the road. However, sleep-deprived drivers are much more likely to nod off while going fast, and they are therefore generally unable to brake or swerve in reaction to something in front of them.

In addition, while a significantly impaired drunk driver is likely to be spotted, breathalyzed, and taken off the road, there is no tool to measure significant impairment caused by sleep deprivation, and many officers do not know the signs. This means that even if a drowsy driver is driving erratically and is stopped, they are much more likely to be allowed to continue driving.

When Do Drowsy Driving Crashes Occur?

Drowsy driving occurs whenever a person gets on the road without getting enough sleep. This can happen at any time and in any context, providing that someone is both fatigued and driving. However, drowsy driving crashes tend to happen more when certain factors are in place, and the crashes themselves tend to have specific characteristics.

  • Time of Day: Most drowsy driving crashes occur between midnight and 6.AM, though a sizable amount of drowsy driving crashes happen in the afternoon, between approximately 2 and 4 PM. These are both time periods when the body’s natural circadian rhythm takes a dip toward drowsiness, and when someone who is already sleep deprived may feel the effects more significantly.
  • Single Car Occupant: Around 80% of fatigue-related crashes happen when a person is in a car on their own. This may be because having another person around keeps a person more alert because another person in the car is likely to notice a person dozing off and wake them up, or for various other reasons. However, it is clear that driving while drowsy on your own increases your likelihood of crashing.
  • High Speed Roadways: The majority of crashes due to drowsy driving happen on high speed roadways, such as highways and interstates, and rural roads, where there can be long, monotonous stretches of uninterrupted driving, often without seeing another car. The continued straight driving without additional stimuli to react to can lull a drowsy driver into inattention and further sleepiness.
  • Often Has Single Vehicle Leaving Roadway: One of the key markers of a drowsy driving crash is veering off the side of the road. This happens when the driver drifts off and stops controlling the steering wheel, which causes the vehicle to swerve to the side.
  • No Attempt to Break: In drowsy driving crashes, there is often no attempt to break (and, if there is an attempt, it is severely delayed). This is because the drowsy driver is usually not fully conscious in the lead up to the crash, so they would not know to press down on the break to avoid it like they may in other types of accidents.
  • Likely to be Serious: Because, as aforementioned, the driver is usually not fully conscious during a drowsy driving crash and therefore cannot make pre-emptive attempts to avoid damage, drowsy driving crashes tend to be quite serious.

Highest-Risk Drivers

Drowsy driving crosses all denominations: age, sex, gender, ethno-racial identity, class, occupation--you name it. Anyone who doesn’t get enough sleep and gets behind the wheel of a car can be a drowsy driver, which is what makes the problem so pervasive.

That said, there are certain populations at an increased risk for drowsy driving.

Young People

When it comes to age, young people--specifically those aged 16 to 24--are more likely than any other age group to drive while drowsy.  It is estimated that people in this age group are involved in more than half of all drowsy driving accidents annually. This is due to a number of factors.

For one, young people simply do not get enough sleep. This may seem like an old man’s complaint about “kids these days”, but it’s actually proven to be true. In order to be healthy, teenagers need at least 8.5 to 9.5 hours of sleep. Altered sleep drives caused by the delayed release of melatonin, as well as school, work, social demands, technology, and generally mismanaged sleep hygiene, cause many teenagers to stay awake later. Since they generally have school early in the morning, they often do not have enough time to sleep and are therefore regularly sleep-deprived.

 

According to a comprehensive, longitudinal study by the CDC, over 70% of teenagers reported sleeping less than eight to nine hours a night. Meanwhile, 30% of teenagers reported sleeping less than 7 hours a night, 22% reported sleeping less than six hours, and 10.5% reported sleeping less than five hours. Coupled with driving inexperience and a generally underdeveloped ability to sense and avoid risk, this chronic sleep deprivation creates an increased risk of drowsy driving in teenagers.

This trend continues and even worsens into the college years. A combination of the lack of parental supervision and increased academic pressure leads to even less regular sleep in college students. This is compounded by “social jet lag” (or, the drastic difference in sleep schedules between weekdays and the weekend), which, according to researchers, is the equivalent of flying from New York to Denver and back every weekend. More than two-thirds of college students report experiencing excessive drowsiness, and more than a third report falling asleep in class at least once a week. This state of drowsiness can clearly extend to a college student’s ability to function behind the wheel.

It should also be noted that young men are more likely than young women to drive while drowsy. Studies show that young men are five times more likely than young women to get into fatigue-related car crashes. The reason for this is not entirely clear, since both young men and young women show similar rates of sleep deprivation. However, it could be due to the fact that men at any age are more likely to drive while drowsy than women women at any age, as stated above.

Shift Workers

Around 9.5 million people, or 15% of the American workforce, are shift workers, meaning they do not work a regular 9 to 5, Monday to Friday job, but rather work night or rotating shifts. This includes people like factory and warehouse workers, manufacturers, doctors and nurses, police officers, EMTs, home health aides, hospitality workers, taxi drivers, nannies, group home workers, and night watchmen, among others. Shift-based jobs often have long and/or irregular hours, which force employees to work against their bodies’ natural circadian rhythms, and which therefore frequently cause sleep disruption and regular sleep loss.

This increased risk of sleep deprivation among shift workers translates into an increased risk of drowsy and fatigued driving. In order to examine the effect of shift work on daytime driving, one study used driving simulators on shift workers after a night of work and after a night of sleep. A staggering 37.5% of the participants who were coming from a night of work had a crash or near-crash event. Meanwhile, after a night of sleep, the same participants had zero near-crashes. The study found that even seasoned, experienced, and long-term shift workers were at risk for drowsy driving after a night shift.

Because of the professional capacities of some shift workers, this can have a serious impact both on the individual and on the general public. Take, for instance, police officers. A study of North American police officers found that 46% of them reported falling asleep while driving, with around 25% of them saying it happened at least one or two times a month. The study also indicated that around 40% of examined officers tested positive for significantly disruptive, serious sleep disorders (which is almost double the rate of the general population), and that sleep deprivation was the cause of as many as 50% of on-the-job accidents and injuries involving officers.

Commercial Drivers

Commercial drivers, especially long-haul truckers, are at a significant risk of drowsy driving. With extended, often irregular hours and treks down unbroken stretches of highway, fatigue is basically considered a “part of the job” for truckers and other commercial drivers. According to a congressionally mandated study by the National Transportation Safety Board in 2013, 12.7% of all fatal crashes and 6.8% of non-fatal crashes involved at least one truck or large bus. Of those, around half were likely caused by fatigue.

The long work hours of a commercial driver, as well as the economic pressure to deliver on or before the deadline, contribute to the significant degree of sleep deprivation in that population. Recent studies have found that commercial drivers averaged 5 to 6.2 hours of sleep per workday, and that 13% of commercial drivers regularly operate their vehicles while fatigued (though that figure may be quite low, due to under-reporting.) This can lead to drivers falling asleep behind the wheel, as was found in one study, where 25% of the interviewed drivers reported having fallen asleep while driving at least once. Falling asleep and losing control of such a large vehicle is particularly dangerous, both for the driver and other motorists: on average, for each accident-based truck driver fatality, three to four other people are also killed.

Business Travelers

People who regularly travel for business are at risk for drowsy driving in a number of ways. Business travel often involves getting up early and staying up late, extended periods time in potentially uncomfortable motels, jet lag, and the stress of meetings and presentations, all of which may lead to significant sleep disturbances.

For people who regularly drive for business, such as salesmen, long trips on the road with pressure to adhere to strict time frames and quotas may also lead to drowsy driving. This, combined with a general corporate ethos that encourages people to push themselves as hard as they can, may lead to business travelers continuing to drive even when they begin to feel the effects of fatigue.

Parents of Young Children

Having a baby causes a sudden and extremely abrupt change to a person’s sleep patterns, defined by regular sleep disturbance. Ask anyone who has an infant in the house, and they’ll tell you that a good night’s sleep is hard to come by. New mothers and fathers experience significant sleep fragmentation, low sleep efficiency, less total sleep time, and increased fatigue. Depending on the child, these sleep disturbances can go on for years: 50% of American parents report losing at least 30 minutes of sleep per night due to their child’s awakenings.

These regular and often significant sleep disturbances can affect the day to day functions of parents, especially new parents, who are still adjusting to the lack of regular sleep. This can easily translate into fatigued and drowsy driving.

Drivers on Certain Medications

A number of medications can cause drowsiness and fatigue. This is true for both prescription and over the counter medications. These medications can impair even a well-rested driver due to their soporific effects. A number of studies have indicated that using these medications while driving increases the risk of sleepiness related crashes. The risks are higher with higher drug doses, for people taking more than one medication simultaneously, for people mixing medications with narcotic drugs or alcohol, and for people taking drowsiness-inducing medications who are already sleep deprived. Medications that commonly cause drowsiness include:

  • Narcotic pain medications (such as Oxycontin and Hydrocodone)
  • Hypnotics (such as Ambien and Halcion)
  • Benzodiazepines (such as Xanax and Valium)
  • Tricyclic antidepressants (such as Amitriptyline and Doxepin)
  • Sleeping aids (such as Sonata and Lunesta)
  • Sedating prescription antihistamines (such as Hydroxyzine)
  • Tranquilizers (such as Ativan and Klonopin)
  • Over the counter meds (such as Benadryl and Nyquil)
  • Muscle relaxants (such as Zanaflex and Dantrium)
  • Some high blood pressure medications (such as beta blockers, Methyldopa, and Angiotensin II receptor blockers)

Drivers with Sleep Conditions

One of the biggest populations at risk for drowsy driving, perhaps obviously, is drivers who have underlying sleep conditions. Sleep disorders are incredibly common. Approximately eighty types of sleep disorders affect around 164 million Americans, around 68% of the population.

Individuals with sleep disorders are at a significant risk for increased fatigue, which can lead directly to drowsy driving. People who suffer from the most statistically prevalent sleep disorders (namely, insomnia, sleep-apnea/sleep-disordered breathing, and narcolepsy) are each at risk for drowsy driving in different ways.

Those who suffer from insomnia are often chronically sleep deprived, and therefore may experience significantly impaired cognitive function, inattention, and general fatigue. Narcolepsy is obviously also dangerous, since it causes generalized fatigue regardless of how many hours of sleep a person gets, and, in some people, can cause relatively sudden sleep onset. In severe cases of narcolepsy, patients are generally advised to reduce their driving time, or cut out driving altogether.

Sleep apnea and sleep disordered breathing, which is the obstruction of the airways during sleep, can be particularly dangerous when it comes to drowsy driving for a number of reasons. For one, it is often undiagnosed: though it is estimated that 22 million Americans have some form of sleep apnea, with a whopping 80% of cases undiagnosed or under-diagnosed. If left untreated, apnea can cause many health issues, including extreme daytime fatigue. People with sleep apnea are also more likely to fall asleep during the day--including while driving. Studies have shown that those with untreated sleep apnea are seven times more likely than the average person to fall asleep behind the wheel, and are significantly more likely to get into fatigue-related auto crashes.

Safety and Prevention

Clearly, drowsy driving is a serious issue and needs to be addressed. That’s why health officials, governments, civic planners, and various other individuals and agencies have made a concerted effort to spread awareness about drowsy driving and to help them prevent and fight it.

Warning Signs

Perhaps the most important way to prevent drowsy driving based accidents is to know the warning signs. It’s important to be aware of your fatigue levels while driving. If you start to experience the following signs, it’s time to pull over and rest. They include:

  • Frequent blinking
  • Head nodding and inability to keep your head upright
  • Eyelid heaviness and inability to keep your eyes open
  • Repeated yawning
  • Reduced tracking and trouble focusing your eyes
  • Blurry vision
  • Memory lapses and difficulty focusing attention
  • Missing exits
  • Daydreaming and/or wandering or disconnected thoughts
  • Suddenly jolting awake (after microsleep)
  • Drifting between lanes or onto the shoulder of the road

Personal Prevention Tips

In addition to being aware of the warning signs and pulling off the road when you feel them, there are also a number of other preventative measures you can take to avoid drowsy driving and the associated accidents.

  1. Get a good night’s sleep. Though this is obviously much easier said than done, it is worth it to try to make a concerted effort to get enough sleep on a regular basis. This is especially true when you know you are going to spend a significant amount of time behind the wheel. For instance, if you know you’re about to drive to another state for a concert, on Tuesday, make an effort on Monday night to get as much sleep as possible.
  2. Plan trips with sleep in mind. In addition to getting enough sleep before trips, you should also factor sleep into your plans when you know you’re going to be driving for an extended amount of time. Whenever possible, schedule your driving for times when you are normally awake, and plan overnight stops during your regular sleep hours rather than driving straight through. You should also schedule a break every two hours or so for long haul trips, to avoid getting road fatigue, and should avoid planning to work all day and drive through the night without sleeping.
  3. Be smart about driving hours. If this is at all possible, avoid driving between the hours of 12 a.m. and 6 a.m. and between the hours of 2 p.m. and 4 p.m. Though it may be impractical or even impossible to avoid driving during these hours, it is helpful to reduce the amount of time you're on the road while your circadian rhythms are in a drowsy downswing. If you must drive during peak sleepiness hours, be vigilant about signs of drowsiness and check in with yourself at regular intervals so you know when to pull over and take a break.
  4. Travel with a friend. The vast majority of drowsy driving crashes happen when someone is driving on their own. Carpooling is ecologically friendly and saves gas money, and has the added benefit of reducing the risk of a drowsy driving crash. It is especially helpful to bring a friend with you if you plan on driving overnight, or at any point during the 12 a.m.-6 a.m. time period.
  5. Utilize naps. When it comes to combating drowsy driving, naps are your friend. If you feel like you might be headed toward drowsiness in the hour or so before you’re planning on driving, take a quick nap before you leave to recharge. Naps can also be a crucial tool if you’re hit with drowsiness while on the road. Don’t be afraid to pull over and take a short nap (around 20 or so minutes is recommended), and give yourself around 15 minutes to fully wake up afterward, since you will likely still be slightly groggy. If you still feel significantly fatigued after the nap, it’s best to find a place to stay for the night rather than continuing to drive.
  6. Use Caffeine for a Short-Term Boost. Caffeine can definitely help if you’re feeling tired while driving, but it should be used with its limitations in mind. Drinking around 1-2 cups of coffee will increase your alertness on the road. However, it generally takes 30 minutes for caffeine to enter the bloodstream. Therefore, if you are significantly drowsy, it is suggested that you pull over and take a 20-30 minute nap after drinking your coffee or caffeinated beverage.

Take Action to Combat Drowsy Driving

There are also a number of steps that can be taken on an institutional level to help prevent drowsy driving. These are important efforts that individual people can support by advocating, lobbying, and voting for them in their own communities.

Spread the Word

As previously mentioned, the information we have on the prevalence of drowsy driving is almost certainly under-reported. More accurate and extensive research is needed to understand exactly how bad the problem is, who is most at risk, and what the best solutions are. This can be addressed by improving police accident reports, improving crash site investigator training, and funding research on drowsy driving using existing and innovative research methodologies. Researchers also need to develop biomarkers (reliable biological indicators) of sleep deprivation. Developing sleep deprivation biomarkers may potentially lead to the development of sleep deprivation detection technology, which could be used the same way an alcohol breathalyzer or a drug test is today.

Employer Policy Changes

Businesses should be pushed and encouraged to adopt anti-drowsy driving and sleep health promotion policies--especially in industries that employ shift workers. Evidence-based fatigue management programs should also be adopted, such as the North American Fatigue Management Program, which was developed for commercial drivers. Industry standards should be set that prevent workers from being on shift and awake for unsafe amounts of time--both in terms of consecutive hours, and in terms of the number of hours worked in a week. This is especially true in fields like commercial driving, but also in medicine, aviation, factory/warehouse work, manufacturing, and many others. Sleep health promotion policies should also be implemented in non-shift-work atmospheres. “Nap rooms”, for instance, are increasingly common at more socially minded companies. These policies can also target larger cultural change toward valuing sleep: Aetna, for instance, instituted a wellness program where employees--as tracked by FitBit--got financial incentives for getting regular seven-hour nights of sleep in a row.

School Policy Changes

One of the most significant changes that can be made to the high rates of drowsy driving among teens is to change school hours: namely, to establish later start times for schools. In 2014, the American Academy of Pediatrics issued a policy statement urging middle and high schools to shift their start times to 8:30 AM or later, stating that this would significantly lower the sleep deprivation rates among teenagers, and would therefore decrease their risk of getting into fatigue-related accidents (among other negative outcomes).
Schools should also implement educational programming about drowsy driving in their driver’s ed curriculums. As of 2015, only 11 states required driver’s education programs to include drowsy driving. Modules like the one required for all driver’s ed programs in Massachusetts, which explains the physiology of drowsy driving and how to prevent it, have been shown to increase awareness about drowsy driving among high school aged students.

Engineering Changes

Civil engineers, city planners, and road construction experts have proposed numerous changes that can be made to the average road in order to address drowsy driving. They include:

  • Rumble Strips: Rumble strips are lengths of raised material placed on the edge of the road that produce both a loud noise and a vibration when a vehicle’s tires travel across them. This helps alert drowsy drivers that they are veering toward the edge of the road and may prevent them from crashing.
  • Median Cable Barriers: These cable barriers are used to replace guard rails on highway medians. They prevent cross-median head-on crashes by flexing when hit by a vehicle, which absorbs much of the crash force and redirects the vehicle along the median. This is particularly helpful for drowsy drivers, as one of the deadliest types of drowsy driving accidents occurs when a person falls asleep and veers through a median barrier into the opposite lane.
  • Rest Areas: Places to stop along the road are essential when it comes to responsibly handling drowsy driving risks. Advertising existing rest stops and adding additional rest stops (especially on rural roads) is key to helping road-weary travelers stop and take a nap to prevent an accident. Rest stops don’t have to be elaborate or expensive: they can simply be clearings by the roadside where a person can pull over and sleep.

Drowsy Driving Advocacy & Resources

In the end, one of the most important efforts when it comes to fighting drowsy driving is raising awareness about the problem. A number of individuals, non-profits, foundations, grassroots groups, and legal bodies have made significant strides in anti-drowsy-driving advocacy  Here are some important movements related to combating drowsy driving:

Additional Resources

Drowsydriving.org: The National Sleep Foundation’s resource hub for all things related to drowsy driving. Go here for information on National Drowsy Driving Prevention Week 2019, as well as drowsy driving associated facts, resources, and media.

Drowsy Driving: Asleep at the Wheel: This drowsy driving page, put together by the CDC, has up to date statistics, infographics, and health information.

NHTSA Drowsy Driving Site: The National Highway and Transportation Safety Authority’s comprehensive rundown on drowsy driving, who it affects, and how to stop it.

Drowsy Driving by the National Center for Health Research: Authored by Daniel Mansfield, MPH, this is essentially a white sheet for drowsy driving-related problems and solutions from a public health perspective.

The Dangers of Drowsy Driving: Consumer Report’s extensive, well-researched article on drowsy driving, written by Catherine Roberts.

AAA’s Drowsy Driving Advice: A Q and A section from AAA about drowsy driving, when it’s time to pull over, and what you can do to keep alert.

Current Summaries of Drowsy Driving Laws: This is a list put together by the National Conference of State Legislatures, which has all current laws and all bills proposed in state legislatures about drowsy driving.

Drowsy Driving Curriculum: Healthychildren.org’s curriculum about drowsy driving, aimed toward teens and young adults.

Drowsy Driving Prevention Tips: A helpful tip sheet from Loyola University in Chicago.

Wake Up Call!: An elaborate, thorough examination of drowsy driving from many different angles, put together by the Governor’s Highway Safety Association.

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