WOOD-TV Grand Rapids reports that a state commission determined that Michigan should not set a limit on how much THC drivers can have in their system before they’re deemed impaired:

The commission, whose members were appointed by former Gov. Rick Snyder, includes a representative from the Michigan State Police, a registered medical marijuana patient, a forensic toxicologist, a licensed physician and two university professors with expertise in the areas of traffic safety and cannabis pharmacology and toxicology.

“Based on the total body of knowledge presently available, the Commission finds there is no scientifically supported threshold of THC bodily content that would be indicative of impaired driving,” the report reads in part. “There is a poor correlation between driving impairment and the blood (plasma) levels of THC at the time of blood collection.”

According to the commission, THC levels in blood drop rapidly, but impairment happens more slowly and peaks after blood levels have already dropped. Additionally, level of impairment varies based on prior usage.

“The implications of tolerance to cannabis are that lower blood THC levels in infrequent users may result in impairment that would only be experienced at higher THC levels by regular cannabis users,” the report’s authors wrote. “Therefore, because there is a poor correlation between THC bodily content and driving impairment, the Commission recommends against the establishment of a threshold of THC bodily content for determining driving impairment and instead recommends the use of a roadside sobriety test(s) to determine whether a driver is impaired.”