Easing of marijuana laws worries road safety advocates

As the nation eases marijuana laws, road safety advocates worry that highway rules for driving under the influence of pot are lagging, which could lead to fatal crashes.

Medical marijuana is legal in 23 states and Washington, D.C.; adult recreational use is legal in Washington state and Colorado; marijuana has been decriminalized in 16 states and Washington, D.C..

"I'm very concerned, because I feel that we're painting the plane as we're flying it," says Jake Nelson, director of traffic safety, advocacy and research for AAA. "When we were at this stage of the game with alcohol, starting to pass laws, we knew a lot more about how alcohol affected driving performance, crash risks and how that changed with different concentrations of alcohol in a person's body."

The research is mixed on how cannabis affects driving performance. Though marijuana can slow decision-making and decrease peripheral vision, drivers under the influence of marijuana tend to drive more slowly and less aggressively, says Jonathan Adkins, executive director of the Governors Highway Safety Association.

"But if you mix it with alcohol, it has a stimulative effect," he says. "It makes reckless drivers. It makes drivers take a lot of chances. That's the biggest concern."

The National Highway Traffic Safety Administration, the nation's primary road safety agency, says its Roadside Survey of drivers in 2007 found that 8.6% had marijuana in their system. The NHTSA is researching how state legalization of cannabis impacts the prevalence of marijuana use by drivers. It's also completing the first study of the crash risk of drivers using drugs compared with those who have no drugs in their system.

"The legalization of marijuana under state laws poses new concerns, and NHTSA has research underway to understand the effects of drugs other than alcohol on safe driving and their role in crashes," the agency said in a statement.

Adkins says the nation is putting the cart before the horse. "Traffic safety isn't even being considered in the cities and states that are considering legalization," he says. "It isn't even being considered until after the fact."

Transportation officials in Colorado, where retail marijuana sales started in January, and in Washington, where sales began in July, said they don't have any data on whether there have been any upticks in pot-related crashes, injuries or fatalities.

A study published in January in the American Journal of Epidemiology found that fatal crashes involving marijuana use tripled during the previous decade.

Researchers from Columbia University's Mailman School of Public Health studied fatal crash statistics from six states; they found that marijuana as a factor in fatal crashes rose from 4% in 1999 to 12% in 2010. Drugged driving overall rose from 16% of fatal crashes in 1999 to 28% in 2010.

The study authors found that combining alcohol and marijuana significantly increases a driver's risk of death. A driver under the influence of alcohol is 13 times more likely to be in a fatal crash than a sober driver; a driver under the influence of alcohol and marijuana is 24 times more likely to die in a crash than a sober driver.

The authors noted that, because traces of marijuana can be detected in the blood up to a week after use, their findings on marijuana indicate use but not necessarily impairment.

In August, New York teenager Joseph Beer was sentenced to five to 15 years in prison for a marijuana-involved crash that killed four of his friends. Beer was 17 in October 2012 when he smoked marijuana, then drove his Subaru Impreza at speeds exceeding 100 mph before crashing into a tree on the Southern State Parkway.

All five people in the vehicle were ejected; Beer was the only survivor. He pleaded guilty to aggravated vehicular homicide and driving under the influence of marijuana.

The trend toward liberalization of pot laws is rolling on: Alaska, Oregon and Washington, D.C., have November ballot measures to legalize adult recreational use; Florida has a ballot measure to legalize medical marijuana, according to the National Conference of State Legislatures. On Sept. 18, Philadelphia became the latest city to decriminalize marijuana.

Six states – Colorado, Montana, Nevada, Ohio, Washington and Pennsylvania – have enacted laws or established codes setting a specific driving threshold for the amount of THC, the primary psychoactive ingredient in cannabis, in the blood, the NCSL says. Drivers in excess of those thresholds could face a charge of driving under the influence of marijuana.

Similar to the .08 blood-alcohol content threshold for driving under the influence, the threshold is set at a blood content of 5 nanograms per milliliter of blood in Colorado, Montana, Washington and Pennsylvania and at 2 nanograms in Nevada and Ohio, says Anne Tiegen, a transportation analyst at the NCSL. This year, Alabama, California, New Mexico and Pennsylvania (where the threshold is established by the state Health Department as a guideline) considered but did not pass statutes setting a threshold, Tiegen says.

Advocates say those thresholds are arbitrary, partly because they establish only the presence of THC in a person's body without determining how impaired they are.

"We know almost nothing about how (pot) affects driver performance at different concentrations in people's bodies," Nelson says. "Does it matter if you consume a lot or a little? How quickly does the substance dissipate or break down in the body? We don't know anything that we would like to know before we start to pass laws."

Road safety advocates generally agree that one of the key ways for law enforcement to combat drug-impaired driving is with drug recognition experts, specially trained police officers who can take a suspected drugged driver through a series of screens at roadside to narrow down the class of drug that is most likely impairing the driver.

The number of drug recognition experts varies widely from state to state: from more than 1,200 in California to two in Virginia, Nelson says.

Because there are so few of them in some states, by the time one arrives at a traffic stop, the active THC might have completely left a suspected drugged driver's body, Nelson says.

"There really isn't a standard in place for what constitutes impairment from using marijuana," says John Bowman of the National Motorists Association.