The "ripple effect," as Montgomery County Police Chief J. Thomas Manger called it, was supposed to make young drivers think twice before taking risks on the road. In the aftermath of three car crashes that killed five teenagers and injured four others during the weekend of Sept. 25, he had hoped that everyone would begin to wonder, What if that had been my child, my friend, my student? Or me?

"This is so devastating that it has affected even the most jaded among us," Manger told me a week ago. "Reporters are saying, 'This is unbelievable.' Cops who have been investigating these kinds of crashes for years are shaking their heads: 'This has got to stop.' As the ripple effect starts moving out, I hope we can translate this into something positive."

Nearly a week later, about 1 a.m. Saturday, however, two 21-year-olds were killed when their vehicle crashed into a sign pole in Silver Spring. Montgomery County police say the car was traveling at a high rate of speed and might have been involved in drag racing.

So what now?

A report released in March by the Insurance Institute for Highway Safety offers an overview of the problem that is hardly encouraging. Teenagers are disproportionately involved in motor vehicle crashes -- 5,933 such deaths were reported in 2002 -- making fatal injuries from car accidents "by far the leading public health problem for young people 13-19 years old," the report said.

Although the seriousness of the problem has been recognized for decades, the report said, "Most public policies have had little impact on the problem," including high school driver education programs.

Why?

"Thrill seeking tendencies associated with immaturity often overwhelm the effects of increased skills and knowledge," said the report, which added, "Deviant driving practices and crash involvement also are related to a syndrome of problem behavior including marijuana use, heavy alcohol use, smoking, and trouble with the law. The traits, values and peer associations of this high-risk group are such that changing their behavior through education is a difficult task."

But a new driver need not be "deviant" to be at risk. Any parent of an ordinary 16-year-old, for instance, ought to be extra careful before handing over the keys to the car.

"The combination of inexperience behind the wheel and immaturity produces a pattern of fatal crashes among 16-year-olds that includes the highest percentage of crashes involving speeding, the highest percentage of single-vehicle crashes, the highest percentage of crashes with driver error, and the highest vehicle occupancy," the report said.

Chief Manger said he wants parents to remember that new drivers lack the reflexes, eye-hand coordination and peripheral vision of experienced drivers. And though the law allows teenagers to drive until midnight, he said, that doesn't mean parents have to let them. Nor should parents take a cavalier attitude toward allowing their young drivers to let other teens ride with them.

"New drivers need to put their full attention on driving," Manger said. "They cannot be distracted by loud music or conversation. When you have two or three teens in the car, the driver is more likely to show off, take risks and do things he wouldn't do if he was alone."

The Insurance Institute notes that 61 percent of teenage passenger deaths in 2002 occurred in crashes in which another teenager was driving.

"I think every parent should take 30 seconds and think what it would be like not to see your teenager ever again," Manger said. "I can do it only for a short time, and it makes me sick to my stomach. I have two young children, and I think they would have to institutionalize me if something like that happened to them."

That's how the ripple effect was supposed to work -- deliver an aftershock to the conscience of a community. But in the aftermath of Saturday's fatal crash, the Montgomery police spokesman, Capt. John Fitzgerald, was still trying to make at least a drop in a bucket's worth of difference.

"Young people have got to drive like they've got something to lose, because they have everything to lose," he said at a news conference. "People just need to listen to this. They need to get it."

E-mail: milloyc@washpost.com