The drive to legalize the use of marijuana has spread across the country in recent years. At least 37 states have made it lawful to use the substance for medical or recreational purposes, or both.

But as people use marijuana more frequently and openly, the risks around driving while under the influence grow. And the prospect of more crashes linked to marijuana use also is on the rise.

“As recreational marijuana becomes more widely available, there are concerns about the potential dangers of driving under the influence,” says Pat Aussem, associate vice president of consumer clinical content development at Partnership to End Addiction, a New York nonprofit.

That reality can impact the rates you pay for car insurance.

Key Highlights
  • Thirty-seven states and the District of Columbia allow the use of marijuana for medical purposes.
  • Eighteen states and the District of Columbia allow the use of marijuana for recreational purposes.
  • States that legalized recreational marijuana saw increased collision claim frequency by 4% from 2012 to 019.
  • Following a DUI, car insurance rates jump by 80% on average and rates tend to jump from an average of $1,447 to $2,610.

How does marijuana affect drivers?

Marijuana and driving do not mix. According to the National Institute on Drug Abuse, driving under the influence of this substance impairs your:

  • Judgment
  • Motor coordination
  • Reaction time

Having THC – the psychoactive component in marijuana – in your body can reduce your ability to drive a car safely. In fact, marijuana is the illegal drug that shows up most often in the blood of drivers involved in crashes, according to the National Institute of Drug Abuse.

Those with THC in their blood are anywhere from three to seven times more likely to be responsible for a crash than those who drive unimpaired by any substance.

Tip iconInformation

There is evidence of an increase in the accident rate since marijuana legalization has happened in several states.

An examination by the Highway Loss Data Institute of insurance records found that legalizing retail marijuana sales in four states – Colorado, Nevada, Oregon and Washington – increased collision claim frequency by 4% compared with other Western states during the years 2012-2019.

Aussem says that the public needs to be aware of the potential risks of driving while under the influence of marijuana and that it is especially important to enlighten marijuana users about the amount of time they should wait before driving after smoking or vaping cannabis or consuming edibles.

How is marijuana regulated at the state and federal levels?

Laws related to marijuana use differ sharply between how the federal government views the substance and the way various states treat recreational and medicinal use.

The federal view is simple and clear: All marijuana use remains prohibited. However, that is often not the case at the state level. How many states have legalized marijuana? In truth, marijuana laws by state vary.

The overwhelming number of states – 37, plus the District of Columbia – allow the use of marijuana for medical purposes. Meanwhile, 18 states and the District of Columbia allow the use of marijuana for recreational purposes.

The Colorado Department of Transportation’s blog says that people who have consumed marijuana should do the following:

  • Wait at least six hours after smoking marijuana containing less than 35 mg THC before driving or biking. If you have smoked more than 35 mg, wait longer.
  • Wait at least eight hours after eating or drinking marijuana containing less than 18 mg THC before driving or biking. If you have consumed more than 18 mg or if you have consumed alcohol as well, wait even longer.

What are per se laws regarding marijuana?

A per se law prevents people from legally driving if they have specific amounts of a drug in their bodies.

For marijuana, per se laws define impairment as a certain amount of THC in a person’s blood. Aussem says this varies from state to state, but is usually between 2 ng/ml to 5 ng/ml.

“There is a tremendous debate as to whether these limits are accurate in reflecting impairment due to the different ways in which people metabolize the drug,” Aussem says.

Currently, 17 states have zero tolerance or non-zero per se laws for marijuana, according to the Governors Highway Safety Association.

The breakdown of these states is as follows:

  • Ten states have zero tolerance for THC (the psychoactive compound that makes people feel "high") or a metabolite (the molecule into which THC breaks down).
  • Three states have zero tolerance for THC but no restriction on metabolites.
  • Four states have specific per se limits for THC.

A single state – Colorado – has a permissible inference law for THC.

What are impairment laws regarding marijuana and how do they differ from BAC testing?

Unlike per se laws, impairment laws go beyond the substance you have in your system and focus on the quality of your driving and your behavior when you are stopped.

“Impairment laws typically rely on a drug recognition expert to assess an individual for impairment using a 12-step protocol,” Aussem says.

This includes items such as:

  • Blood-alcohol content
  • A statement from the arresting officer
  • A reading of the driver’s pulse
  • Examination of the driver’s pupils
  • Divided-attention tests
Tip iconInformation

Some states also use oral fluid testing “to confirm that substances are in a person’s system at the time of the arrest.”

Testing for the presence of THC in your blood can be challenging.

The Insurance Information Institute says there is no equivalent of a “breathalyzer” test for testing impairment from marijuana. While some have suggested that testing saliva may reveal a driver’s THC levels during stops, others say such results cannot accurately indicate a driver's level of impairment.

The AAA Foundation for Traffic Safety notes that the best way to test a person’s THC levels is to take a blood sample. However, that reality “has practical and constitutional implications for roadside testing.”

In addition, THC metabolizes quickly, so collection typically needs to happen within an hour of the person driving.

Aussem says better testing methods are needed to identify the level of impairment in people who use marijuana and drive.

In fact, she cautions that statistics about marijuana use and driver accidents can be misleading. Simply finding the presence of cannabis in a driver’s system does not mean the drug played a role in the crash.

“Someone could use cannabis on Friday night and get into an accident on Monday morning,” Aussem says. “THC would still be in the person’s system, but in this scenario, it would not be a reason for impairment.”

Marijuana laws per state: Which are per se and which are impairment?

Here is a breakdown of which states have per se laws and those that follow an impairment model:

Marijuana Laws Per State
StatesMarijuana Laws
AlabamaNo specific law for marijuana use
AlaskaNo specific law for marijuana use
ArizonaZero tolerance for THC and metabolites
ArkansasNo specific law for marijuana use
CaliforniaNo specific law for marijuana use
ColoradoPermissible inference for THC (5 ng)
ConnecticutNo specific law for marijuana use
DelawareZero tolerance for THC and metabolites
District of ColumbiaNo specific law for marijuana use
FloridaNo specific law for marijuana use
GeorgiaZero tolerance for THC and metabolites
HawaiiNo specific law for marijuana use
IdahoNo specific law for marijuana use
IllinoisTHC per se (5 ng)
IndianaZero tolerance for THC and metabolites
IowaZero tolerance for THC
KansasNo specific law for marijuana use
KentuckyNo specific law for marijuana use
LouisianaNo specific law for marijuana use
MaineNo specific law for marijuana use
MarylandNo specific law for marijuana use
MassachusettsNo specific law for marijuana use
MichiganZero tolerance for THC
MinnesotaNo specific law for marijuana use
MississippiDecriminalized
MissouriDecriminalized and legal for medical use
MontanaTHC per se (5 ng)
NebraskaNo specific law for marijuana use
NevadaTHC per se (2 ng) for felony violations
New HampshireNo specific law for marijuana use
New JerseyNo specific law for marijuana use
New MexicoNo specific law for marijuana use
New YorkNo specific law for marijuana use
North CarolinaNo specific law for marijuana use
North DakotaNo specific law for marijuana use
OhioTHC per se (2 ng)
OklahomaZero tolerance for THC and metabolites
OregonNo specific law for marijuana use
PennsylvaniaZero tolerance for THC and metabolites
Rhode IslandZero tolerance for THC and metabolites
South CarolinaNo specific law for marijuana use
South DakotaZero tolerance for THC and metabolites
TennesseeNo specific law for marijuana use
TexasNo specific law for marijuana use
UtahZero tolerance for THC and metabolites
VermontNo specific law for marijuana use
VirginiaNo specific law for marijuana use
WashingtonTHC per se (5 ng)
West VirginiaNo specific law for marijuana use
WisconsinZero tolerance for delta-9-THC
WyomingNo specific law for marijuana use

How a DUI can affect your auto insurance rates?

A DUI can have a major impact on how much you pay for auto insurance. In fact, following a DUI, car insurance rates jump by 80% on average and rates tend to jump from an average of $1,447 to $2,610.

If you are convicted of driving under the influence of marijuana, your auto insurance rates might increase, the Insurance Information Institute says. In addition, the III says that if legalization of marijuana leads to a significant increase in impairment that leads to more accidents, auto insurance rates could rise for everyone.

Learn more about DUI Insurance - Average Rates by State and Company

Sources:

  1. Cannabis (Marijuana) Research Report by NIDA

  2. State Medical Cannabis Laws by NCSL

  3. How Long Does Marijuana Stay in Your System Explained by Verywell Mind

  4. Drug-Impaired Driving Data - U.S. Map by GHSA

  5. Driving under the Influence Per Se Explained by New Mexico Criminal Law

  6. Marijuana and Impaired Driving Explained by III

  7. Major Issues Regarding the Impacts of Alcohol and Marijuana on Driving Explained by FTS