Here's a classic good news-bad news study from the National Highway Traffic Safety Administration:
It appears that more than three decades of strong anti-drunken driving messages and stronger enforcement are having some impact. In a 2007 survey, NHTSA found that the percentage of drivers on weekend nights who have a blood-alcohol level higher than the prevailing national limit of .08 percent has fallen to 2.2 percent.
It's still pretty scary that one in 50 drivers on the road is drunk at those times, but that's an improvement from the downright terrifying 7.5 percent that prevailed in 1973, when the first such survey was taken.
During the daytime, the survey found that only 0.1 percent of the drivers on the road were legally drunk. But what your mama told you about being on the road when the bars let out is true: 4.8 percent of drivers were found to exceed .08 from 1 a.m. to 3 a.m. on weekends. That's nearly one in 20.
The news was less encouraging when it comes to drugs, screening for which was included for the first time in the 2007 survey. Based on oral fluid samples and blood samples, the survey found that 16.3 percent of the drivers on weekend nights tested positive for drugs. That doesn't mean they were actively high while driving, because some of the tests, such as those for marijuana, can yield positive findings weeks after use.
The most popular drugs among nighttime drivers in the voluntary, anonymous survey: marijuana, 8.6 percent; cocaine, 3.9 percent and methamphetamine, 1.3 percent.
Motorcyclists are also more than twice as likely to be drunk on the road late at night on the weekend. The survey found that 5.6 pecent of bikers had illegal blood-alcohol levels at those times, compared with 2.3 percent of those in passenger cars.
The survey didn't exactly debunk stereotypes: It found 0.3 percent of drivers of minivans were drunk on weekend nights, compared with 3.3 percent of drivers of pickup trucks.
Men also fared worse in the survey. Males were found to have illegal levels of alcohol in 2.6 percent of cases; females, 1.5 percent.