Most people are aware of the hazards of drunk driving. But driving while sleepy can be just as dangerous. Indeed, crashes due to sleepy drivers are as deadly as those due to drivers impaired by alcohol. And you don’t have to be asleep at the wheel to put yourself and others in danger. Both alcohol and a lack of sleep hamper your ability to react quickly to a suddenly braking car, a sharp curve in the road, or other situations that require rapid responses. Just a few seconds’ delay in reaction time can be a life-or-death matter when driving. When people who lack sleep are tested by using a driving simulator, they perform as badly or worse than those who are drunk. The combination of alcohol and lack of sleep can be especially dangerous.

Of course, driving is also hazardous if you fall asleep at the wheel, which happens surprisingly often. One-quarter of the drivers surveyed in New York State reported they had fallen asleep at the wheel at some time. Often, people briefly nod off at the wheel without being aware of it—they just can’t recall what happened over the previous few seconds or longer. And people who lack sleep are more apt to take risks and make poor judgments, which can also boost their chances of getting in a car crash.

Here are some potentially life-saving tips for avoiding drowsy driving:

• Be well rested before hitting the road. If you have several nights in a row of fewer than 7–8 hours of sleep, your reaction time slows. Restoring that reaction time to normal often takes more than 1 night of good sleep, because your sleep debt accumulates after each night you lose sleep. It may take several nights of being well rested to repay that sleep debt and ensure that you are ready for driving on a long road trip.
• Avoid driving between midnight and 7 a.m. Unless you are accustomed to being awake then, this period of time is when we are naturally the most tired.
• Don’t drive alone. A companion who can keep you engaged in conversation might help you stay awake while driving.
• Schedule frequent breaks on long road trips. If you feel sleepy while driving, pull off the road and take a nap for 15–20 minutes.
• Don’t drink alcohol. Just one beer when you are sleep deprived will affect you as much as two or three beers when you are well rested.
• Don’t count on caffeine. Although drinking a cola or a cup of coffee might help keep you awake for a short time, it won’t overcome excessive sleepiness or relieve a sleep debt.

Opening a window or turning up the radio won’t help you stay awake while driving. Be aware of these warning signs that you are too sleepy to drive safely: trouble keeping your eyes focused, continual yawning, or being unable to recall driving the last few miles. Remember, if you are short on sleep, stay out of the driver’s seat!