Drowsy Driving and Traffic Safety

Drowsy Driving and Traffic Safety

How to Combat Drowsy Driving

Smart Motorist recommends that drivers get sufficient sleep, don't drink alcohol when sleepy, pull over when drowsy, and limit their driving at night - especially between midnight and 6 a.m.

What causes drowsy driving? - Driver fatigue and inattention. NHTSA data indicate that in recent years, driver drowsiness or fatigue causes 56,000 crashes annually, as cited by police. Annually, roughly 40,000 nonfatal injuries and 1,550 fatalities result from these crashes. These statistics vastly underreport the extent of these fatigue-related crashes. (Also, these statistics also do not deal with crashes caused by driver inattention, a much larger problem.)

Who Is At Risk? - Although no driver is immune, the following five population groups are at highest risk, based on evidence from crash reports and self-reports of sleep behavior and driving performance.

  • Young People - especially males aged 16 to 29 with irregular sleep patterns and those who drive long distances late at night.
  • Shift Workers - employees whose sleep is disrupted by working at night or working long or irregular hours.
  • Victims of Sleep Disorders - people with untreated Sleep Apnea Syndrome (SAS) and narcolepsy.
  • People taking medications - Sedating medications, especially prescribed anxiolytic hypnotics (for example Valium), tricyclic antidepressants such as nortriptyline, antihistamines like Benadryl, and alcohol or codeine-containing products (e.g. Tylenol 3 - Nyquil) often cause drowsiness.
  • Drunk Drivers - Alcohol adds to drowsiness.

Warning - If you are in more than one risk group, be aware that a combination of these factors has a cumulative effect and substantially increases the risk of a drowsy driving incident.

What else contributes drowsy-driving crashes?

  • Sleep Deprivation - Sleepiness impairs driving performance by lengthening reaction time, decreasing vigilance and attention, and slowing information processing. Of course it can ultimately lead to falling asleep at the wheel. The loss of one night's sleep gives extreme short-term sleepiness; habitually restricting sleep by 1 or 2 hours a night leads to chronic sleepiness. Sleep is a neurobiologic need. Sleeping is the most effective way to reduce sleepiness.
  • Unusual Driving Patterns - These include driving between midnight and 6 a.m.; driving a substantial number of miles each year and/or a substantial number of hours each day; driving in the mid afternoon hours (especially for older persons); and driving for long stretches without taking a break. Federal regulations allow drivers of large trucks to drive up to 16 hours a day. However, drivers under the regulations can compile 60 hours in less than five days by alternating the ten hours of maximum permitted continuous driving with the minimum eight hours off duty. Surveys reveal that many drivers of large trucks violate the regulations on hours of service. Studies also show that driver fatigue plays a role in large truck crashes, and that truck drivers are more likely to crash after many hours of driving.

What are the characteristics of a drowsy driving incident?

Subjective and objective tools are available to approximate or detect sleepiness in the lab. However, no test currently can quantify sleepiness at the crash site. Although current understanding largely comes from inferential evidence, a typical crash related to sleepiness has the following characteristics:

  • It occurs during late night, early morning, or mid afternoon.
  • It is likely to be serious.
  • The crash occurs on a high-speed road or expressway (speed limit of 55-65 mph).
  • A single vehicle leaves the roadway.
  • The driver is alone in the vehicle.
  • The driver's eyes are closed.
  • The driver does not attempt to avoid a crash.
  • Evidence of a corrective maneuver, such as skid marks or brake lights, is absent.

How can I reduce drowsy driving incidents?

  • Plan ahead to reduce your risk of getting sleepy or actually falling asleep behind the wheel:
  • Get adequate sleep before taking a long drive.
  • Drive during normal waking hours.
  • Avoid all alcohol before driving.
  • Limit night-time driving, especially between midnight and 6 a.m.
  • Plan trips to avoid drowsy or fatigued times.
  • Schedule rest breaks on long journeys.
  • Plan on multiple drivers on long journeys.
  • Avoid large meals before a long drive - a full stomach can make you drowsy (especially turkey).
  • If drowsy, pull over and stop driving - get some sleep at a rest stop.

Two remedial actions can make a short-term difference in driving alertness:

  • Taking a short nap (at least 20 to 30 minutes)
  • Consuming the caffeine equivalent of two cups of coffee.

The following behaviors are scientifically unproven and probably won't keep you awake while driving:

  • Turning up the volume of your radio
  • Singing loudly
  • Chewing gum or eating food
  • Getting out of the car and running around
  • Slapping or pinching yourself
  • Sticking your head out the window
  • Rolling down all the windows
  • Changing the temperature in the vehicle
  • Trying not to stare at division line
  • Driving over rumble strips
  • Listening to stimulating or loud music
  • Taking off shoes or loosening clothing
  • Smoking or chewing tobacco
  • Conversing with someone
  • Rolling head and/or shoulders or other stationary exercise
  • Driving a stick shift
  • Changing driver’s seating position
  • Screaming
  • Playing games in the car

Even one hour less sleep per day than your body needs can impair your ability to function. Take corrective action when you notice:

  • You can't stop yawning.
  • You have trouble keeping your eyes open and focused, especially at stop lights.
  • Your mind wanders or you have disconnected thoughts.
  • You can't remember driving the last few miles.
  • Your driving becomes sloppy – you weave between lanes, tailgate or miss traffic signals.
  • You find yourself hitting the grooves or rumble strips on the side of the road.

What can health workers, employers, and governments do to help reduce the incidence of drowsy driving?

  • Physicians - Can diagnose illnesses that can cause sleepiness, such as SAS and narcolepsy. Medical workers should remind patients about the need for adequate sleep --for good health as well as drowsy-driving prevention.
  • Employers - Employers, unions, and shift-work employees can take measures to reduce sleepiness resulting from shift-work schedules. Countermeasures include following effective strategies for scheduling shift changes and, when shift work precludes normal nighttime sleep, planning a time and an environment to obtain sufficient restorative sleep.
  • Governments - Can raise awareness in the public and policymakers about the purpose and meaning of shoulder rumble strips. Rumble strips, placed on high-speed controlled-access rural roads, alarm or awaken sleepy drivers whose vehicles are going off the road. Rumble strips reduce drive-off-the-road crashes by 30 to 50 percent. They are not by themselves, however, a solution for sleepy drivers, who should take any wake-up alert as a signal to stop driving and get adequate sleep before driving again.

Can education improve driving behaviors in high-risk groups?

A drowsy-driving study conducted by the Harvard University School of Public Health focused on two target populations with high incidence of drowsy driving: young males, and shift workers.

  • Young men - reported sleeping between 5 - 7 hours a night and were aware that drowsiness was a hazard when driving. However, they seemed to accept these risks as part of their lifestyle, and were unwilling to change either their sleep routines or their driving behavior.
  • Shift workers - got less sleep than the young men (4 - 6 hours per day) with sleep often fragmented into 2 distinct periods. Acutely aware of the risks of driving when sleepy, many of them admitted to falling asleep when driving home and not remembering substantial parts of the trip. Shift workers wanted to learn how to improve their sleep and expressed an interest in changing their routine if better sleep would result. Unfortunately outside factors (family and noise) interfered with their ability to get adequate and restful sleep on a regular basis.

Data collected by NHTSA (Bellows Figure) points to a relationship between the time of day and frequency of crashes experienced by drowsy drivers - The risk of a crash related to sleepiness increases during nighttime hours among both younger drivers (25 years of age and younger) and drivers between the ages of 26 and 45. However, younger drivers have no increased risk during the afternoon, when the predictable circadian sleepiness peak is expected. Drivers ages 45 through 65 have fewer nighttime crashes, but peak at 7 a.m. Drivers older than 65 are more likely to have fall-asleep crashes during the mid afternoon.

Fig: Data collected by NHTSA (Figure 3) points to a relationship between the time of day and frequency of crashes experienced by drowsy drivers

Figure: Time of occurrence of crashes in drivers of different ages in which the crashes were attributed by the police to the driver being asleep, and in which alcohol was not judged to be involved. The four panels show plots for drivers of the following ages: (A) drivers 25 years of age or younger; (B) drivers 26 to 45 years of age; (C) drivers 46 to 65 years of age; and (D) drivers older than 65 years. In each panel, the horizontal axis is the time of day and the vertical axis is the number of crashes. However, the scale of the vertical axis is different for each panel. The data are for the years 1990 to 1992, inclusive.

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