New Research Sheds Light On Inaccuracy Of Legal Limits For Cannabis Intoxication

AAA’s research arm, the AAA Foundation for Traffic Safety strives to “prevent crashes and save lives through research and education about traffic safety.” This organization released this week a comprehensive report which analyzes the limits set by many states meant to indicate cannabis intoxication. Fascinatingly this report found that the nanogram per milliliter (ng/mL) limits currently set by states do not accurately determine the level of intoxication of an individual. This mindset of a quantitative approach to qualifying intoxication is a carryover from our understanding of measuring and controlling alcohol intoxication. Most states have settled on a limit of 0.08 BAC for alcohol, and 5 ng/mL for cannabis. To be clear, no patient should get behind the wheel and drive if they are under the influence of any drug and impaired or intoxicated.

This report found that it is not scientifically sound to use the same logic with cannabis as is applied to alcohol. While the BAC limit has been scientifically shown to be a consistent and reliable determination of alcohol intoxication, the AAA study showed that the same is not true for cannabis. The study showed that first time or new users with a small amount of cannabis in their blood can be highly intoxicated, while conversely regular users with a high amount of cannabis in their blood can be not intoxicated at all. Paradoxically, unlike with alcohol, the research showed that measured amounts of cannabis in the bloodstream do not correlate linearly to a measured level of intoxication. This is why the report concluded that “there is no science showing that drivers reliably become impaired at a specific level of marijuana in the blood.”


Marshall Doney, AAA’s President and CEO, feels that “in the case of marijuana, this approach is flawed and not supported by scientific research. It’s simply not possible today to determine whether a driver is impaired based solely on the amount of the drug in their body.” AAA goes on to advise lawmakers to create a system which does not hinge on arbitrary limits alone, but instead “use a two-component system that requires (1) a positive test for recent marijuana use, and most importantly, (2) behavioral and physiological evidence of driver impairment.” Without this approach Illinois may end up chasing its own tail in court, as was the situation in Colorado. For some more insight into what driving on cannabis looks like, check out this documentary by CNN showcasing an experiment on how cannabis can affect driving. Following the experiment in the video you can watch Sanja Gupta as he actually takes a ride in a car driven by a medicated patient.

Some news outlets have been trumpeting scary headlines like Marijuana-related fatal car accidents surge in Washington state after legalization or Report: Fatal marijuana-related crashes up where drug is legal, both implying the number of fatal car accidents caused by cannabis has been trending upward. CBS news straight up misrepresented the findings from AAA and left out the explanations of the details in the study. Like that cannabis was in many cases not the only drug present in the driver’s system in the fatal crash, and the number of fatal drivers with only cannabis in their system is surprisingly low. One of the most important details include that while the presence of cannabis in drivers of fatal car accidents may be trending upward, this has no correlation to their level of intoxication at the time of the accident.  As NORML’s Paul Armentano puts in the the AAA news release, “We should not conflate the detection of certain substance with the notion that the driver was necessarily impaired with certain substances.” He referenced a NHTSA study released in 2015 which found that driving impaired by cannabis is in no way statistically similar to driving impaired by alcohol.

An excerpt from the Behavioral Safety Research (February 2015) Drug and Alcohol Crash Risk By Richard P. Compton and Amy Berning:
This study of crash risk found a statistically significant increase in unadjusted crash risk for drivers who tested positive for use of illegal drugs (1.21 times), and THC specifically (1.25 times). However, analyses incorporating adjustments for age, gender, ethnicity, and alcohol concentration level did not show a significant increase in levels of crash risk associated with the presence of drugs. This finding indicates that these other variables (age, gender, ethnicity and alcohol use) were highly correlated with drug use and account for much of the increased risk associated with the use of illegal drugs and with THC. This study found a statistically significant association between driver alcohol level and crash risk both before and after adjustment for demographic factors. These findings were generally consistent with similar analyses conducted in prior crash risk studies. Findings from this study indicate that crash risk grows exponentially with increasing BrAC. The study shows that at low levels of alcohol (e.g., 0.03 BrAC) the risk of crashing is increased by 20 percent, at moderate alcohol levels (0.05 BrAC) risk increases to double that of sober drivers, and at a higher level (0.10 BrAC) the risk increases to five and a half times. At a BrAC of 0.15, the risk is 12 times, and by BrACs of 0.20+ the risk is over 23 times higher.


Illinois residents need to be responsible consumers and understand the laws in this state which regulate cannabis drugged driving. Currently the law states “It is unlawful person to operate a motor vehicle while there is any amount of a drug in the person’s breath, blood or urine.” To restate that in more simple terms, that means anything above zero will result in a DUI for cannabis in Illinois. This should strike fear into the hearts of regular users who understand the facts, and know that they can fail a urine screen drug test for anywhere from 0-120 days, and a blood test for anywhere from 0-3 days after they have last medicated with cannabis. The reality of the situation today is that the only real way to steer clear of a cannabis DUI in the state of Illinois is to either not use cannabis at all, or not drive at all. The medical cannabis legislation which was passed in Illinois which allows legal cannabis access does not offer any exemptions for medical cannabis patients from DUI convictions.

This is important for Illinois residents to understand this topic clearly because the current decriminalization bill working through the Illinois State Legislature will modify the limit from 0ng/mL and set a new limit of 5ng/mL for intoxication of cannabis while driving. The best way for Illinois legislators to keep Illinois roads safe is to take note of the new AAA research and not use a blood ng/mL measurement as the sole deciding factor of intoxication in DUI cases. Please look up your Illinois State Congressional representation and contact and inform them of the AAA & NHTSA research, help them understand the reality of cannabis intoxication and how it does not correlate directly to a ng/mL level, and that our state needs to be smart about how we regulate cannabis drugged driving. Let’s set a new shining example in Illinois for the rest of the country to follow!

Do you think our state is taking the right approach when it comes to setting legal limits for cannabis intoxication? Let us know what you think in the comments below or on social media!

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