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Has a patrol officer ever pulled you over for a DWT—driving while tired? European researchers tell us that driving under the influence of fatigue can be just as hazardous for you and other people on the road as driving under the influence of alcohol.

Driving While Tired Just as Dangerous as Driving While Intoxicated

Scientists at the University of Utrecht in the Netherlands and the Université Bordeaux in France concluded that driving for as little as two hours at night was like driving after having two to three drinks.

The researchers had 14 drivers aged 21 to 25 drive either from 3 a.m. to 5 a.m., from 1 a.m. to 5 a.m., or from 9 p.m. to 5 a.m. They were instructed to drive a constant speed of 130 kilometers per hour (80 miles per hour) while staying in the middle of their assigned lane. The researchers monitored their driving to see how often they crossed the center line.

Two hours of driving at night was like driving with a blood alcohol content of 0.05 per cent. Three hours behind the wheel at night was like driving with a blood alcohol content of 0.08 per cent, which is considered "legally drunk" in much of the United States. Driving for 4-1/2 hours during the night was like driving with a blood alcohol level of 0.10 per cent, even more dangerous on the road. Turning up the stereo or cracking the window to let cold air stream in had no effect on driving performance.

Drivers Who Taking Sleeping Pills Are Also Dangerous on the Road

Another group of Dutch researchers looked at the question of whether taking medication to be able to sleep at night made driving more dangerous during the day. The researchers discovered that when drivers took their sleeping pills made all the difference.

Drivers who took zolpidem (marketed as Ambien or Edluar) weren't drowsy during the day if they took the medication just before their normal bedtime. Drivers who waited until the middle of the night to take their sleeping pills, however, had significantly impaired driving ability, and the more they took, the worse they drove.

Tranquilizers in benzodiazepam class, such as Librium (chlordiazepoxide) and Valium (diazepam), almost always cause daytime drowsiness that can affect driving safety, as can the herbal sleep aid kava. However, the effects of the newer sleep aid Sonata (zaleplon), wore off four hours after the pill was taken.

Researchers funded by the European Union recommended that laws be passed to limit nighttime driving to just two hours per night, but these laws would be difficult to enforce, and would greatly complicate schedules for ambulance drivers and the truckers who are permitted to drive at night. In the United States, the FDA has warned that "almost all" sleeping pills can cause problems that are almost as bad as sleep-deprived driving, and in some cases, sleep-driving, which is getting behind the wheel of a vehicle at night with no memory of having done so.

The FDA has ordered American drug companies to pay for studies of Ambien, Butisol sodium, Carbrital, Dalmane, Doral, Halcion, Lunesta, Placidyl, Prosom, Restoril, Rozerem, Seconal, and Sonata. As of early 2011, no new American rules for nighttime driving have been proposed, but doctors already must warn their patients of driving dangers when they prescribe sleeping pills, and states may soon attempt to limit the hours drivers can be behind the wheel at night.
What can you do in the meantime? The Dutch scientists involved in the night driving study also found that the energy drink Red Bull helps sleep-deprived drivers drive more safely at night.  The effects of Red Bull "kick in" about three hours after you drink it. It may not be reasonable, however, to take both Red Bull and a sleeping pill.

  • Mets MA, Ketzer S, Blom C, van Gerven MH, van Willigenburg GM, Olivier B, Verster JC. Positive effects of Red Bull® Energy Drink on driving performance during prolonged driving. Psychopharmacology (Berl). 2010 Nov 10. [Epub ahead of print]
  • Verster JC, Taillard J, Sagaspe P, Olivier B, Philip P. Prolonged nocturnal driving can be as dangerous as severe alcohol-impaired driving. J Sleep Res. 2011 Jan 12. doi: 10.1111/j.1365-2869.2010.00901.x. [Epub ahead of print]
  • Photo courtesy of Krug6on Flickr: