The National Park Service announced yesterday that it plans to permanently close a central section of Rock Creek Park to automobiles within two years and impose traffic restrictions in sections of the park this spring in a move to make the 93-year-old park safer for bicyclists, joggers and pedestrians.

The decision, which does not become final until a two-month public comment period ends April 30, follows more than three years of studies, public hearings and trial closings of park roads north of the National Zoo.

While several traffic changes would go into effect May 1, there would be no major impact on the 20,000 commuters who drive through the park until 1985, when the 1.5-mile section of Beach Drive between Joyce and Broad Branch roads would be permanently closed.

The restrictions planned for the federal government's oldest urban park are similar to those imposed over the past decade on auto traffic in New York's Central Park.

Top D.C. transportation officials and a coalition of 21 environmental and recreational groups supported curbs on Rock Creek traffic at Park Service public hearings two years ago and a Metropolitan Washington Council of Governments study last year concluded that such traffic restrictions, including even a ban on cars on all of Beach Drive, would have little impact on local traffic.

But American Automobile Association spokesman Thomas Crosby said yesterday it was a "foolish, ill-advised decision" to close any section of Rock Creek Park to cars, even in 1985 when the Metro subway is open to upper Montgomery County and construction is completed on 16th Street.

The Park Service plan would delay the Broad Branch-to-Joyce Road closing until those projects are completed in an attempt to lessen the impact on commuters.

Park Service regional director Manus (Jack) Fish yesterday said the proposed changes would not severely inconvenience motorists, and would make the scenic, historic park safer and available to more people. He added that the Park Service will consider changes in the plan.

More than 200 accidents a year occur on the narrow upper-park roads, where pedestrians and bikers now share the roadway with cars. U.S. Park Police surveys show that 98 percent of motorists exceed the park's speed limit of 25 miles an hour.

The Park Service will hold an all-day open house to discuss the changes and hear comments on them March 23, and will review written comments received by April 30.

The Park Service also plans to close one lane of the section of Beach Drive between Joyce and Broad Branch roads year round during rush-hour traffic, beginning May 1, to permit bicyclists and joggers in the lightly used lane.

The service also intends to close this section and two others to cars on weekends and holidays while daylight saving time is in effect. The other sections of Beach Drive to be closed on this basis are between Sherrill Drive and Wise Road, and from West Beach Drive to the Maryland line.

Thomas M. Downs, D.C. director of public works and transportation, said last night that he favors the changes proposed for Beach Drive this spring "which will affect very, very few people" and give the Park Service a chance to experiment with greater bicycle use of park roads.