DENVER (CBS4) – Police and lawmakers face an important question now that smoking marijuana is legal in Colorado — how to keep streets safe knowing that more people are driving while high.

Police want to stress now that it’s legal in Colorado, it doesn’t mean it’s safe to get behind the wheel with THC in one’s system. Some lawmakers say limits need to be set so there are no questions and no excuses.

“(It’s) just like alcohol. If you have to experiment and you are experimenting with drugs, we have to know what that does to our body and when is too much,” Trooper Nate Reid with the Colorado State Patrol said.

Technically, it’s not known how much is too much. There’s no blood limit set like there is for drinking and driving. Troopers will simply arrest people if they feel someone’s impaired.

Former U.S. Attorney Troy Eid attended a marijuana discussion panel called “What Now?” The panel talked about a number of issues, including how high is too high to drive.

“The driving under the influence of drugs or DUID standard is not set in Amendment 64, so the legislature is going to have to set it,” Eid said.

One proposal sets the limit at five nanograms of THC per milliliter of blood. But there will be more questions to follow. The argument is that THC stays in the blood longer and doesn’t necessarily mean someone is impaired. Also, the only way to measure THC is a blood draw. Some could consider that invasive and refuse.

“There’s going to need to be a real discussion about how do you test people fairly, respect their rights, and make sure you’re accurate so you don’t jeopardize public safety,” Eid said.

Until then, police say designate a driver, take a cab, or just stay home.

The legislation setting a limit on how high is too high to drive will be introduced in January. Unlike drinking and driving it would let defendants argue in court that they weren’t impaired, but that’s a whole other issue.