40 percent of drivers killed in 2013 tested positive for drugs, study says

The number of people driving under the influence of drugs appears to be on the rise, according to a new study.

The study, released by the Governors Highway Safety Association, found that 40 percent of drivers who were killed in 2013 tested positive for drugs. That covers everything from meth to blood pressure medication.

Marijuana was detected in about a third of the cases.