In a report recently released by the Oregon Liquor Control Commission, they found that intoxication due to alcohol is the greatest contributor to motor vehicle accidents. Additionally, there was no evidence of an "epidemic of THC-related collisions" since cannabis legalization. They also rejected the idea of per se limits for cannabis use. (Per se limits mean the act itself is inherently criminal, even with no demonstrable impairment.) This could eventually help to determine the difference in chronic, but not recent marijuana use when questioning driver impairment. For the full article from NORML, click the car!