Alcohol Impaired Driving Facts

Risk Factors for Increased Alcohol Consumption

Risk Factors for Alcohol Impaired Driving

Risk and Protective Factors

Marijuana and Driving Facts

Traffic Safety and Impaired Driving Facts

Marijuana and Driving

Most times when people think of impaired driving, only alcohol comes to mind. Some students believe that drivers are just fine (or even more careful than normal and surely much better than while drunk) to drive when they're high, right? Wrong - try again! Here's the raw data that serves as proof that there are serious effects of driving stoned and that it needs to be taken as a very serious issue.

  • Marijuana limits learning, memory, perception, judgment, coordination, reaction time, concentration and complex motor skills, like those needed to drive a vehicle. These effects can last up to 24 hours after smoking marijuana. 1

  • In addition to alcohol, drugs cause a serious highway safety problem. Drugs are estimated to be used by approximately 10-22% of drivers involved in crashes, often in combination with alcohol. 1

  • In 2002, between 13 and 18 percent of young drivers aged 17 to 21 reported driving under the influence of an illicit drug during the past year. 2

  • A roadside study of reckless drivers (not under the influence of alcohol) showed that one in three tested positive for marijuana and an additional 18 percent tested positive for marijuana and cocaine. 2

  • A study of patients in a shock-trauma unit who had been in collisions revealed that 15 percent of those who had been driving a car or motorcycle had been smoking marijuana and another 17 percent had both THC (the psychoactive chemical causes the "high" and impairment) and alcohol in their blood. 2

  • In an ongoing study of non-fatally injured drivers, 23.5% of those drivers under 21 tested positive for drugs other than alcohol. 1

  • While alcohol is the predominant substance in fatal crashes, marijuana is the second most frequently found substance in crash-involved drivers, according to a NHTSA study. Alcohol and marijuana are also frequently found together, which results in a dramatic decrease in driving performance and spike in impairment levels. 2

  • Marijuana, even in low to moderate doses, negatively affects driving performance, such as the ability to avoid collisions with evasive action. The effect of combining moderate doses of alcohol and moderate doses of marijuana resulted in a dramatic decrease in driving performance and increased the level of impairment from a .04 BAC (alcohol alone) to impairment comparable to up to 0.14 BAC (alcohol and marijuana combined). 2


1. National Highway Traffic Safety Administration. Drug Impaired Driving. Retrieved on October 28, 2003, from the World Wide Web:

2. Office of National Drug Control Policy. Marijuana and Kids: Steer Clear of Pot Fact Sheet. Retrieved on November 25, 2003, from the World Wide Web:

Note: We are updating our statistical information to provide you the most accurate data for your impaired driving prevention efforts. New data will be available on this site in August 2013. In the meanwhile, you can check information from the National Highway Traffic Safety Administration (NHTSA).