09/14/2012 07:09 pm ET

Republican State Sen. Keith King Pushing For Marijuana DUI Standard For A Fourth Time

For the fourth time, Colorado lawmakers have voted to revisit a marijuana DUI standard to be introduced in January.

The bill, sponsored again by Mesa County Republican Sen. Keith King, proposes to limit drivers to 5 nanograms of THC per milliliter of blood--the same amount that was contested just last May when the bill failed by just one vote in the state Senate.

THC is the psychoactive ingredient in marijuana.

"People are dying on our highways and byways as a result of people driving under the influence of THC, just like with alcohol 20 years ago," King told the Associated Press.

Opponents last year however, brought up the point that THC levels are a problematic measurement.

Sen. Pat Steadman (D-Denver), arguing against last year's bill, brought up the fact that blood levels could remain above the 5 nanogram limit for days after a user has legally smoked pot, making them legally unable to drive though they may be sober.

If passed, Colorado would be the third state in the country to adopt a standard for THC blood content, and it would have the highest threshold. Nevada and Ohio both have a 2 nanogram THC limit for driving. Colorado is also just one of 16 states that allows medical marijuana use.