'When Is It Going to Stop?'

Police said they had not determined where the young women had been, or where they were going, as they headed west on the inner loop of the Beltway toward the Springfield interchange. Tyler said investigators would be looking into that, as well as the source of the alcohol.

The car was in the middle lane of five on the Beltway at 10:40 p.m., according to Steve Titunik of the Virginia Department of Transportation. The exit for southbound Interstate 95 involves the two left lanes, separated from three through lanes by a wedge of striped pavement. A construction project a short distance farther west on the Beltway did not contribute to the crash, Titunik said.

The car passed the entrance to the exit, Titunik and Tyler said, and then cut left across the striped pavement back toward the exit ramp and into the path of a 2007 Freightliner tractor-trailer carrying a full load of frozen foods. In the right lane of the ramp, the Freightliner smashed into the car, drove it into a retaining wall and flipped it over, Tyler said.

Three of the occupants were ejected. The car was demolished, and investigators could not tell whether the convertible top had been up or down, or whether seat belts had been worn.

The Freightliner was driven by Glenwood B. Spears, 42, of Sanford, N.C. He was not hurt. No charges were filed, and state police said he was not at fault.

Teresa Spears said her husband arrived home in North Carolina yesterday afternoon beset with grief. He had been in Army Special Operations before retiring and taking a job as a truck driver more than a decade ago.

"When you're talking about four young lives on the brink of so much potential, there's nothing to compare," she said.

"He's not one of those gung-ho, macho men. He's a loving and caring and giving person," Spears said. "We're just remorseful. We're just praying for the families, you know. Our kids are just not long out of school themselves. I couldn't imagine the heartache those families must be feeling. . . . I just couldn't imagine the void."

Her husband was not up to speaking about it, she said. "I know this is going to affect him for a long time. But it really isn't about him right now. It is, but it isn't. It is about the four families. My husband . . . Those children," she said, beginning to weep.

It was not clear whether anyone in the Cabriolet planned to attend West Potomac's all-night graduation celebration Thursday at the ESPN Zone in Northwest Washington. A bus from West Potomac was scheduled to leave the school at 11 p.m., 20 minutes after the crash, for an alcohol-free bash that school officials said was only for graduates, and only for those who arrived on the bus. Attendees could not leave the party and were returned to West Potomac at 5 a.m.

With so much experience dealing with teen crashes, schools in the Washington area have revamped driver's education programs, initiated after-graduation parties and used such old but proven methods as displaying wrecked cars on campuses.

Some school districts offer seminars for parents that distill the lessons that make up their children's courses. In Prince William County, school officials offer a mandatory 90-minute seminar to parents whose kids are taking the schools' driver's education program.

Last night, about 150 people gathered in front of the West Potomac campus for a candlelit vigil. Bunches of pink and white roses, cards and snapshots of crash victims with friends and classmates were placed next to a rock.

"One day ago, everyone was really happy," said Jeff Dietze, the student activities director. The school, he said, formed a bond with its graduates. For those who died, he added, "We can't say we ended it on a good note."

Staff writers Amy Orndorff, Joe Holley, Debbi Wilgoren, Michael Laris, Ian Shapira, Tara Bahrampour and researcher Karl Evanzz contributed to this report.