The National Highway Transportation Safety Administration’s most recent National Roadside Survey shows declines in drunk driving but an increase in use of marijuana and prescription drugs on the nation’s roadways.

The survey found the number of drivers with alcohol in their system has declined by nearly one-third since 2007 and by more than three-quarters since 1973.

Yet, the same study found a large increase in the number of drivers using marijuana or other illegal drugs, with one in four drivers testing positive for at least one drug that could affect safety.

Read entire article: http://www.nhtsa.gov/About+NHTSA/Press+Releases/2015/nhtsa-releases-2-impaired-driving-studies-02-2015