The effects of specific drugs differ depending on how they act in the brain. For example, marijuana can slow reaction time, impair judgment of time and distance, and decrease coordination. Drivers who have used cocaine or methamphetamine can be aggressive and reckless when driving. Certain kinds of sedatives, called benzodiazepines, can cause dizziness and drowsiness. All of these impairments can lead to vehicle crashes.
Research studies have shown negative effects of marijuana on drivers, including an increase in lane weaving, poor reaction time, and altered attention to the road. Use of alcohol with marijuana made drivers more impaired, causing even more lane weaving.
It is difficult to determine how specific drugs affect driving because people tend to mix various substances, including alcohol. But we do know that even small amounts of some drugs can have a measurable effect. As a result, some states have zero-tolerance laws for drugged driving. This means a person can face charges for driving under the influence (DUI) if there is any amount of drug in the blood or urine. It's important to note that many states are waiting for research to better define blood levels that indicate impairment, such as those they use with alcohol.
FACT: An estimated 32% of fatal car crashes involve an intoxicated driver or pedestrian. (NHTSA)
FACT: 3,952 fatally injured drivers tested positive for drug involvement. (FARS)
FACT: Over 1.2 million drivers were arrested in 2011 for driving under the influence of alcohol or narcotics. (FBI)
FACT: Car crashes are the leading cause of death for teens, and about a quarter of those crashes involve an underage drinking driver. (SAMHSA)
FACT: On average, two in three people will be involved in a drunk driving crash in their lifetime. (NHTSA)
Alcohol, drugs and driving simply do not go together. Driving requires a person’s attentiveness and the ability to make quick decisions on the road, to react to changes in the environment and execute specific, often difficult maneuvers behind the wheel. When drinking alcohol, using drugs, or being distracted for any reason, driving becomes dangerous – and potentially lethal!
Sources: National Council on Alcoholism and Drug Dependence, Inc., 2015; National Institute on Drug Abuse, 2016