The Colorado Senate has passed a measure that would make it easier to convict someone of driving while under the influence of marijuana. The measure will now move to the House, according to The Denver Post.

A similar measured passed the Colorado House last year, but was defeated in the Senate. The bill would make it a crime to drive with more than 5 nanograms per milliliter of THC—the psychoactive chemical in marijuana—in a person’s blood.

While it is already a crime to drive under the influence of marijuana in Colorado, there has been no standard for when a person is legally considered “high.”

“All we’re saying is don’t smoke pot and then get behind the wheel,” State Senator Steve King, who sponsored the bill, recently told a local newspaper. He noted that although traffic fatalities in Colorado have decreased over the last four years, traffic fatalities related to THC have increased by 50 percent over the same period.

State Senator Morgan Carroll, who chairs the Senate Judiciary Committee, said the bill could hurt legitimate medical marijuana patients. She said research is not conclusive about a specific THC level at which everyone is impaired. “If you’re going to put science in the statute, it needs to be pretty good science,” she told The Denver Post in January.