Since 1993, the profile of a drugged driver has changed substantially. A study shows that more drivers are now testing positive for prescription drugs, cannabis, and multiple drugs, and they are more likely to be older than 50. The study finds that the percentage of drugged drivers with three or more drugs in their system nearly doubled from 1993 to 2010, increasing from 11.5 percent to 21.5 percent. “In 1993, about 1 in 8 drivers were using multiple drugs concurrently. By 2010, it was closer to 1 in 5. That’s a large increase in drug use,” one author said.