The LePage administration is proposing a bill to establish an official blood-level limit to determine when someone is driving under the influence of marijuana, positioning Maine to be among the first handful of states to adopt such a stoned-driving law.

The idea pleases some members of law enforcement who say they need a clear standard to prevent drugged driving. Maine legalization advocates say they don’t condone driving under the influence either, but that such a test is not based on sound science.

The bill, which is being prepared by the Department of Public Safety, is one of several marijuana-related proposals that lawmakers will consider as legalization advocates continue to push for a statewide vote in 2016 to allow recreational use of marijuana in Maine. Other proposals include a perennial bill to legalize and tax marijuana for recreational use, as well as bills to eliminate the list of qualifying conditions for medical use and to protect patient privacy in the state’s medical marijuana program.

Maine’s law against operating under the influence – OUI – already prohibits driving a motor vehicle while impaired by marijuana, but there is no specific breath or blood-level limit as there is with alcohol.

The push to pass a marijuana OUI bill in Maine comes as the Office of National Drug Control Policy is taking steps to reduce drugged driving across the country and encouraging states that have approved medical or recreational marijuana use to adopt drug impairment laws. Details of the marijuana OUI bill have not been released and department officials declined to talk about it until the final bill language is set. However, the title – An Act to Establish a Marijuana Chemical Test Level to Determine Whether a Motor Vehicle Operator is Operating Under the Influence of Marijuana – clearly indicates the intent of the bill.

So far, six other states have set legal limits for the concentration of tetrahydrocannabinol – or THC, the psychoactive ingredient in marijuana – in the blood. Colorado, Washington and Montana have set an intoxication level of 5 parts per billion of THC.

“(Drugged driving) is something states have been looking at for a while because there have been issues with prescription drug abuse. This is something that needs more focus now that we have states allowing recreational marijuana,” said Erik Strickland, government relations manager for the Governors Highway Safety Association. “States want to find a way to keep their roads safe, and that involves trying to figure out what people are driving under the influence of and how it’s impacting them.”

Recent research into the effect of marijuana use on drivers is mixed, although many studies indicate drivers are less impaired by marijuana than by alcohol and tend to make fewer risky choices than drunken drivers. The National Institute on Drug Abuse maintains that marijuana significantly impairs judgment, motor coordination and reaction time, but other research shows stoned drivers overcompensate by driving more slowly and avoiding passing other cars.

The Maine Department of Public Safety warns on its website that pot use “produces a dreamy state of mind and creates the illusion that your senses are sharper than ever” even as the “‘spaced-out’ feeling” can reduce the ability to make quick decisions and judge time and distance.

How exactly to test drivers for impairment after they’ve used marijuana isn’t an easy issue for states to grapple with.

The standard being adopted in a growing number of states requires blood tests, which are not routine in OUI stops but are done in cases of serious traffic accidents when alcohol is suspected.

There is no simple roadside test for marijuana similar to the breath test used to determine blood alcohol content. Police officers currently can use a drug recognition exam on the roadside – which includes examining the eyes – to detect impairment from drugs. But some say they need better tools to stop drugged driving as the culture becomes more accepting of marijuana use.

According to a 2012 study published in the journal Psychopharmacology, 30 percent of people under the influence of THC failed a field sobriety test. The test’s ability to identify an impaired driver also seems to depend heavily on whether the person is accustomed to being stoned. Regular users of the drug may not be affected in the same way as first-time users.

Herbert Hill, a chemistry professor at Washington State University, is working to develop a device that can detect THC in someone’s breath. While it wouldn’t indicate if a driver was over that state’s legal limit of 5 nanograms of THC per milliliter of blood, it would tell police officers that some THC is present and a blood test could then be administered.

“I believe law enforcement does need some mechanism to test a person’s ability to drive while under the influence of marijuana,” said Chief Deputy William King of the York County Sheriff’s Office. “Alcohol is a legal substance that impairs a person’s reaction time – the same holds true for marijuana, but there is no test to determine the content of THC in a driver’s system.”

The focus on new laws to regulate marijuana use is the latest sign of momentum behind legalization efforts in Maine and nationwide. However, legalization advocates and supporters of the state’s medical marijuana program are raising concerns about the state setting a limit that is not based on clear science or that could unfairly target people who have recently used marijuana but aren’t impaired.

Urine tests show if a person has recently used marijuana and a person can test positive for weeks after using pot. Blood tests show the level of THC in a driver’s bloodstream, but not whether the person is actually impaired, according to advocates.

“We are all for reasonable guidelines regarding marijuana as prohibition ends. We need to have those in place,” said David Boyer, Maine director for the Marijuana Policy Project, which has been involved in legalization efforts in Maine and is pushing for a statewide vote in 2016. “It’s about impairment. You shouldn’t be impaired while driving, whether it’s from opiates, alcohol or marijuana. Our concern is that we don’t want people to get these (OUI) convictions for using marijuana eight hours before they drove, a day before they drove or even three days before they drove.”

Rep. Diane Russell, D-Portland, who plans to introduce her fourth marijuana legalization bill, said she has concerns about the marijuana OUI proposal.

“I don’t think the science is there yet,” she said. “The question shouldn’t be just about marijuana, it should be about impairment. The science hasn’t really caught up with that question of if that person is impaired. You can test positive for marijuana in your system for weeks, but you’re not impaired.”

The idea of testing drivers for the presence of marijuana in their systems also raises concerns for medical marijuana patients, said Hillary Lister, director of Medical Marijuana Caregivers of Maine. The group represents small-scale growers who sell medical marijuana to qualified patients.

“(The caregivers group) has been consistently opposed to that manner of determining intoxication since the amount of THC in your bloodstream doesn’t really relate to impairment. Medical marijuana patients will technically never be able to meet the blood level standard,” she said. “From speaking to law enforcement, they have tools like field sobriety tests.”

Police officers in Maine are trained to detect the presence of drugs other than alcohol in impaired drivers through the Drug Evaluation and Classification Program. The presence of abused drugs or controlled substances in the system can be used as evidence of impairment, according to state law.

Drivers under the influence of drugs typically have poor judgment behind the wheel or are not as aware of their surroundings as they should be, according to the Department of Public Safety’s website.

Referring to those operating under the influence of marijuana, the website says: “While it’s true that your attention becomes focused, you actually become preoccupied with unusual thoughts or visions, not the road. That ‘spaced out’ feeling alters your sense of time and space, making it difficult to make quick decisions, judge distances and speed, and causes slow, disconnected thoughts, poor memory and paranoia. Even hours after the effect is gone, this inability to deal with the unexpected lingers.”