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Law Enforcement Express Concern About Impaired Driving Due to Marijuana

As Maine voters consider legalizing recreational marijuana through a ballot initiative this fall, highway safety officials are concerned about drug-impaired driving. AAA of Northern New England and the Maine Bureau of Highway Safety hosted a summit on the issue in Portland today. Researchers and experts say policy makers and law enforcement don't have the tools they need to address drug-impaired driving.

Colonel Robert Williams of the Maine State Police says he's having deja vu. Back in the 1980s Maine was facing a crisis with drivers operating under the influence of alcohol. Today, he says, it's the same issue — only with drugs.

"Last year, 47 percent of the fatals involved people who were under the influence. There were 1,331 alcohol-related crashes in Maine, and we can't begin to figure out how many drug-impaired crashes there were."

But the Maine Bureau of Highway Safety says it's an increasingly common factor. And the director of research at AAA, Jake Nelson, says he's troubled by what he sees in other states. A recent AAA report, he says, found that after Washington state legalized recreational marijuana "the proportion of fatal crashes that involved a driver who had recently used marijuana more than doubled in just that twelve month period."

Nelson expects to see a similar trend in other states that legalize marijuana. The problem for law enforcement and policymakers, he says, is that it's difficult to measure impairment from marijuana. Another AAA study looked at data from about a dozen states to try to find a correlation between the amount of THC in a person's blood stream — the primary ingredient in marijuana — and the likelihood of auto crashes.

"No matter how hard we looked, we couldn't find any reliable correlation between how much active THC you have in your body and whether or not you're going to be impaired, and to what degree," he says. "Which means there's no number we can use to reliably predict impairment."

Even so, Nelson says, states like Washington have arbitrarily adopted a legal limit for marijuana at 5 nanograms per milliliter of blood. University of Florida toxicologist Bruce Goldberger says that means some impaired drivers involved in crashes could go free.

"My opinion is the per se limit used in Washington and Colorado is too high. Because in acute users of cannabis, if you don't draw the blood right away after an incident, their blood level will be well below a five."

While highway safety officials and law enforcement are concerned about the challenges of identifying drug- impaired drivers, David Boyer of the Campaign to Regulate Marijuana Like Alcohol says it's all the more reason to regulate the drug, and give consumers more information about it.

"So that adults who choose to use a substance safer than alcohol can see how much THC is in a strain they're purchasing."

Until more research is done on testing for THC levels, AAA suggests that law enforcement use a two-pronged approach: train officers to recognize the signs and symptoms of drug impairment, and test drivers involved in an auto accidents for any positive presence of drugs. Coupled together, it would likely provide enough evidence to hold impaired drivers accountable for vehicle accidents.