Driving Under the Influence, of Marijuana

This article explores some of the changes in traffic law enforcement, particularly identifying driving under the influence (DUI), as marijuana use becomes legal and more widespread. The author notes that, while the standard roadside tests for alcohol use (drunk driving) will identify nearly 90% of impaired drivers, the same is not true for identifying drivers under the influence of marijuana. The article focuses on scientific research in three areas: how dangerous DUI from marijuana is, how to test drivers for impairment, and how the risks compare to driving drunk. Evidence is accumulating that marijuana use causes deficits that affect driving ability, approximately a twofold increase in the risk of an accident if there is any measurable amount of THC in the bloodstream. However, this compares to risks from drunken driving of up to a 20-fold increase in the risk of a fatal accident in young drivers, and a ninefold risk in older drivers (up to age 34). The author also reports on various blood and urine tests that can be used to measure the level of THC. The article concludes with a recommendation to focus public resources on combating drunken driving, particularly that which includes mixing marijuana and alcohol.