The presence of THC in blood is not correlated with driving performance and is not a reliable indicator of psychomotor impairment, according to recommendations made by a state-appointed traffic safety task force.
A report issued by the Michigan Impaired Driving Safety Commission finds that peak THC blood levels are not associated with maximal behavioral impairment and further finds that the compound’s influence upon driving performance varies significantly among individual consumers. As a result, “The Commission recommends against the establishment of a threshold of delta-9-THC bodily content for determining driving impairment and instead recommends the use of roadside sobriety tests to determine whether a driver is impaired.”
Read the full article at NORML.