Hawaii lawmakers are asking how much marijuana a driver can safely consume before getting behind the wheel of a car.

It’s an issue they want to tackle now that Hawaii is setting up medical marijuana dispensaries, so Rep. Cindy Evans and 15 other lawmakers introduced a resolution asking the state Department of Health to study whether a person can safely drive while under the influence.

Marijuana is the illicit drug most frequently found in the blood of drivers who have been involved in accidents, including fatal ones, but the role marijuana plays in those accidents is often unclear because it can remain in the bloodstream for days and it’s often combined with alcohol, according to the National Institute on Drug Abuse. The National Highway Traffic Safety Administration says marijuana use impairs cognitive functions, lane tracking and other driving-related skills.

“I think that it’s really important that we do this now,” Evans said. “Hopefully this is the beginning of the discussion.”

For drunk driving, there’s a nationally recognized level of impairment, which is a blood alcohol concentration of 0.08 grams per millileter. But there’s no federal rule or widespread consensus on what’s an acceptable limit for driving under the influence of drugs.

Hawaii law bans people from driving under the influence of a drug that impairs their ability to drive, but there isn’t a set threshold for how much marijuana — medically prescribed or not — is acceptable in the blood stream.

Several states have passed laws specifying how much marijuana in the blood stream is acceptable while driving, but set different limits for how much THC — the main psychoactive ingredient of cannibus — in the blood would be considered driving under the influence of drugs. According to the National Conference of State Legislatures, Colorado, Montana and Washington set the limit at 5 nanograms per millileter of blood, while Nevada and Ohio went with the lower 2 nanograms. Other states provide an exemption for medical marijuana patients.

The state Department of Health opposed the resolution, saying the department doesn’t have the capacity to study the complicated question, especially because the resolution didn’t include funding. The department’s director, Virginia Pressler, said in written testimony that The National Institute on Drug Abuse has been studying this issue for many years and hasn’t been able to establish a recommended level for driving.

Despite the opposition, the House Committee on Transportation passed the resolution Monday, sending it to the Committee on Health to keep the discussion going, Committee Chairman Rep. Henry Aquino said.

“It’s here, so we just wanted to make sure that we have some sort of scientific, some sort of data-driven study to being done to address this,” Aquino said.