Driving Tired vs. Driving Impaired: Which is Worse?


driving and daytime sleepiness

Have you ever gotten behind the wheel of your car when you’re yawning and drowsy? Many people have, thinking it’s not that big a deal. After all, it’s not like you’re driving while drunk, right?

Actually, driving while tired is closer to driving while chemically impaired than you might think. Driving while drowsy makes you less aware of what’s going on around you, it affects your ability to make decisions and take actions when needed, and it slows your reaction time.

Take a look at just how risky driving while tired can be — and see what you can do to avoid these dangers.

Driving Tired vs. Driving Impaired

The effects of driving while drowsy — slowed reaction time, impaired decision making and so on — sound suspiciously like the results of driving drunk. That’s because the effects of driving impaired are remarkably similar to those of driving drowsy… and just as dangerous.

Drunk driving and drowsy driving reach the same end result through slightly different means. Drunk drivers often experience problems with depth perception, the ability to discern speed and clear eyesight. They may exhibit risky driving as they lose their inhibitions, and they’re typically overconfident about their ability to drive.

Drowsy drivers, on the other hand, don’t show these changes. Instead, they become unable to stay vigilant. In both types of impaired driving, the ability to respond quickly and appropriately is hindered, with slowed responses leading to crashes.

Drowsy Driving Facts and Statistics

Drivers who have been awake for 18 hours show physical effects that are comparable to those of people with a blood alcohol content of 0.05%. Only two more hours of sleeplessness pushes the BAC equivalent to 0.08%, which is the common legal limit for drunk driving across the United States. And when a driver has been awake 24 hours, their physical state is that of someone with a BAC of 0.1%. The reactions of both drunk and drowsy drivers show up in impaired hand-eye coordination, inability to multitask and slower reaction time.

The results also show up in accident statistics. According to a study in France, both drunk driving and sleep-impaired driving double the chances of being in an accident. That danger doesn’t require staying up all night, either. Even mild sleep deprivation impairs the ability to drive. If you sleep six to seven hours a night, which seems moderate to many people, your risk of being in an accident is doubled. If you only sleep five hours, the risk is quadrupled.

The Dangers of Driving While Drowsy

The National Highway Traffic Safety Administration reports that drowsy driving is responsible for at least 91,000 car accidents per year. Those numbers may, in fact, be low since there’s no scientific measurement for drowsy driving, as there is for drunk driving, and many people don’t want to admit they fell asleep at the wheel.

The Centers for Disease Control and Prevention estimates that between 15% and 33% of fatal accidents are caused by drowsy driving. With up to 40% of drivers admitting to having fallen asleep at the wheel, it’s clear that driving while tired is not a rare occurrence.

Drowsy drivers often have difficulties maintaining an appropriate speed for road conditions, and they tend to drive too close to other vehicles. Given their impaired reaction times, this means they’re unlikely to respond quickly enough to avoid accidents. In addition, they often end up weaving between lanes, sometimes at high speed, and they may cause single-driver accidents by driving right off the road.

Some drowsy drivers become aware of their pending impairment as they find themselves yawning, drifting over lane markers and startling to wakefulness as they realize their eyes closed for a second or two. Others, however, simply fall asleep with no warning signs.

Risky Situations for Driving Drowsy

Certain times of the day and some road conditions make people more prone to drowsy driving. As you might expect, driving tired most often occurs in the wee hours between midnight and 6 a.m., but it may surprise you to learn that late afternoon is also prime time for drowsy driving. Driving on a straight, boring road intensifies the condition, as does driving alone.

Drivers who are prone to drowsy driving include:

  • Young, inexperienced drivers
  • Professional drivers who are on the road for excessive periods
  • Drivers who have recently consumed alcohol or drugs
  • Drivers taking sleep-inducing medications
  • Night shift workers
  • People who have slept fewer than six hours recently
  • People with sleep apnea and other sleep disorders

In fact, people with sleep apnea are five times more likely to be in an auto accident than those without the condition. The sleep condition, which involves difficulty breathing while sleeping, leads to chronic fatigue and sleepiness. As a result, fully 80% of truly terrible car accidents, including head-on collisions and accidents involving pedestrians, are linked to drivers with sleep apnea.

Tips for Staying Safe on the Road — and What Doesn’t Work

It’s important to pay attention to the signs warning you that you may be too tired to drive safely. Among these signs are:

  • Realizing you don’t remember driving the last few miles
  • Drifting into another lane
  • Yawning
  • Tailgating the car in front of you
  • Irritable or aggressive driving
  • Frequent blinking or sagging eyelids
  • Difficulty focusing
  • A drooping head
  • Missing exits or road signs
  • Hitting the rumble strip or the lane divider dots

As soon as you experience any of these warning signs, take immediate action. Pull over, find a safe place and take a brief nap.

Here’s what doesn’t work if you find yourself driving while sleepy:

  • Caffeine
  • Turning up the radio extra loud
  • Opening the window or vents to let cold air blow on you

You can plan in advance for long drives or drives at times when you tend to get sleepy. Drive with a buddy who can take turns behind the wheel. Take a break every hour or two, and get out and walk around. Avoid alcohol and other controlled substances completely when you know you have to drive and time any required medications so they’re less likely to affect your driving.

And most important: get enough sleep. If you have sleep apnea, use your CPAP machine regularly to minimize symptoms and keep you safe behind the wheel. By taking these proactive steps, you can protect your own safety and that of everyone around you.

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