Researchers at the University of North Carolina are evaluating whether graduated driver's licensing programs adopted across the United States are effective at saving teen motorists' lives.

In the past decade, wrecks killed more than 23,000 teenage drivers and 14,000 of their passengers. Graduated license programs hope to give teens more time to learn the rules of the road and increase their driving skills.

"The idea is to let them get some experience under their belts before we expose them to the full risks of driving," said Scott V. Masten, a doctoral researcher with the California Department of Motor Vehicles.

Some states allow a 16-year-old to be fully licensed. California allows full driver's licenses by age 17. North Carolina lifts all restrictions when the driver is age 18.

Dzenta Delic has been driving for two years, graduating from a permit to a full license.

"I started with my dad, and he taught me the rules. My mom let me drive her car, and so that was a real big step," Delic said. "When they felt I was ready, they let me take my test."

Researchers with the California DMV examined data from 22 years of fatal crashes with teenage drivers nationwide.

They found that graduated license programs saved lives among 16-year-old drivers. "They're also associated with an increase in fatalities among 18-year-old drivers," Masten said.

"We find that the benefits aren't as large as we had hoped they would be when we implemented these programs nationwide," he said of the study, which appears in the Journal of the American Medical Association.

Researchers said further studies are needed to figure out why older teens do not appear to benefit as much from current graduated driver's license programs.

Until then, they said, practice behind the wheel and paying attention on the road helps make better and safer drivers.