President Carter's bold, one-year-old federal pay program is still alive, but it is shrinking.

Within the past few months various U.S. installations have, for a variety of reasons, returned to freebie parking. And there is an outside chance that all U.S. worker-drivers may be freed from the shackles of paying for spots they once got free.

About 350,000 federal workers, including 50,000 here, went under pay parking last year. It grew out of an energy conservation speech the president made on television on April 5, 1979. In his message, Carter said the government would encourage its workers to bus, walk or car-pool to work by eliminating subsidized parking.

The program started with a groan in October 1979. It required feds to pay approximately half of the comparable commercial rate for an office parking spot. Full fees are supposed to be charged next fall. That could amount to $90 monthly downtown. If the program survives that long. The bureaucracy has been chipping at it since the day it started, and it has paid off for some.

Places like the CIA in Langley, Va., won early exemptions because of their remote location where commercial parking lots are nonexistent. Some agencies escaped pay parking on grounds that workers had no other way to get to the office. Some kept free parking because local lots charged $10 or less per month, with $10 being the government cutoff level.

Despite pay-parking rollbacks, which some feds compared favorably with the American victory at Yorktown, eight of 10 parking spaces controlled by the General Services Administration remain under pay parking.

Exceptions to the pay parking rule include -- naturally -- Capitol Hill where thousands of spots are reserved for legislators and some staffers.

Nearly half the U.S. parking spaces here are in Maryland. About 10,000 are in the District of Columbia and about 16,000 in Northern Virginia. Maryland is where most of the pay-parking protests have come from, mostly from U.S. types in Bethesda, which has its radical moments.

Many feds long long complained that pay parking guidelines were applied unfairly. Andrews Air Base did not have pay parking. Bolling AFB did. Bolling will return to free parking today, Dec. 1. Several defense installations have gone back to free parking. They include the Naval Academy (where workers threatned a June Week strike), Ft. Belvoir, the Naval Research Lab and Harry Diamond Lab, and the Defense Mapping Agency in Bethesda. Workers at Suitland Federal Center pay to park, but comparable commercial rates are right at the $10 breakpoint and if a new survery shows private lots charge less than that amount, Suitland again could become a free parking oasis -- if you can find a space.

Some General Service Administration custodial aides here who work odd hours recently won the right to return to free parking. But most people here in government continue to pay, even though rates are generally much lower than in commercial lots. Defense officials say that pay parking still is in effect at Ft. McNair, the Marine Corps barracks, Navy Yard, Naval Observatory (but not for Vice President Mondale's car), the Naval Security Station, Walter Reed, Naval Medical Center, Naval Military Personnel Center in Silver Spring, Arlington Hall, Naval Service Center, Ft. Myer and Henderson Hall.

The Pentagon, one of the world's biggest parking lots, still charges most peons (at the Pentagon that is anybody less than an admiral or general) to park. Relief from pay parking may be on the way. The American Federation of Government Employes has used to have pay parking overturned. Uncle Sam's lawyers went to U.S. District Court Judge Hoarold H. Greene asking him to dismiss the AFGE complaint. He refused and said that the union MIGHT have a case on grounds that pay parking was imposed administratively, rather than by executive order or law. Both the government and the unions are doing the necessary legal things to win. Whoever loses is sure to appeal. Until the legal fight is settled, pay parking will continue, but the number of people paying to park is shrinking every day.