Fairfax County police Capt. Tom Bernal was stuck in traffic the other day, his unmarked police car one of many going nowhere on a jammed Route 50. Suddenly, from about four cars in front of him, a car jerked out of line and sped off down the gravel shoulder. Bernal groaned and pulled out after him.

The commander of the police traffic division understood the young driver's frustration. "I've been sitting here 30 minutes," the driver whined. Bernal reminded him that pedestrians might be on the shoulder, or another motorist might be stopped with an emergency, and then a real disaster could have occurred. "He said he didn't think about it," Bernal recalled.

Without really trying, Bernal had reached precisely his unit's target driver: the aggressive, often unthinking, motorist. Last week, Fairfax County and Virginia State Police launched their latest three-week wave of RoadShark, a high-visibility, high-ticketing operation designed to reduce aggressive driving and diagnose places where it needs to be attacked more efficiently.

RoadShark began last fall amid some controversy, and after three rounds of increased enforcement, the verdict on its effectiveness is uncertain. Speeding violations seem to drop immediately after a RoadShark wave of enforcement, but then they return to previous levels.

Auto accidents have not significantly diminished yet, though police are getting a better idea of which areas to focus on. Police also have an increased sense that they are taking the offensive on managing the ever-expanding traffic blob, rather than waiting for the increasing population and vehicle volume to overwhelm them.

The program was announced last year as the area's most proactive attack on aggressive driving. In it, Fairfax police reassign as many as 30 officers a day during each campaign to interstates and other high-density driving areas. Many are in unmarked cars, and their locations are carefully chosen after consulting with crime analysts and community reports. "It's amazing the number of tickets they can write" from unmarked cars, Bernal said.

A burst of publicity accompanied the initial six-week RoadShark wave last fall. Police handed out T-shirts and bumper stickers and bought signs on buses to warn of the increased enforcement.

In the three weeks before the first RoadShark, about 2,300 speeding tickets were written. In the three weeks after it, fewer than 1,100 speeding tickets were issued.

But the number of crashes did not drop much, if at all. When a second, three-week wave was initiated in April, the number of accidents actually rose in the three weeks after RoadShark, and speeding tickets dropped off only slightly. The numbers aren't complete, but appear similar, for a third wave in June.

Some drivers complained that the program was simply a way for police to increase revenues by writing more tickets. And some driving experts have said that "road rage" is a myth created by the media to describe a phenomenon that has existed all along.

Bernal believes that road rage is no myth and that it is inevitable in a rapidly growing area like Fairfax County, with a road capacity that is practically choked already. "They get road-weary and frustrated," he said of area drivers, "which leads to doing things they normally wouldn't have done."

Both Bernal and the state police said their enforcement efforts weren't aimed at penny-ante speeders. "They're picking people up at ridiculous speeds," Bernal said, citing drivers going 90 mph and more as not unusual. Statistics show that more than 20 percent of the speeders stopped during RoadShark were driving more than 20 mph over the speed limit.

Lucy Caldwell, a state police spokeswoman, said state troopers weren't altering their methods during RoadShark but simply were providing Fairfax with more detailed information about where, and why, they're writing tickets.

"We do hope that we've put a dent in it," Caldwell said. "As a department, we've seen less aggressive driving incidents," and she noted that fewer anecdotes of gunfire or outrageous driving had been heard in Northern Virginia lately.

Officer Mike Uram, a Fairfax crime analyst who has compiled the RoadShark data, looked at the falling-and-rising rate of tickets and accidents and observed that modern drivers have short attention spans. Where at first they may have an awareness of RoadShark's increased presence--and surveys show that some drivers do know of it--the awareness soon fades and the willingness to speed or tailgate or wildly shift lanes returns.

So police plan to keep pounding away with RoadShark for at least another year, with not only speeding tickets and public service announcements but also warnings and letters. Yes, letters. Uram said Fairfax police had sent more than 1,200 letters so far to motorists whose license plates were called in by complaining fellow drivers, noting that they weren't being ticketed, but that they were being watched.

"I've been here 30 years," Uram said. "When we have programs in effect, in the short term, it helps." The goal of RoadShark, Bernal said, is to analyze the short-term gains and determine how to make them permanent.