An official website of the United States government.
Marijuana Use and Highway Safety
A growing number of Americans report that they use marijuana. Most states now allow the use of marijuana for treatment of medical conditions. Ten states and the District of Columbia, representing a quarter of the U.S. population, have decriminalized the recreational use of marijuana, and other states are considering following suit.
As the opportunity for legal use of marijuana grows, there is concern about the impact of marijuana usage on highway safety. In a 2018 survey, the majority of state highway safety officers considered drugged driving an issue at least as important as driving while impaired by alcohol (which is associated with over 10,000 highway deaths each year). As of May 2019, 18 states have enacted laws declaring that a specified concentration of THC in a driver’s body constitutes evidence of impairment and is inherently illegal (referred to as per se laws), similar to the .08% blood alcohol content (BAC) standard of alcohol impairment.