On Friday evenings, residents of Lincoln Park roam the streets in large groups, hoping to discourage the drug dealers who have long operated in the working-class Rockville neighborhood.

Now, after two years of a special community patrol by Montgomery County and city police, a Lincoln Park police substation has been permanently established.

The station, which opened last week, is in a house next door to the Lincoln Park community center and near a park that police describe as the center of drug activity in the neighborhood. It was purchased by the city of Rockville for $98,500 and replaces a temporary police office that had been set up in 1988, at the residents' request, in a town house at the Lincoln Terrace public housing project.

From the beginning, the Lincoln Park detail has been an unusual experiment in fighting the suburban drug problem and the county's most notorious open-air drug market.

It was not meant to be a tactical unit ready to storm suspected drug houses, but a highly visible team working to build rapport with the neighborhood.

Eight county police officers and two city officers are permanently assigned there.

"We wanted the new station to be central to everybody," said Rockville Police Chief T.N. Treschuk.

"It keeps the place clean for the kids to go out and play, for people walking by. There's a tremendous bond now between the neighborhood and the police."

The Lincoln Park experiment has been called a success by both community leaders and police, who last year recorded more than 700 arrests.

Lately, Treschuk said, there has been "a dramatic decrease in the number of arrests because of a dramatic decrease in the number of people selling drugs."