SATURDAY, May 24 (HealthDay News) -- Drowsy driving is one of the reasons why the Memorial Day weekend is one of the deadliest times on American roads, according to the National Sleep Foundation (NSF).

"Too many Americans are too tired to drive. In fact, according to NSF's recently released 2008 Sleep in America poll, an alarming 36 percent of respondents admit to actually nodding off or falling asleep while driving," David M. Cloud, NSF's chief executive officer, said in a prepared statement.

"Hectic weekend getaways may add to the problem as many get on the road at ungodly hours to beat traffic. Not getting enough sleep puts everyone at increased risk for fall-asleep crashes. Understanding crucial warning signs and countermeasures is key to preventing sleep-related crashes," Cloud added.

Being sleepy slows reaction times, impairs vision, delays information processing and causes lapses in judgment -- all of which reduce driving safety.

There are a number of warning signs that you're too tired to continue driving and need to find a safe place to pull over. The signs include:

  • Rolling down the window or turning up the radio.
  • Difficulty focusing, frequent blinking and/or heavy eyelids.
  • Drifting from your lane, swerving, tailgating and/or hitting rumble strips.
  • Trouble remembering the last few miles driven.
  • Missing exits or traffic signs.
  • Trouble keeping your head up and repeated yawning.

The NSF offers the following drowsy-free driving tips to help you arrive safely at your destination:

  • Get a good night's sleep (seven to nine hours) the night before you start your trip.
  • Don't be too rushed to get to your destination. Take a break every two hours or 100 miles.
  • Don't drive alone for long distances. Have a partner who can share the driving duties and help identify warning signs of fatigue.
  • Avoid alcohol and medications (prescription and over-the-counter) that may impair driving abilities and magnify the effects of sleepiness.
  • Don't drive at times when you would normally be sleeping.
  • If you start to feel sleepy while driving, stop at a safe place and take a 15- to 20-minute nap.
  • Pack a cooler with caffeinated beverages or keep caffeinated gum and mints in the glove box. The equivalent of two cups of coffee can increase alertness for several hours. Caffeine in liquid form takes about 20 to 30 minutes to take effect, so consume it before you take a short nap to get the benefits of both.

More information

The U.S. National Highway Traffic Safety Administration has more about traffic safety.