Metro: Marijuana impairment rising among drivers

During the last three years, Metro's forensics lab screened 4,500 blood samples for marijuana with the bulk of those being impaired drivers.
Metro said marijuana is dangerous because it slows down mental reactions and a driver's judgment of time and distance. Statewide records from 2002 to 2012 show 45 percent of drivers who were impaired by drugs had marijuana in their system.