Americans are increasingly driving while high, according to a pair of new studies released by the federal National Highway Traffic Safety Administration (NHTSA).
Drunk driving has decreased by one-third since 2007 and three-quarters since 1973, according to the NHTSA's 2013-2014 Roadside Survey of Alcohol and Drug Use by Drivers, which collected oral fluid or blood samples from 11,100 drivers at 60 locations across the country.
Nearly one-quarter of drivers tested positive for at least one drug that could affect safety, according to the survey, which has been conducted five times during the last 40 years.
Drivers with evidence of drugs in their system on weekend nights climbed from 16.3 percent in 2007 to 20 percent in 2014, and those with marijuana in their system grew by nearly 50 percent during that same period.
A second study, the Crash Risk Study, found that marijuana use by drivers is associated with a greater risk of crashes, but the study notes that marijuana users are more likely to be in population segments (i.e. young males) that crash at higher rates regardless of drug use.
Read the Roadside Survey of Alcohol and Drug Use by Drivers HERE.
Read the Crash Risk Study HERE.