Drowsy Driving: Warning Signs and How to Stay Alert Behind the Wheel

Most drivers know not to drive after drinking.

Far fewer treat a long day, a short night or a late drive home with the same caution.

Yet fatigue quietly slows your reactions, clouds your judgment and can put you to sleep for a few seconds without warning.

This guide explains why drowsy driving is so dangerous, how to recognize the warning signs and what actually helps you stay safe.

How big is the problem?

Drowsy driving is hard to measure, because there is no breath test for sleepiness.

Police reports often miss it, since a driver may not admit it or may not even realize it.

To get a better estimate, the AAA Foundation for Traffic Safety studied in-depth crash investigations from 2017 to 2021.

Its researchers estimated that 17.6 percent of all fatal crashes in that period involved a drowsy driver.

Over those five years, that adds up to an estimated 29,834 people killed in crashes with a drowsy driver.

The same study notes that official police-reported figures are widely regarded as large underestimates of the true problem.

Why sleepiness is so dangerous behind the wheel

Being tired does not only make you want to close your eyes.

It changes how your brain works while you are still awake.

The National Heart, Lung, and Blood Institute explains that sleep-deficient people have slower reaction times and make more mistakes.

They also have more trouble making decisions and solving problems, which is exactly what driving demands every second.

The NHLBI adds that studies show sleep deficiency can harm driving ability as much as or more than being drunk.

Losing sleep also adds up quickly.

Several nights of losing one to two hours of sleep can hurt you as much as a day or two without sleep.

Microsleep: the danger you may not notice

The most frightening effect of fatigue is microsleep.

The NHLBI describes microsleep as brief moments of sleep that happen when you are normally awake.

You cannot control it, and you might not even be aware that it happened.

Have you ever arrived somewhere and not remembered part of the drive?

The NHLBI points to that exact experience as a possible sign of microsleep.

At highway speed, a car covers more than 100 feet every second.

A few seconds of microsleep can carry you across a lane line, off the road or into the back of slowing traffic.

Warning signs that you are too tired to drive

Sleepy drivers often feel able to keep going, even when they are not.

That is why it helps to watch for specific signs instead of trusting how you feel.

Pull over and take a break if you notice any of these:

  • Frequent yawning or rubbing your eyes.
  • Heavy eyelids or trouble keeping your eyes focused.
  • Not remembering the last few miles you drove.
  • Missing an exit, a turn or a traffic sign.
  • Drifting out of your lane or hitting the rumble strip.
  • Following the car ahead too closely without meaning to.
  • Restless, irritable feelings or trouble holding a steady speed.

The NHLBI also lists a simple everyday test.

You might be sleep deficient if you often feel you could doze off while riding in a car for an hour without stopping.

The same goes for sitting in traffic for a few minutes.

Who is most at risk

Anyone can become a drowsy driver, but some situations raise the risk.

  • Young drivers. The AAA Foundation study found the highest share of drowsy drivers among those aged 16 to 20.
  • Late-night and early-morning drivers. The most fatal drowsy crashes happened between 11 pm and 3 am.
  • Drivers before dawn. The share of drowsy drivers was highest in crashes between 3 am and 7 am.
  • Shift workers. Working nights or rotating shifts means sleeping at the wrong time of day.
  • People with untreated sleep disorders. Conditions such as sleep apnea can leave you tired after a full night in bed.
  • Drivers who have been drinking. The AAA Foundation found drowsiness was more common among drivers with alcohol in their blood.

Rural roads deserve special attention too.

The AAA Foundation found the share of drowsy drivers was highest in crashes on rural collectors and local roads.

What does not work

Many drivers rely on quick tricks to push through the last hour.

Turning up the radio, opening a window or blasting cold air may make you feel more awake for a moment.

None of them pay back the sleep your brain is missing.

Caffeine can help a little, but it takes time to kick in and does not remove the risk of microsleep.

The only real cure for sleepiness is sleep.

How to prevent drowsy driving

The best defense starts before you get in the car.

Before the drive

  • Get a full night of sleep before any long drive. The NHLBI notes that adults who regularly get seven to eight hours of sleep have lower health risks.
  • Avoid starting a long trip right after a full work shift.
  • Plan to drive during the hours you are normally awake.
  • Check the labels on any medicine you take for warnings about drowsiness.
  • If you are often sleepy during the day, talk to a doctor about a possible sleep disorder.

During the drive

  • Plan a break every two hours or about every 100 miles, even if you feel fine.
  • Share the driving with a passenger who is rested and able to take over.
  • Ask a passenger to stay awake and talk with you, especially at night.
  • Eat light meals, since a heavy meal can make you sleepier.
  • Do not drink alcohol before or during the trip.

What to do when you feel drowsy

When the warning signs appear, treat them as a signal to stop, not to push harder.

  1. Leave the highway at the next exit or pull into a rest area.
  2. Park in a safe, well-lit place away from traffic.
  3. Lock the doors and take a short nap of 15 to 20 minutes.
  4. Walk around and stretch for a few minutes after you wake up.
  5. If you still feel sleepy, stay longer or find a place to spend the night.

Never stop on the shoulder of a busy highway just to rest.

A parked car on the shoulder can be hit by another tired or distracted driver.

If you are close to home and badly tired, it is better to call someone for a ride.

Arriving an hour late is a small price compared with a crash.

The bottom line

Drowsy driving is common, hard to detect and far more dangerous than many drivers believe.

Fatigue slows your reactions and can cause microsleep that you may never notice.

Know the warning signs, plan your sleep and breaks before long drives, and stop as soon as you feel sleepy.

No meeting, deadline or arrival time is worth falling asleep at the wheel.

Sources and Further Reading