Nationally, drug-related traffic crashes now surpass alcohol-related crashes. In 2016, among drivers tested in fatal crashes, 44% had used a legal or illegal drug, compared with 38% who tested positive for alcohol.

Even if medications are legal and prescribed or recommended by a clinician, some can impair cognition and motor skills necessary for safe driving. Substances include marijuana, prescription drugs, and over-the-counter medications such as cough suppressants, antihistamines, and sleep aids.

In 2013–2014, the National Highway Traffic Safety Administration’s National Roadside Survey of Alcohol and Drug Use by Drivers found drugs in 20% of all drivers on weekend nights.

Marijuana
Marijuana use is increasing nationally. According to a 2014 survey conducted by the CDC, there were 7,000 new marijuana users per day. This increase may be due to the changing legal landscape regarding marijuana use. The increase in drug-related driving deaths coincided with marijuana legalization in some states.

After alcohol, marijuana is the most common drug found in drivers killed in drug-related crashes. In 2016, of the 44% of drivers killed in crashes who tested positive for drugs, 41% had used some form of marijuana.

Opioids
An especially dangerous upward trend in the misuse of prescription drugs has become known as the “U.S. opioid epidemic.”  Prescription opioids are potent pain medications that can affect driving by causing drowsiness and impairing cognitive function. Prescriptions for drugs such as oxycodone (OxyContin), hydrocodone (Vicodin), and morphine have quadrupled from 76 million in 1991 to nearly 300 million in 2014. In 2016, 19% of drivers killed in crashes who tested positive for drugs tested positive for some opioid.