What drivers need to know about increasing marijuana legalization before hitting the road

Marijuana legalization is gradually taking root throughout the U.S. as more states loosen restrictions on the formerly outlawed substance. Now, 23 states allow medical marijuana use, and four states—Alaska, Colorado, Oregon, and Washington—plus D.C. have legalized recreational marijuana use. Sixteen states are working on ballot measures for recreational marijuana use in 2016, and Vermont and Rhode Island may soon become the first to legalize marijuana by legislative action rather than popular vote. With a majority of states either allowing or considering some type of marijuana legalization, law enforcement, industry, and even insurance carriers have had to catch up quickly.

Earlier this year, we looked closely at how marijuana legalization has affected driving. The National Highway Traffic Safety Administration (NHTSA) has released a study comparing marijuana impairment to alcohol impairment. The results showed that crash risk increases exponentially with increasing BrAC (Breath Alcohol Concentration): a driver with a BrAC of 0.05 (which is still under the legal limit of .08) is 20 percent more likely to get into a crash than a sober driver, while a driver with a BrAC of 0.20 or higher (more than twice the legal limit) is 2,300 percent more likely to get into a crash than a sober driver. That means a person with a BrAC of 0.20 or higher is 23 times more likely to crash. Staggering. The same study found that drivers with THC in their systems were not any more likely to crash than a sober driver (when findings were adjusted for age, gender, ethnicity, and alcohol use). It’s important to note that no standardized way to measure a driver’s THC impairment yet exists, and states are still working out how to determine safe levels for driving.

As we enter 2016, we’ve rounded up all the latest updates and info you need to know about what’s legal and what isn’t when it comes to marijuana and driving, and how the legalization of a formerly tightly controlled substance might affect your auto insurance.

'Drivers with THC in their systems not any more likely to crash than sober drivers.'

Driver snoozing on steering wheel

Impaired Driving Laws

Though each state sets traffic laws, the rules about certain things, like driving under the influence of alcohol, are clear across the entire country: get caught driving with a blood-alcohol count above a certain pre-determined and easily measurable level (.08%), and you’ll be arrested and slapped with a DUI. But the rules for marijuana are much more obscure. The complication comes from the difficulty of assessing a particular driver’s level of impairment: no “THC breathalyzer” or other simple marijuana detection field test yet exists (though enterprising app creators have empowered drivers to understand their personal level of impairment). Drug recognition exams help police determine if a driver is impaired, but the exam is mostly visual (police examine the eyes, among other things) and therefore is imperfect. And so states have been left to determine what they think is best without a whole lot of scientific or standardized support.

Though field marijuana detection is imperfect, law enforcement isn’t shying away: in many states, drivers can be cited for DUIs if any THC is detected. In Arizona, for example, medical marijuana cardholders are subject to the same stringent state law as everyone else—namely, that any detectible THC in a driver’s blood stream is too much. Cardholders can refute their DUIs in court by attempting to prove the levels of the drug were too low to cause impairment at the time of arrest, but the stress, expense, and red tape of fighting a DUI are considerable. Another complicating factor: unlike alcohol, marijuana remains detectable for weeks after the last use.

Other states are attempting a more nuanced approach: take Maine, for example, which might be considering adding recreational marijuana use to the 2016 ballot. In anticipation, The Portland Press Herald reports that members of a study group are urging state legislatures to set a THC blood-level limit for drivers. Says the Herald, “The measure would make it a crime to drive a car while having a THC level of 5 nanograms or more per milliliter of blood.” In Maine, operating under the influence (OUI) already makes driving while under the influence of marijuana illegal, but no specific blood-level limit exists—yet.

Although specific laws vary by state, one thing is certain: even official medical marijuana cardholders must abide by impaired driving laws. Do not assume that just because your state has legalized medical marijuana use and you have the proper documentation that you can drive stoned. Just as alcohol use is legal but drunk driving isn’t, impaired driving—drugged driving—is illegal.

Cop reaching for driver's ID

Marijuana Impaired Driving Laws: What You Need to Know

The Governors Highway Safety Association (GHSA) reports the following marijuana laws:

  • 18 states have zero tolerance or non-zero per se laws for marijuana
  • 9 states have zero tolerance for THC (tetrahydrocannabinol, the psychoactive ingredient in marijuana) or a metabolite
  • 3 states have zero tolerance for THC but no restriction on metabolites
  • 5 states have specific per se limits for THC
  • 1 state (Colorado) has a reasonable inference law for THC

Specifics on each state can be found here.

The levels of THC are determined by a blood test. Complicating the laws is the fact that regular marijuana users build up a tolerance, so setting a hard blood-level limit is tricky. At 5 nanograms, someone who uses marijuana daily might show no impairment while an infrequent user might be danger on the road, making any specific number somewhat arbitrary.

If you use marijuana—legally, medically, or illegally (we do not endorse this)—it’s in your best interest to keep abreast of the laws in your state, and any surrounding states you might drive through. These laws are changing quickly all across the U.S., so keep current.

If you’re caught driving high, expect your insurance rates to skyrocket.

Marijuana and Auto Insurance

If you’re caught driving under the influence of marijuana and are convicted of a DUI (or OUI), expect your insurance rates to skyrocket, or your policy to be canceled outright. It’s no secret that the auto insurance industry operates on risk, and an impaired driver represents a significant risk—so significant that such a driver might have a very hard time finding insurance, and even if they do, they will pay an extraordinarily high premium. If you find yourself in this situation, help can be found here.

The bottom line for marijuana and driving? Know the laws in your state (and surrounding states), keep current on changing legislation, and never drive impaired.

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."

  • Toad Wallop

    Some people drive stoned everyday with zero problems. It’s not even close to drunk driving.