The American Automobile Association recommends states abandon such laws in favor of testing for actual impairment.
Legal blood limits for marijuana are not an accurate way to measure whether someone was driving while impaired, and can lead to unsafe drivers going free while others are wrongfully convicted, according to a new study.
The study released Tuesday by the AAA Foundation for Traffic Safety found that drivers can have a low level of THC, the active ingredient in marijuana, in their blood and be unsafe behind the wheel, while others with relatively high levels may not be a hazard.
Marijuana is not metabolized in the system in the same way as alcohol. So while a person with a blood-alcohol level of .08 or higher is considered too drunk to drive, it's not possible to say the same thing absent other evidence about a person testing at 5 nanograms per milliliter of blood of THC — the level used to find impairment by Colorado, Montana and Washington, the study found.