AUGUSTA — An effort to establish a legal standard for operating under the influence of marijuana has stalled in the Legislature, but another proposal could come with input from advocates by next year.

It’s already prohibited in Maine to be under the influence of marijuana and other drugs while driving, but unlike the law on alcohol, there’s no legal limit that indicates intoxication.

A bill backed this year by Maine Secretary of State Matthew Dunlap would have set a blood intoxication level of 5 parts per billion of tetrahydrocannabinol, or THC, marijuana’s psychoactive ingredient. But that part was stripped by the Legislature’s Transportation Committee and sent to the Criminal Justice and Public Safety Committee, which voted Tuesday to recommend that Dunlap’s office convene a working group to study the issue before possibly returning with another proposal by 2016.

Dunlap said he’ll be “happy to do it,” and his office will examine the issue. However, an expert who addressed the Maine Impaired Driving Summit in April said science is inconclusive on a level of THC indicating impairment, that states are “setting these numbers somewhat arbitrarily” and Maine’s current law could be strong enough.

Advocates also have been wary of it, but Paul McCarrier, president of Legalize Maine, a pro-marijuana legalization group, said he’d be willing to work with the state on a new proposal.

“We’re not against setting a limit. We just want the science to support that,” he said.

Medical marijuana is legal in Maine, and in 2016 voters could be asked to decide on dueling proposals to legalize recreational marijuana, which only Colorado, Washington and Alaska have done so far.

Six states have set THC blood intoxication levels, but of the 23 medical marijuana states, Maine is one of 12 where convictions must be proved through a totality of evidence, including blood tests, erratic driving and sobriety test results, according to the Marijuana Policy Project. Colorado, Washington and Montana have set them at the level that Maine considered this year.

“Really, the numbers are where the debate’s been and where it’s going to be,” Dunlap said.

In Maine, there were 3,600 convictions for operating under the influence of alcohol in 2014 alone, but from 2004 to 2014, just 3,250 drivers were evaluated by the state’s drug recognition experts, according to data provided by Maine State Police Trooper Aaron Turcotte, a recognition expert. Of those, 1,400 had marijuana in their system.

Michael Shepherd — 370-7652

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Twitter: @mikeshepherdme