Six states that allow marijuana use legal tests to determine driving while impaired by the drug that have no scientific basis, according to a study by the nation’s largest automobile club that calls for scrapping those laws. The study commissioned by AAA’s safety foundation said it’s not possible to set a blood-test threshold for THC, the chemical in marijuana that makes people high, that can reliably determine impairment. As a result, drivers who are unsafe may be going free while others may be wrongly convicted, the foundation said.
