Does marijuana lead to hazardous driving?
AAA seems to think so.
The organization is calling attention to its new report out of Washington State, which legalized recreational use of marijuana 3½ years ago.
Two years after that state legalized marijuana in November 2012, 17 percent of drivers in fatal crashes there tested positive for marijuana use, according to the AAA Foundation for Traffic Safety.
That figure was up from 8 percent in 2013.
“Of all the fatal crashes in the state, the proportion that involved a driver that had recently consumed marijuana more than doubled in one year,” Jake Nelson, AAA’s director of traffic safety and advocacy, told the Washington Post. “That doesn’t say that people who had smoked marijuana and got behind the wheel were responsible for an increase in fatal crashes. It means that recent marijuana use is a growing contributing factor in traffic crashes that kill people.”
AAA officials said the issue is important because at least 20 states are considering some form of marijuana legalization this year. There are two bills to legalize recreational use of marijuana in the New York State Legislature, according to the organization. With what it calls arbitrary testing in place in some states, the public is at risk of seeing unsafe motorists go free and others being wrongfully convicted, officials said.
Authors of the AAA study, released last week, looked at fatal crashes from 2010 through 2014, the most recent year for which data was available. The data consisted of a total of 2,070 crashes and 3,031 drivers. More than a third of the drivers in those crashes weren’t tested for any drugs, and researchers estimated use for cases where there was no data through a statistical technique known as “multiple imputation.”
Of the drivers who had tetrahydrocannabinol (THC) – marijuana’s active ingredient – in their blood, 39 percent also had alcohol in their blood. More than 10 percent of drivers who had THC also had alcohol and one or more other drugs in their systems.
Because of the speed at which the body metabolizes THC and the amount of time that passes before tests are taken, among other factors, authors of the research believe they may be underestimating the proportion of drivers in fatal crashes who had marijuana in their system.
The foundation released a second report indicating that in states where a specific legal limit has been set for marijuana’s active ingredient in a driver’s blood, such measures aren’t supported by science and are not accurately testing whether a driver is impaired. Higher levels of THC in one person may not make them impaired, while a lower level in another driver might make them unsafe behind the wheel, researchers said.
That’s different from alcohol levels, in which a greater amount in the blood increases the risk of being involved in a crash, researchers said.
The work supports previous research that THC levels do not adequately reflect impairment.
Researchers recommend moving away from legal limits for THC and instead training officers to be certified drug recognition experts.
Finding that more drivers have marijuana in their system in a state that had legalized the substance is far from surprising, said Jolene Forman, attorney with the Drug Policy Alliance, a New York City-based organization with offices across the country calling for reforming marijuana laws.
The alliance agrees that setting a true blood-test threshold is not possible, Forman said.
Research findings are inconsistent on the extent to which marijuana use impairs drivers, she said. Other studies have found a higher risk for crashes associated with tuning the radio or driving with multiple passengers than testing positive for THC, she added.
Mothers Against Drunk Driving, an advocacy group for victims of drunken and drugged driving, “supports more widespread training and certification of drug recognition experts” but does not take a position on the legalization of medicinal or recreational marijuana, according to its website.