Lawmakers are considering a driving under the influence blood-content threshold for marijuana.
Under the proposal, drivers who test positive for 5 nanograms or more of THC, the psychoactive ingredient in marijuana, would be considered too impaired to drive.
One of the bill's sponsors is trying to assure medical marijuana users that they're not going to be stopped if they're driving appropriately.
While it's already illegal to drive while impaired by drugs, states have taken different approaches to the issue. Twelve states, including Arizona, Michigan, Illinois, Iowa, and Rhode Island, have a zero-tolerance policy for driving with any presence of an illegal substance, said Anne Teigen, policy specialist at the National Conference of State Legislatures. Minnesota has the same policy but exempts marijuana.
Nevada, which is among the 16 states that allow medical marijuana, and Ohio and have a 2 nanogram THC limit for driving. Pennsylvania has a 5 nanogram limit, but that's a state Health Department guideline, which can be introduced in driving violation cases, Teigen said.
The Associated Press contributed to this report.