Alcohol Use Down, Drug Use Up on U.S. Roads

The number of drivers under the influence of alcohol in the U.S. has plummeted from 36% in 1973 to just over 8% in 2013-2014, according to the National Highway Traffic Safety Administration.

But NHTSA's latest National Roadside Survey says drug use when driving is up. The study began tracking drug use including over-the-counter, prescription and illegal drugs in 2007. It reports the proportion of drivers testing positive for drugs on weekend nights since then increased 4%. The ratio of those drivers who had used marijuana grew by about 50%.

The study notes that alcohol use by drivers typically surges on weekend nights. Not so with drug use. NHTSA found virtually no difference in positive tests (22%) for drugs between weekdays and weekend nights.