Two-member car pools could be using the Dulles Airport Access Road during rush hours as early as August, the Federal Aviation Administration indicated last week.

The FAA, which agreed in March to ease its restrictions on commuter use of the federally owned highway, will make those plans formal today with an announcement in the Federal Register.

After a 45-day comment period--until July 22--and a brief review period, the new rules could go into effect as early as August, according to Henry Mahns, manager of the FAA's regional planning branch.

The car pool agreement, reached by the FAA and Rep. Frank R. Wolf (R-Va.), will cut in half the four-person car pool rules that have been in effect on the access road for almost three years and make the illicit "backtracking" practice unnecessary for many Reston commuters. Backtracking allows Washington-bound motorists to gain access to the restricted airport highway by driving west to the Dulles terminal and then heading east on the road.

The two-person car pools will not be allowed during the morning rush hours to continue into Washington on I-66 once the Dulles road is linked to the interstate in September or October. The two-rider cars will have to exit the access road at the Beltway, Mahns said. Traffic to and from the airport will be allowed on I-66 at all hours once the so-called Dulles connector is opened.

When the parallel Dulles Toll Road is opened in late 1984 or early 1985 the access road will again be restricted to airport traffic.

Still to be resolved with Loudoun and Fairfax counties is a decal or sticker system to identify car pool vehicles. FAA police and Virginia state police will use the decals to distinguish the commuters from airport traffic, which will be allowed on I-66.

FAA police will begin their long-announced "crackdown" on single-occupant backtracking commuters when the new two-person car pool rules become effective, Mahns said. About 3,000 commuters a day illegally use the access road by driving to the airport terminal in the morning and then turning back toward Washington with airport travelers.

Four-person car pools have been allowed to use the Wolf Trap Farm Park and Reston Avenue entrances and exits during weekday rush hours.