Cannabis Impaired Driving Laws

The growing threat of drugged driving is alarming. Policymakers are under tremendous pressure to do something about it, especially in states where marijuana has been legalized.

If a state decides to legalize marijuana, there should be consistent, strong and fair enforcement measures put into place to curb marijuana-impaired driving. Alcohol is legal and we enforce drunk driving laws as a way to keep the roads safe – we should do the same for marijuana.


Detecting Marijuana Impairment

Police can build cases against impaired drivers using a wide range of evidence, including the observations of experienced of trained officers, statements from suspects, results of field sobriety tests/evaluations, physical evidence in the car that indicates drug use, results of blood toxicology tests to corroborate drug use. An officer may make a determination that a driver is impaired based on observation of the driver’s behavior and performance on tests.


Training for Officers

Drug Evaluation & Classification (DEC) training and Advanced Roadside Impaired Driving Enforcement (ARIDE) training are currently the best tools available to law enforcement to combat drugged driving.

  • The Drug Evaluation and Classification program trains police officers as Drug Recognition Experts, or DREs. DREs assess a driver’s impairment using a standardized, research-validated 12-step protocol. If a DRE determines that impairment is present, he or she uses his or her observations to assess which category (or categories) of drugs may be causing the suspected impairment.
  • The Advanced Roadside Impaired Driving Enforcement (ARIDE) program was created to address the gap in training between typical law enforcement investigations, which use standardized field sobriety tests, and the evaluations performed by Drug Recognition Experts (DREs). Officers trained in ARIDE can identify drug impairment and know when to request a DRE evaluation.

All 50 states and Washington, D.C. have DEC programs, and police enforcement agencies across the country are working to increase ARIDE certification among traffic enforcement officers.


Per Se Laws

Every state has an alcohol per se law, which means that once a driver is shown to have a blood alcohol concentration (or BAC) of .08 percent, they are legally considered to be intoxicated. It means that having a blood alcohol concentration equal to or greater than the legal limit is by definition an offense, regardless of whether or not there is any other evidence of impairment.

Some states have established similar per se limits for marijuana, which would make it illegal, in itself, to drive with a certain amount of marijuana in their system. Per se limits have proven to be an effective method for enforcing alcohol impairment, but research does not show that drivers reliably become impaired at specific levels of marijuana in the blood. This is due primarily to fundamental differences between how alcohol and cannabis are process in the body and subsequently how they impair driving ability.

High drug levels may drop below legal thresholds before a test is administered to a suspected impaired driver. Marijuana also can affect people differently, making it difficult to develop consistent and fair guidelines. Using per se limits to prosecute motorists may result in some unsafe drivers going free and others being wrongly convicted for impaired driving.

As an alternative to enacting a marijuana per se law, AAA urges state laws should require A) a positive test for recent marijuana use and B) behavioral and physiological evidence of driver impairment, in order to convict a suspect of marijuana-impaired driving.

This system would rely heavily on law-enforcement programs to train officers in drug recognition.


Additional Resources

Read the study on Per Se Laws by the AAA Foundation for Traffic Safety:

Read the AAA Foundation for Traffic Safety report on drugged driving data collection barriers to learn about key issues states should address to better understand the drugged driving challenge: