Responsible stoners agree on one thing: lighting up before you get behind the wheel is a bad idea. There hasn't yet been sufficient research to determine for sure whether legalization in the U.S. has resulted in a higher incidence of car crashes. However, it's well-known that being high slows reaction time, makes drivers more likely to weave between lanes, and effects motor skills - all things you, and your fellow motorists, want to avoid.

Although 18 states have placed limits on marijuana intoxication while driving, it's been a real challenge for law enforcement officers to recognize when someone is, in fact, driving under the influence.

As NPR has reported, police in Washington can seek a warrant to test drivers suspected of cannabis impairment for THC. But it can take weeks for results to come back from the toxicology lab. Police have to rely on fairly inexact telltale signs like red eyes or a smell of marijuana in the vehicle. As a result, there's been a push from scientists, law enforcement, and researchers to develop a breathalyzer that detects cannabis impairment.

Hard to pinpoint when THC entered the system

The challenge in developing such a device has to do with the way THC is stored in the body. According to Oakland-based Hound Labs, whose cannabis breathalyzer, The Hound, is patent pending, "although measuring THC in blood, urine, or saliva is relatively easy, this type of testing doesn't distinguish recent use from chronic use [...] Frequent marijuana users often will have elevated levels of THC in their systems. Even if they haven't smoked marijuana in several hours and are therefore unlikely to still be impaired."

Although Hound Labs says the science is "proprietary" and they currently "cannot go into too much detail about how it works," once it's optimized in a handheld device, it will both make cannabis impairment easier to detect, and ensure that unimpaired individuals who may have THC in their system because, say, they smoked a joint the previous day, don't get arrested.

It's an ongoing race to keep the roads safe, as Civilized reported earlier. Vancouver's Cannabix Technologies, as well as a group of scientists from the Washington State University in partnership with Chemring, have also built prototype cannabis breathalyzers. So, if you're one of those hotshots who swears you're a better driver when you're high, take heed: your days of flying down the highway could be numbered.

h/t Time, NPR