A government survey found that the number of drunk-driving cases has fallen sharply over the last 30 years due to tougher laws and a shift in societal views on alcohol. However, a separate survey showed that for the first time, 16.3 percent of nighttime weekend drivers tested positive for drugs—mainly marijuana, cocaine, and methamphetamine. A roadside survey released by the National Highway Traffic Safety Administration found the 2.2 percent of drivers had blood-alcohol levels of 0.08 or higher in 2007. Government researchers last conducted the study in 1996, when 4.3 percent of drivers were legally drunk. In 1986, the number was 5.4 percent, and in 1973, it was 7.5 percent. Unfortunately, drugged driving is up. The most commonly detected drugs were marijuana (8.3 percent), cocaine (3.9 percent), and methamphetamine (1.3 percent). Researchers said that drugs can remain in a driver’s system for weeks, so it’s difficult to know whether those drivers were presently impaired. “This troubling data shows us, for the first time, the scope of drugged driving in America and reinforces the need to reduce drug abuse,” said Gil Kerlikowske, director of the Office of National Drug Control Policy. The survey examined weekend nighttime drivers, collecting breath samples to measure blood-alcohol concentration. For the first time, they also collected oral fluid and blood samples to determine a driver’s use of potentially impairing drugs. The study found a higher risk of encountering drunk drivers in the early morning hours—4.8 percent of drivers had an illegal blood-alcohol level from 1 a.m. to 3 a.m. on Saturday. The study also found that 1.2 percent of drivers were legally drunk from 10 p.m. to midnight on Friday, and that 0.2. percent of people were drunk during the day. The steady decline in drunk driving coincides with more stringent efforts by law enforcement and advocacy groups such as Mothers Against Drunk Driving to reduce drunk driving and use breath-monitoring ignition interlock devices for all offenders.