WASHINGTON, D.C. (AP) - A National Highway Traffic Safety Administration survey conducted in late 2008 found that 20 percent of those 16 and older reported driving within two hours of drinking alcohol.

Based on the survey results, NHTSA estimates that 8 percent of all drivers, or 17.2 million people, have driven at least once over the course of a year, even though they thought they were drunk.

Additionally, 8 percent said they got a ride from a driver they thought was drunk. This was a particular problem for males between 21 and 24 years old. In this age group, 24 percent reported riding with a driver they thought had consumed too much alcohol.

On the positive side, the message about the dangers of drunken driving is widespread, with 81 percent of those surveyed seeing it as a serious public safety threat.

"We have got to do more, as a country, to close the gap between believing that drunk driving is a threat and actively doing something about it," NHTSA Administrator David Strickland said.

To warn motorists about the dangers of drunken driving, the government is spending about $13 million for an advertising campaign to publicize increased enforcement through Labor Day weekend.

NHSTA periodically conducts the National Survey of Drinking and Driving Attitudes and Behaviors.