Are drowsy drivers as dangerous as drunk drivers?

On Behalf of | Dec 21, 2021 | Motor Vehicle Accidents

Fatigued driving doesn’t get as much press as drunk driving, but it could be just as dangerous and might be more common. Some experts believe that drowsiness may be involved in as many as 21% of all fatal motor vehicle accidents, or more than 6,000 every year.

By contrast, according to the National Highway Traffic Safety Administration (NHTSA), drunk drivers were responsible for nearly 30% of fatal crashes in 2017, or 9,949 recorded fatalities.

However, it’s important to note that alcohol impairment is relatively easy for police to spot and write down in their reports. Drowsiness tends to dissipate with the surge of adrenaline people often experience in a crash, so it’s much less likely to show up on a police report. As a result, many experts believe that drowsy driving is highly under-reported as a cause of traffic crashes.

How do the symptoms of fatigue compare to drunkenness?

Although the two states are not identical, they do have a lot in common. Both tend to slow the driver’s reaction time, reduce their alertness and affect their decision-making. In controlled studies, researchers have found that those who were drunk and those who were drowsy got into similar numbers of crashes.

There are some differences, too. Drunkenness can affect your eyesight and depth perception, which can make it harder to gauge another vehicle’s speed. Drunk drivers tend to be impulsive, uninhibited and too confident. By contrast, drowsiness tends to inhibit the kind of vigilance and speedy reaction time that prevents crashes.

According to research, being awake for 18 hours has about the same effect on reaction times, vigilance and hand-eye coordination that a blood alcohol content of 0.05% — enough to impair a driver. And 18 hours isn’t a shockingly long time to be awake.

Once a person has been awake for 20 hours, they drive like someone with a blood alcohol content of 0.08%, the legal limit in most states.

After 24 hours awake, a driver is impaired approximately as much as someone with a blood alcohol content of 0.10%, which is significantly drunk.

One study by the AAA Foundation for Traffic Safety discovered that people who had slept between six and seven hours a night were at double the risk of a crash as those who slept eight hours or more. Sleeping less than 5 hours in a night doubled the risk again.

Professional drivers are at elevated risk of drowsy driving

While anyone might get behind the wheel while they’re too tired to drive safely, certain people are more likely than others to drive while drowsy:

  • Professional drivers, who are often under substantial time pressure and who may drive for many hours without significant rest
  • People with sleep disorders such as sleep apnea
  • People taking certain medications that make them sleepy
  • Shift workers
  • Young people

Anyone who drives while they’re sleepy could be dangerous, but a drowsy professional driver could cause a catastrophic crash.

How to spot a drowsy driver

It may be difficult to spot someone who’s falling asleep behind the wheel, but here are a few signs to watch out for:

  • Drifting between lanes or hitting the rumble strips on the side of the road
  • Speeding up and slowing down
  • Following other drivers too closely
  • Visible yawning or drooping head
  • Aggressive driving tactics

We can’t prevent every accident. Sometimes, impaired, drowsy, distracted or bad drivers can’t be completely avoided. All we can do is drive defensively and be vigilant for hazardous drivers.


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