Twenty-three states and the District of Columbia have legalized medical marijuana use, four states have legalized recreational use, and many more have decriminalized marijuana possession. Marijuana regulation for drivers, however, is still in its early days. The National Highway Traffic Safety Administration (NHTSA) says that, “Drivers should never get behind the wheel impaired, and we know that marijuana impairs judgment, reaction times and awareness.” But without clear guidelines for detection or even what levels of marijuana are safe to drive with, states have been left scrambling for the best way to determine how much marijuana is too much to drive safely, and how to test for impairment in the field. As law enforcement and politicians figure out how to regulate whether drivers are too stoned to be on the road, drivers themselves are left to figure it out on their own.

An App that Empowers Marijuana Users

When marijuana was illegal in all cases across the nation, the answer was simpler: drive with any of the drug in your system, and risk arrest, fines, even jail. But now, it’s not so simple. If you legally smoke a joint and you’re beginning to feel the effects wear off, at what point can you get behind the wheel safely (even if the drug is still in your system)? Enter: My Canary, (as in, the canary in the coal mine), the five-dollar app that could offer marijuana users a reliable way to tell if they’re too stoned to drive.

The smartphone app (currently just for iPhones, with an Android app in development) is sanctioned by NORML, a marijuana advocacy group seeking to reform marijuana laws.

New app uses a reaction-time game to determine if a driver is too impaired to drive.

How it Works

As Business Insider details, the app involves four simple tests: “a memory challenge where you have to recall six numbers that briefly appear on screen, a reaction-time game where you have to quickly identify a particular icon from a series of images that pop up, a time-perception assessment where you have to count off 20 seconds in your head as accurately as possible and a balance test that uses your phone’s accelerometer to gauge your ability to stand motionless on one foot.”

A user’s results are then compared to personalized performance standards, based on their own past attempts at the app. Or, alternatively, a user can compare their results to performance standards built into the program. After the three-minute session, My Canary indicates whether a driver is too impaired to drive with classic traffic signals: A green light is all clear, a yellow light offers caution, and a red light warns of definite danger.

blurry street

Too High to Drive?

The most recent version of the NHTSA Roadside Survey of Alcohol and Drug Use by Drivers found that while alcohol use when driving has steadily declined (by more than three quarters since 1973), “nearly one in four drivers tested positive for at least one drug that could affect safety.”

Because marijuana is fat soluble (meaning it’s stored in body fat and not easily flushed out), a person using marijuana on a regular basis will have much higher levels of THC (Tetrahydrocannabinol: the main active ingredient in marijuana) in their system than someone who uses the drug less frequently, but because regular users often build up a tolerance, a regular user might be less impaired with more of the drug in their system than a more casual user, making determining who’s safe to drive all the more complicated. A similar sentiment was expressed by Marc Silverman, the developer behind My Canary. He told Business Insider that marijuana users should determine when it’s safe to drive based on their own performance, not on the level of chemicals in their body since the drug affects people differently depending on how often they use. This is also why blood tests aren’t a great choice: someone could ingest marijuana on a Monday and still have detectable levels on Wednesday, even if they no longer feel the effects of the drug.

Where marijuana legalization occurs, new driving laws should follow. Until then: There's My Canary.

My Canary: for Drivers, Not Law Enforcement

Silverman stresses that his app is not meant for law enforcement but is instead intended to help marijuana users figure out whether or not they should get behind the wheel. Silverman made it clear that data from the app isn’t uploaded anywhere, or stored on servers. Silverman told Business Insider, that he “wouldn’t feel comfortable allowing for law enforcement to use it” because each person needs to establish their own baseline within the app for accurate results.

We’d love to hear from folks who’ve tried My Canary—did it offer you helpful advice about your level of impairment?

About The Author

Julia is a writer living in New York City. She's written hundreds of articles about the auto industry, from demystifying car insurance to exploring the latest vehicle technologies."