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Scope of the Problem

Precise counts of crashes caused by drowsy driving are not yet possible. Crash investigators can look for certain clues that drowsiness was likely to have contributed to driver error, but these clues are not always identifiable or conclusive. In lieu of consistent and conclusive evidence, researchers have used various methods to estimate the overall number of crashes or crash fatalities caused by driver drowsiness. These methods range from counts of crash reports where police-reports indicate drowsiness as a contributing factor, to statistical estimates based on crash reports and surveys of self-report crashes or driving experience.

In 2014 there were 846 fatalities (2.6% of all fatalities) recorded in NHTSA’s FARS database that were drowsy-driving-related. These reported fatalities (and drowsy-driving crashes overall) have remained largely consistent across the past decade. Between 2005 and 2009 there was an estimated average of 83,000 crashes each year related to drowsy driving. This annual average includes almost 886 fatal crashes (2.5% of all fatal crashes), an estimated 37,000 injury crashes, and an estimated 45,000 property damage only crashes.

There is ongoing research and discussion about how best to measure the impact of drowsy driving on crashes. A variety of research approaches and data indicate that traditional measures of drowsy driving may significantly underestimate the prevalence of the issue. Researchers have inferred the existence of additional drowsy-driving crashes by looking for correlations with related factors such as the number of passengers in the vehicle, crash time and day of week, driver sex and crash type. One such study from the AAA Foundation for Traffic Safety analyzed data from NHTSA's National Automotive Sampling System (NASS) Crashworthiness Data System (CDS). By using a multiple imputation methodology they estimated 7 percent of all crashes and 16.5 percent of fatal crashes involved drowsy driving. If this estimate is accurate, it suggests that more than 5,000 people died in drowsy-driving-related motor vehicle crashes across the United States last year. The 2009 Massachusetts Special Commission on Drowsy Driving, based on a different research methodology, estimated that there could be as many as 1.2 million crashes, 8,000 lives lost, and 500,000 injuries due to drowsy driving each year.

Crashes and Fatalities Due to Drowsy Driving

Crashes caused by drowsy driving often exhibit a set of common factors. Although sleepiness can affect all types of crashes during the entire day and night, drowsy-driving crashes most frequently occur between midnight and 6 a.m., or in the late-afternoon – both times when there are dips in your circadian rhythm (the internal human body clock that regulates sleep). Many drowsy-driving crashes also 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 also frequently occur on rural roads and highways.

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Did You Know?

  • Over the last decade, more than 7,000 people have been killed in drowsy-driving-related crashes.

  • Alcohol, in addition to its other detrimental effects on driving, can magnify the effects of drowsiness and cause you to fall asleep at the wheel more easily.

  • Use of prescription or over-the-counter medications can also heighten the effects of drowsiness.

  • Who is most at risk? While no one is immune, the following groups are at highest risk, based on evidence from crash reports and self-reports of sleep behavior and driving performance:

    • Young male drivers (17-23 years old)

    • People with sleep disorders, such as sleep apnea, insomnia, restless leg syndrome, or narcolepsy

    • Shift workers who work at night or who work long or irregular hours

    • People who sleep less than 6 hours per night

Tips to Avoid Drowsy-Driving Crashes

  • The best countermeasure to drowsy driving is to get enough rest on a daily basis. Sleep is the only true preventative measure against the risks of drowsy driving. Make it a priority to get 7-8 hours of sleep per night.

  • Before the start of a long family car trip, get a good night’s sleep, or you could put your entire family and others at risk.

  • Many teens do not get enough sleep at the same time that their biological need for sleep increases, thereby increasing the risk of drowsy-driving crashes, especially on longer trips.

  • Avoid drinking any alcohol before driving. Consumption of alcohol interacts with sleepiness to increase drowsiness and impairment.

  • If you take medications that could cause drowsiness as a side effect, use public transportation when possible. If you drive, avoid driving during the peak sleepiness periods (midnight – 6 a.m. and late afternoon).

  • If you must drive during the peak sleepiness periods, stay vigilant for signs of drowsiness, such as crossing over roadway lines or hitting a rumble strip, especially if you’re driving alone.

Short-Term Interventions

  • Drinking coffee or energy drinks alone is not always enough. They might help you feel more alert. However, the effects last only a short time, and you might not be as alert as you think you are. If you drink coffee and are seriously sleep-deprived, you still may have “micro sleeps” or brief losses of consciousness that can last for four or five seconds. This means that at 55 miles per hour, you’ve traveled more than 100 yards down the road while asleep. That’s plenty of time to cause a crash.

  • If you start to get sleepy while you’re driving, drink 1-2 cups of coffee and pull over for a short 20-minute nap in a safe place, such as a lighted designated rest stop. This has been shown to increase alertness in scientific studies but only for short time periods.

Latest News

Assessing the Feasibility of Vehicle-Based Sensors to Detect Drowsy Driving

The goal of this research was to determine the feasibility of detecting drowsiness with vehicle-based sensors and the extent to which alcohol-impairment algorithms could detect drowsiness and distinguish it from alcohol impairment. Results showed that differences in alcohol impairment and drowsiness impairment prevent a single algorithm from detecting both types of impairment; rather, a more complex approach involving multiple algorithms is necessary.

Using an advanced driving simulator, data were collected from 72 participants during daytime (9 a.m. - 1 p.m.), early night (10 p.m. – 2 a.m.), and late night (2 a.m. - 6 a.m.) sessions to provide data for algorithm testing and refinement. Driving data indicated a complex relationship between driving performance and conditions associated with drowsiness: compared to the daytime session, driving performance improved during the early night session before degrading during the late night session. These findings provide a better understanding of the relationship between impairment from alcohol and drowsiness and lay the foundation for detecting and differentiating among impairment from alcohol, drowsiness, fatigue and drugs. DOT HS 811 358 (1.6 MB PDF)

Additional NHTSA Research

  • Completed Research Studies

    • Assessment of a Drowsy Driving Warning System for Heavy-Vehicle Drivers A field operational test of an early prototype Drowsy Driver Warning System was conducted based on research and laboratory studies by NHTSA and FMCSA. This project included Control and Test groups consisting of 102 drivers from 3 for-hire trucking fleets using 46 instrumented trucks. Fifty-seven drivers were line-haul, and 45 were long-haul operators. This system uses a near-infrared camera coupled with processing equipment to estimate the driver’s percentage of eye-closure, which has proven to be a reliable measure of driver drowsiness. Results showed that drivers in the Test Group were less drowsy. Drivers with favoring opinions of the system tended to have an increase in safety benefits. Results of the assessment revealed that the early prototype device had an overall positive impact on driver safety. DOT HS 811 117 (PDF 7MB)

    • Development and Testing of Countermeasures for Fatigue-Related Highway Crashes Focus groups of young men and shift workers were convened to gain insight into their experiences, behavior, attitudes, and perceptions regarding drowsy driving. Additional focus groups were conducted to identify possible educational strategies and safety messages that would help them to change behavior or lifestyle choices that contributed to drowsy driving. (Read more)

    • Drowsy Driving and Automobile Crashes An expert panel on driver fatigue and sleepiness was convened to identify and articulate key issues involved in the drowsy-driving problem. Sponsored by the National Center on Sleep Disorders Research of the National Institutes of Health, and NHTSA, this 1998 report provided the foundation for developing future countermeasures on drowsy driving. (Read more)

    • National Survey of Distracted and Drowsy Driving Attitudes and Behaviors Report A survey of drivers was conducted in 2002 to collect data on the nature and scope of the drowsy-driving problem. Thirty-seven percent of drivers had nodded off for at least a moment or fallen asleep while driving at least once:

      • Eight percent had done so in the past six months.

      • Characteristics of Drowsy-Driving Trips:

      • Nodding off or falling asleep recently was most prevalent among drivers ages 21-29 (13%) and males (11%) and least prevalent among drivers over age 64 (4%) and females (5%).

      • Characteristics of Drowsy-Driving Trips:

        • Driver averaged 6 hours of sleep the previous night (and 24% had slept fewer than 5 hours)

        • Driver had been driving for an average of 2.9 hours (but 22% had been driving for more than 4 hours)

        • Occurred while driving on an interstate type highway with posted speed limits of 55 mph or higher (59%)

        • Nearly half (48%) nodded off between 9 p.m. and 6 a.m. (Read more) DOT HS 809 566

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