First there were flags, then signs -- and now fines. Starting Tuesday, motorists in La Plata who do not stop for pedestrians in crosswalks will have to pay up.

The police department gave drivers a heads-up last week about the $65 fine, issuing warnings to those who failed to yield on Charles Street. More than 50 were handed out during an hour-long operation involving a plainclothes detective playing the role of a pedestrian.

Motorists snagged in the experiment on La Plata's busy downtown drag were at various times frustrated, apologetic and, most of all, confused.

"I didn't know that. I'm glad you told me,'' said Vicki Shipp of Dentsville after she was pulled over and told about rule number one: As soon as a pedestrian's foot touches the crosswalk, a car in the same lane must stop.

"I thought they had to wait for traffic to stop and then dart across like I always do," Shipp said.

The aggressive enforcement of the state law comes a week after a 56-year-old Laurel woman was struck by a truck in the crosswalk in front of Civista Medical Center. The woman injured her hip, police said, when she tried to jump out of the way after realizing that the truck was not slowing down.

The driver, who was charged with failing to stop for a pedestrian in a crosswalk, could face a fine of up to $500 and two months in jail if convicted, said La Plata police Lt. Walter W. Wathen.

Mayor Eugene Ambrogio and members of the Town Council want downtown La Plata to become a hub for walking, shopping and dining, similar to Old Town Alexandria, Wathen said.

"We're trying to increase driver awareness and prevent further accidents," he said.

La Plata resident Betty Lou Richardson takes a deep breath before she crosses Charles Street twice a day from her car to her job at Civista's information desk.

"It's the thrill of my day," she said sarcastically. And then more seriously: "It's horrible. People don't like to stop."

La Plata has struggled with how to slow traffic on the downtown artery of Route 6. The town gave up on yellow warning signs in the middle of the roadways after the 30-inch-tall placards were mutilated and mowed down by cars.

Since then, Ambrogio has asked for additional stashes of orange flags at busy crosswalks for pedestrians to wave as they cross. The flags have had mixed results, too.

"It helps to make the pedestrian more visible, but in some cases," Wathen said, the cars "are still not stopping."

Before a change in state law this year, officers across Maryland were reluctant to ticket drivers because the law required alleged offenders to appear in court and carried the possibility of jail time.

"Now that it's a fine, we're more likely to hand out tickets," said Detective Sgt. William Brooks, who played the role of the pedestrian last week along Charles Street.

Deborah Rusaw, a house cleaner from Mechanicsville, was one of the drivers warned last week. She questioned the safety of giving pedestrians the right of way at all times.

"This city was not built for people walking," she said on the way to Nanjemoy. "If you're trying to watch the road, I can't be stopping."

Charles Street is so busy, Rusaw said, that stopping traffic for a pedestrian easily could cause an accident. She suggested a timed light for walkers instead of random crossings.

Even local government employees were guilty of forgetting. A chagrined Frances Sherman of Charles County's Public Facilities Department was one of the drivers flagged down.

"I completely understand. That was bad of me," she told the officer. "I think everyone should stop for pedestrians. If you don't do it every day, you forget."

Warning tickets are given to drivers who failed to stop for a pedestrian in a crosswalk on Charles Street. Officers will begin assessing fines Tuesday.Detective Sgt. William Brooks played the role of a pedestrian in the operation to issue warnings.