WASHINGTON - More than two-thirds of young drivers and passengers killed in nighttime car crashes are not wearing seat belts, a new report says.

Although seat-belt use is rising slightly nationwide, fatality figures published yesterday offered a somber contrast as law enforcement began 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, including New Jersey, at 91.4 percent. Pennsylvania was at 86.7 percent. Three states were below 70 percent: Arkansas, Massachusetts and New Hampshire.

But the news was hardly all encouraging.

Sixty-eight percent of drivers and passengers ages 16 to 20 who were killed in nighttime car crashes in 2006 were unbuckled, said the National Highway Traffic Safety Administration. During the 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.

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

NHTSA administrator Nicole Nason said teens frequently bring a "combination of inexperience and fearlessness" when they fail to buckle up. She said the agency was urging states to adopt licensing programs for new drivers that prevent them from driving with other teens in the car.