The National Park Service's controversial plans to restrict automobile traffic in Rock Creek Park and improve safety conditions for bicyclists and joggers got a mixed reception at three recent public hearings.

Most of the 300 area residents who attended the hearings were bicyclists, joggers and speakers for a coalition of more than a dozen environmental and recreational groups. They generally supported closing parts of Beach Drive above the National Zoo to rush-hour automobile traffic.

The coalition proposal, which the Park Service has said it will consider in addition to its own less restrictive proposals, would permit local traffic and auto access to 27 of the park's 30 picnic areas. But only pedestrians, bicyclists and horses would be allowed in what is considered the park's most scenic sections.

Changes being studied by the Park Service are designed to provide a safe route for bicyclists and joggers along upper sections of Beach Drive, where there is no bicycle trail and where bikes and pedestrians now share the narrow, winding road with cars. Numerous accidents have occur red in this section of the park, according to U.S. Park Police, although there have been no fatalities in recent years.

The long-range Park Service goal has been to "reduce excessive commuter traffic" in the park in an effort to curtail noise, air pollution and traffic hazards.

The nine Park Service proposals include closing various sections of Beach Drive to through traffic during rush-hour, giving one of its two lanes to bicyclists and building up to six miles of separate bike trail. However, a separate trail is unlikely, Park Service officials admit, because it would require extensive construction along the stream and would cost as much as $1 million.

Another public hearing will be held this fall, when the Park Service tentatively chooses one of the alternatives or a combination of them. The final decision, by Regional Superintendent Manus (Jack) Fish, is expected to be made next spring.

Most motorists at the hearings and many nearby residents objected to curtailing commuter traffic in the park.

Lawrence Coltin, a commuter who lives two blocks from the park and drives through it every day to work, said, "The number-one outdoor recreation activity is scenic driving." He opposed closing the park to commuter traffic, but said he felt sure the Park Service could come up with a compromise solution "that accommodates bikers, joggers, horses and cars."

Darrell W. Neily of Beltsville, Md., called Rock Creek "the safest, most pleasant route to the city. I don't want to see a permanent closure of any kind," he said, adding that he would support any practical measure to improve bicycling in the park.

Brock Evans, a Sierra Club official, told Saturday's hearing, "We're fighting for the place we love . . . so automobiles (should) only have part of the park." Rock Creek is the second oldest federal park and one of the largest urban parks in the United States. The club is part of the coalition.

Robert P. Donaldson, a George Washington University professor of biology and nutrition who lives in Takoma Park, Md., and commutes by bike on park roads, said, "A man or a woman on a bike is the most efficient thing moving on the face of the earth," adding that it is unsafe to allow both bikers and cars on the winding, narrow lanes of Rock Creek Park.

One auto commuter, Earl L. Ziebell of Chevy Chase, Md., urged that bikes be given one of lane of Beach Drive, with reversible rush-hour traffic in the other. "You don't need expensive barriers. It could be done with signs. Do it now," he urged the Park Service.

One speaker proposed construction of bumps along park roads, similar to those on 46th Street NW, to slow auto traffic. Park Police surveys show 98 percent of motorists in Rock Creek Park violate the park's 25-mile-an-hour speed limit.

Although the hearings have ended, comments on the proposals can be made in writing to the Park Service until May 17.