Every year at this time, police forces take to the streets in an effort to curb drunk driving. But drowsy drivers pose a risk to road safety, too, as they unwittingly catch up on sleep behind the wheel.

The director of the sleep division at Harvard Medical School, Dr. Charles Czeisler, explains that drivers can often slip into a micro-sleep episode.

"You can be on a highway and you don't remember how you got from point A to point B," Czeisler told CTV's Canada AM in an interview from Boston this week, explaining that the bouts can last up to 15 seconds.

Travelling at 100 kilometres per hour, it takes a vehicle just three seconds to cover the length of a football field. That means just a brief moment of sleep, and the inattention it brings, can have tragic consequences.

In fact, the Canadian Council of Motor Transport Administrators estimates that approximately 20 per cent of fatal collisions involve driver fatigue.

The problem, Czeisler explained, is that drivers can be asleep and not even realize it as their pre-frontal cortex drifts off before the rest of the brain.

"So you still might be able to carry out rudimentary tasks like steering the car, even though you may be missing the parts of the brain responsible for judgment," he said. "And that can lead to the phenomenon called automatic behaviour."

There are warning signs, however, which the New Brunswick Ministry of Public Safety says include:

  • Sore, tired or slowly blinking eyes
  • Frequent yawning
  • Drowsiness, nodding off
  • Slowing reaction time
  • Loss of concentration, boredom, irritability, restlessness
  • Drifting from your lane, inconsistent speed, erratic braking
  • Missed traffic lights, turns or exits

"Nobody falls asleep at the wheel without realizing they're exhausted beforehand," Czeisler said.

That's why drivers typically try one of the tried-but-not-so-true quick fixes.

Drinking coffee, for example. Rolling the windows down or cranking the air conditioner for a face full of bracing air. Even blasting the tunes or simply giving the old head a shake.

They might seem like good ideas, but they're not the way to go.

According to the experts at the Traffic Injury Research Foundation, the best ways to protect yourself against the effects of drowsiness or fatigue behind the wheel include:

  • Getting plenty of rest before the drive
  • Avoiding driving at times you'd usually be asleep
  • Driving during daylight hours, if possible
  • Taking regular breaks during long trips

The only "cure"? Sleep.

And if you can't settle in for a full 8 hours of shut-eye, a more substantial nap of 20 to 40 minutes is typically enough for a temporary rejuvenation.

Let us know in the comments: Have you ever nodded off behind the wheel? What do you do to avoid driving drowsy? Or, what do you do when you're behind the wheel and feel the sandman settling in?