A coalition of 14 civic associations yesterday attacked efforts by Montgomery County Executive Sidney Kramer to allow increased development in downtown Silver Spring.

The coalition said Kramer's plans would increase traffic by 60 percent and make Silver Spring's traffic the worst in the county.

A week after Kramer hosted a bring-your-own lunch to brief the press on his Silver Spring plan, the Silver Spring-Takoma Traffic Coalition provided sandwiches and brownies along with charts and maps detailing their objections to the executive's proposals.

"You have probably gotten the idea that a group of citizens are unhappy . . . . We want to move the emphasis from how upset we are to what we are upset about," said Pat Singer, president of the group which she said represents thousands of households in Silver Spring.

The County Council is about to begin a month of hearings and work sessions on a series of decisions that essentially will determine the scale of development in Silver Spring. A fierce debate has formed between those favoring a massive infusion of jobs and retail stores and those, such as members of the coalition, who say traffic will paralyze the area and its surrounding neighborhoods.

The coalition, by most accounts, has done an effective job of mobilizing the concerns of area neighorhoods now marked by hundreds of blue and white lawn signs that "Say NO to Gridlock in Silver Spring." Kramer, in turn, has ordered a public relations blitz of meetings and mailings to area residents.

Singer referred to a May report by the County Planning Board staff that an additional 10,000 jobs in Silver Spring would result in congestion at urban levels, or "the worst level of service for vehicular traffic, on the average, of any policy area in the county."

Kramer has recommended that 13,500 jobs be added to Silver Spring's job ceiling, a limit that stems from a policy that tries to ensure the adequacy of facilities such as roads and schools to match the allowable development.

Silver Spring will be able to handle the increased traffic, Kramer has said, because of plans for a transportation management system in which employers would be encouraged to have their workers use mass transit or to form car pools.

The Planning Board, while expressing some reservations about traffic, has endorsed the addition of 13,500 jobs.

Coalition members said yesterday they support the transportation system but said its goals -- increasing by 5 percent the number of current commuters using mass transit and getting 30 percent of all new Silver Spring workers to ride buses or join car pools -- are unrealistically ambitious.

A traffic engineer hired by the coalition found that the convenience of having one's own car may override some financial incentives planned by the county, according to coalition member Michael Z. Gravitz.

Coalition members stressed that they are not antidevelopment. They agree that the downtown needs sprucing up, but think the development proposed is excessive.