WASHINGTON — More than two-thirds of young drivers and passengers killed in nighttime car crashes aren't wearing seat belts — deadly proof of what can happen when young people don't heed parents' pleas and authorities' threats to "click it."

Though seat-belt use actually is rising slightly nationwide, fatality figures published Monday offered a somber contrast as law enforcement launched its annual pre-Memorial Day drive to persuade Americans to buckle up.

Total belt use rose to 82 percent last year — from 81 percent in 2006 — the government said. Twelve states had rates of 90 percent or better, led by Hawaii and Washington. Only three were below 70 percent: Arkansas, Massachusetts and New Hampshire.

But the news was hardly all encouraging.

Sixty-eight percent of drivers and passengers between the ages of 16 and 20 who were killed in car crashes at night in 2006 were unbuckled, said the National Highway Traffic Safety Administration. During daytime, 57 percent of the young motorists and passengers who were killed were not wearing seat belts.

That portion of the study focused on 2006 data and did not evaluate other years.

The problem isn't just with teens. The percentage of unbuckled drivers and passengers who died at night is well up in the 60s through the age of 44. It declines to 52 percent for people 55-64 and 41 percent for those older than that.

Safety officials say they are emphasizing seat belt use by young people between 16 and 20 during this year's "Click It or Ticket" publicity campaign through June 1. Police say they will be issuing tickets to motorists who fail to wear their seat belts, a message that will be supported by a $7.5 million advertising campaign.

Gabriela Sazon, a senior at Calvin Coolidge High School in Washington, is a believer from personal experience. But she also understands the problem among teenagers in general.

She and her mother avoided injuries two years ago when their car flipped on its side on a rain-slicked road. Both were wearing their seat belts.

Sazon said peer pressure can sometimes play a role in teens not buckling up. "They don't want to seem like a nerd around their friends," she said.

NHTSA administrator Nicole Nason said the agency is urging states to adopt licensing programs for new drivers that prevent them from driving with other teenagers in the car. She said carloads of teens traveling together can create distractions for the driver and increase the safety risks.

Anne McCartt, a researcher with the Virginia-based Insurance Institute for Highway Safety, noted that seat belt use at night tends to be much lower across all age groups.

Fatal crashes involving teenagers at night are more likely to involve risk factors such as alcohol, she said, so the failure to wear a seat belt "may be part of a more general atmosphere of risk-taking."