Marijuana will become legal in California on January 1st. And while this has largely been greeted as good news, some people still worry about how legalization affects car accidents and fatalities. One of the big roadblocks to determining marijuana's impact on driving is the lack of a reliable breathalyzer test for the drug. But one company could be close to making that a reality.

Hound Labs based in Oakland says they are close to developing a reliable breathalyzer to determine whether people are impaired from marijuana. Currently, there are no reliable tests. Blood tests can't be used because marijuana can stay in a person's blood for days, even weeks, after use. And simply smelling cannabis on a person's body isn't enough because the scent can linger and could also just mean someone was in proximity to the drug. But Hound Labs says their test will make those options irrelevant.

The test created by Hound Labs determines if THC, the compound in marijuana that causes the psychoactive effects, is present in a person's breath. If it is, it means that person has used marijuana in the past few hours, and is likely impaired.

"It’s a huge technological and scientific challenge that we had to overcome," said Hound Labs CEO Mike Lynn said. "It took us a few years to overcome but we figured it out and we can measure just a few particles of THC, so it’d be like measuring a few drops of water in a hundred swimming pools put together."

The company says they are testing the final version of their breathalyzer and plan to launch it in 2018. It will cost $500 to $1000, and will be available for both law enforcement and individual marijuana users.

Also, while data does show that the number of car accidents has gone up in legal states post-legalization, there's been no link made between more people using marijuana and getting into accidents.

(h/t NBC Bay Area)