A Rockville civic association's opposition to the city's planned extension of a roadway through its neighborhood suffered a major setback recently when a federal judge denied a motion to halt construction.

The College Gardens Civic Association filed suit against Rockville last year, claiming the city could not extend Gude Drive without first preparing an environmental impact statement.

The county and both the federal and state highway administrations were named codefendants in the suit, which claimed the Gude Drive extension was part of a larger highway project to be financed by the county, state and federal governments, and therefore regulations required an impact statement.

But on Aug. 28, U.S. District Judge Joseph H. Young ruled that although Gude Drive may become part of that highway system, it is a separate city project and no impact statement is needed.

Rockville wants to extend Gude Drive from Md. Rte. 355 to Research Boulevard, and $6 million in city and county funds has been appropriated for the work.

The extension will become part of the long-planned Rockville circumferential highway, a proposed four-lane road that will pass within 100 feet of some College Gardens homes.

Another highway segment, known as the First Street extension, is already under construction. It is supported by both federal and city funds.

The association has been fighting the project since its inception a year ago. The group, citing potential noise, air pollution and safety problems, approached the council with an alternative plan in July 1980. City officials rejected the proposal, saying it would cost more and take more time.

Rockville officials believe the east-west extension will reduce downtown traffic, according to a city spokesman.

Melvin Halpern, spokesman for the civic association, said the group last week voted to appeal the judge's decision.

"This suit is our last resort," he said. "We have given up trying to reach a compromise with the city."

Barring a successful appeal, construction of the extension is expected to start in the spring, according to a city spokesman.