Nine out of 10 U.S. teensare not drinking and driving, according to a new CDC report released today.

“Teen drinking and driving has dropped by more than half in the past 15 to 20 years,” said Thomas R. Frieden, MD, MPH, director of the CDC, who spoke at a telebriefing.

While that news is good, “it’s really important we keep up the momentum,” he said.

Some teens have not yet gotten the message, he added.

In 2011, 1 in 10 students ages 16 and older reported driving after drinking during the past 30 days, according to the CDC report. And most of those had engaged in binge drinking, defined as having five or more alcoholicdrinks in a couple of hours.

That translates to about 950,000 high school students and about 2.4 million episodes of drinking and driving in the 30 days before they answered the survey, Frieden said.

“Teen drinking and driving remains a serious problem,” he said. “Road crashes are the leading cause of death in teens in this country and alcohol is a contributing factor in many crashes and deaths.”

The report is published in the CDC’s Morbidity & Mortality Weekly Report.

Teen Drinking & Driving: Behind the Numbers

For the CDC’s new Vital Signs report, researchers analyzed data from the 1991 to 2011 national Youth Risk Behavior surveys (in which teens answered questions). They also looked at fatal crash data.

Drivers ages 16 to 20 are 17 times more likely to die in a crash if they have a blood alcohol level of .08% than if they had not been drinking, the researchers found.

Frieden said the decline in teen drinking and driving is due mainly to three key changes:

• Minimum legal drinking age laws make it illegal to sell alcohol to anyone under 21 in all states.

• Zero tolerance laws, in effect in every state, make it illegal for those under 21 to drive after drinking any alcohol at all.

• Graduated driver licensing systems, in place in every state, help young drivers get more experience gradually under less risky conditions. While every state has these systems, the specific rules vary.

Society’s view of drinking and driving has changed for the better, too, Frieden said. “A generation ago, it wasn’t unusual to hear, ‘One for the road,'” he said of drinking.

“Now there is really a social understanding of how dangerous drinking and driving is,” he said. “There is now a sense that friends don’t let friends drink and drive.”

Teen Drinking and Driving: State by State

Of the 41 states with available data for teen drinking and driving in 2011, the rates varied from 4.6% of teens in Utah to 14.5% in North Dakota.

Besides North Dakota, these states also reported higher rates of teens drinking and driving. All had rates of 11.3% or higher:

• Alabama

• Iowa

• Louisiana

• Mississippi

• Montana

• New Mexico

• South Carolina

• South Dakota

• Texas

• Wisconsin

• Wyoming

Data were not available for California, Nevada, Oregon, Washington, Minnesota, Missouri, Pennsylvania, or Maine.

Besides Utah, the states reporting lower rates of teen drinking and driving, with 4.6% to 8.9% of teens reporting the behavior, included:

• Alaska

• Colorado

• Georgia

• Indiana

• Kentucky

• Massachusetts

• Michigan

• New York

• North Carolina

• Rhode Island

• Virginia

• West Virginia

Work Left to Do

To further reduce teen drinking and driving, parents can take a number of steps, Frieden said. “Parents are a key part of the equation here.”

They can lead as examples of safe drivers, and do so well before their child is of driving age.

Parents can also provide teens with a safe way to get home if they have been drinking and driving, he said.

Parents can also consider drawing up a parent-and-teen driving agreement, in which the teen agrees to such terms as obeying the speed limit and contacting the parents if he or she needs a ride home. The CDC has a model agreement that parents can use.