It’s been a long and winding road, but the Colorado General Assembly has finally passed a driving-stoned standard for motorists.

The measure — which is expected to be signed into law by Gov. John Hickenlooper — establishes a marijuana blood standard by which it is illegal to operate a vehicle.

“Smoke and walk. Smoke and take the bus. Smoke and grab a cab. Smoke and call a friend. Smoke and ride a horse. Smoke and take the light rail,” said Sen. Steve King, R-Grand Junction, a bill sponsor, during a recent Senate debate. “Just don’t smoke and drive. Your life and every other citizen’s life on the highway is at risk.

The bill passed the Senate May 7 on a 23-12 vote, after it had previously cleared the House by an even wider margin.

The bill limits drivers to five nanograms per milliliter of blood for active THC, marijuana’s psychoactive ingredient.

But that limit would be known as a “permissible inference” standard by which a person is considered to be under the influence of the drug. However, a defendant can rebut in court whether he or she was actually impaired.

That’s different from a strict “per se” standard, such as the 0.08 percent blood-alcohol concentration used to prosecute drunken drivers.

Opposition to the bill knew no party lines. Sen. Pat Steadman, D-Denver, voted no on the legislation, arguing that there are laws already on the books that make it illegal for people to drive while impaired.

“What’s the problem we’re trying to solve here?” Steadman said.

And Sen. Kevin Lundberg, R-Berthoud, cautioned that a driving-stoned limit could lead to “too many false positives,” due to residual amounts of the drug being in the bloodstream of a person who regularly smokes the drug, but may not have been stoned behind the wheel at the time of arrest.

“We should not be convicting people who are not guilty of driving while impaired,” Lundberg said.

Sen. Andy Kerr, D-Lakewood, had voted no on setting stoned-driving limits in the past, but voted yes on this “reasonable” piece of legislation, this time around.

“With all of the lines we have to draw here at the Capitol … I think we have to draw a line at some point (on driving stoned),” Kerr said.

Members of the Capitol press corps dubbed the effort the “zombie bill” because it continued to surface at the legislature, in spite of having suffered multiple deaths.

The bill had failed four times in previous years — and it even suffered two separate deaths before it finally passed this session.

The original bill passed the House, but failed in a Senate committee. A driving-stoned standard was then tacked on in the form of an amendment to an Amendment 64 regulation bill, before it was stripped from that legislation by a separate committee.

The bill’s House sponsors were House Minority Leader Mark Waller, R-Colorado Springs, and Rep. Rhonda Fields, D-Aurora.