The Oregon Liquor Control Commission advised state lawmakers not to amend the state’s traffic safety laws or institute per se thresholds for cannabinoids. The recommendations were part of a new report issued by , which had been tasked with reviewing the state’s driving laws following the passage of legislation in 2015.

Per se means that the presence of a certain amount of a given drug in the bloodstream, in and of itself, constitutes proof of impairment. That is simply not true for cannabis. The Commission reviewed the data and flatly rejected the adoption of per se traffic safety laws as a standard for cannabis impairment.

No major impact on driving attributable to cannabis

Authors concluded that intoxication due to alcohol, not marijuana, remains by far the greatest contributor to motor vehicle accidents and found “no evidence” of an “epidemic of THC-related collisions” post marijuana legalization.

They further reported, “[S]tudies that have been conducted tend to show an elevated risk of crashes while under the influence of THC, but generally a lower overall risk as compared to alcohol impairment.”

Per se levels may work for alcohol but not for cannabinoids

Specifically, authors acknowledged that drivers with a blood alcohol level of .08 possess approximately a 400 percent increase in motor crash risk compared to sober drivers. By contrast, recent crash culpability studies of marijuana-positive drivers report an elevated risk of accident of 30 percent or lower.

Authors also rejected the idea of imposing per se limits that criminalize the act of operating a motor vehicle if the driver possesses detectable amounts of specific drugs or drug metabolites above a set threshold. Under these laws, drivers are guilty per se of violating the traffic safety laws even absent evidence of demonstrable impairment.

Authors acknowledged that evidence quantifying THC/blood levels with psychomotor impairment is not available at this time. Rather than imposing such non-scientific standards, they recommended the creation of standardized field detection tolls “that are able to detect recent use and impairment, separate from levels of THC that may be due to chronic but non-recent marijuana use.”

Recent reports by both the American Automobile Association and the US National Highway Traffic Safety Administration also reject the use of per se thresholds as predictors of cannabis-induced driver impairment.