It didn't take long to find one. A woman driving west on Main Street slowed to let a motorist pull out.

Fairfax City police Officer Rory Castillo punched the blue strobe light in his unmarked cruiser, flicked on his headlights and sent his siren wailing.

The suspect pulled over. Castillo bounded out of the car with a blue coupon book and prepared to write his first ticket of the day, good for a free carwash. Since June the city's police have been on the lookout for safe and courteous drivers and have been rewarding them with carwash coupons.

"I thought, 'What did I do? What did I do?' " said city resident Joyce Beach after Castillo had directed her into a nearby parking lot, torn a blue carwash voucher out of a coupon book and given it to her. "Thanks," she said, smiling. "Oh, boy."

Each day while on daily rounds, the city's four motorcycle officers look for drivers doing anything from yielding the right of way to cars or to pedestrians when not legally required to stopping to help a disabled motorist. The department plans to dole out 100 of the tickets and has given away more than 30 since the program began. The coupons, valued at $6, are good for a carwash at Embassy Autowash in Fairfax City and Manassas.

The program is similar to giveaways by other area police, although some departments question the practice of stopping drivers if they have done no wrong.

Castillo said the program is particularly valuable in Fairfax City, which often becomes a traffic island as major arteries dump commuter traffic onto the city's roads during rush hour and throughout the day.

"Most people are basically courteous, but it's easy to get short-tempered with all this traffic," Castillo said, as he sat at a traffic light during a courteous caper last Friday.

"Traffic's so heavy around here you just have to drive around and look," he said as the light changed. "Sometimes you go around a whole day and don't get any and sometimes you get two to three."

Nearly a half-hour passes before Castillo spots the second well-mannered motorist of the day, the driver of a silver Dodge Aries K who allowed a black Honda CRX to pull onto the roadway.

Castillo punches the appropriate buzzers and beams. The driver of the Dodge looks perplexed, pointing to himself and shrugging his shoulders as Castillo follows him down Main Street near Old Lee Highway. Two blocks later, city resident Charles Mankin turns into a parking lot and gets out of his car. Castillo quickly tells him why he has been stopped.

"I saw the police lights and I saw them smile and I said, 'That's the weirdest thing,' " said Mankin, referring to two passengers in the police car.

Mankin, a government agent, said he thought someone was playing a joke on him. Castillo tore off a ticket and gave it to Mankin, who was now smiling.

"And for being such a nice guy, is that all I get -- a carwash?" he asked.

After each stop, Castillo wastes no time explaining the program. He works quickly to reassure drivers that they haven't done anything wrong. The whole thing is over in less than a minute.

"I try to put them at ease right away because you can see the shock," he said. "You can pretty much see the wheels turning; it's pretty interesting to see the complete turnaround in reaction."

Fifteen minutes later, Castillo has spotted the driver of a silver Volkswagen Rabbit, stopped at a traffic light, who has left room for motorists to turn onto a side street.

"That's a good one because he had all that space to move up to," Castillo said, as he pulled the driver onto a nearby side street. Seconds later, he was shaking hands with Zakari Archer, of Triangle in Prince William County.

"On behalf of the Fairfax City Police Department, I would like to thank you for your courteous driving," Castillo said.

"No problem," Archer said. "I thought I was getting a ticket, but I guess I did pretty good."

Back on the road, Castillo figures on making one more stop before heading back to the station. He makes a loop around the city, but it seems the city's civilized have gone.

Castillo scratches his head.

"It's pretty much like fishing," he said, traces of a childhood spent on the gulf coast of Mississippi still in his speech. "Sometimes there's a lot of bites and sometimes there's none."