The Federal Aviation Administration has proposed that Loudoun and Fairfax counties begin issuing windshield stickers this summer to low-occupancy car pools which the FAA would then allow to use the restricted Dulles Airport Access Highway.

The plan, according to FAA officials, would make it easier for them to weed out and ticket persons who, at rush hour, are driving the access road to the airport and then looping around--or backtracking--so they can use the lightly traveled highway as a commuter-road alternative to congested Rte. 7.

Supervisors in the two counties, however, immediately vowed to fight the proposed FAA crackdown on the backtrackers (who number at least 3,000, according to official estimates), charging that it was discriminatory and unfair to begin a crackdown now after allowing the practice to continue unchecked for years.

"It seems to me that there will be more police than citizens on the access road," said Loudoun Supervisor Travis L. Sample (D-Dulles), himself a backtracker who uses the access road every day to drive to his job at the Pentagon. "If backtracking is stopped completely, Rte. 7 is going to be a mess. I feel very strongly that this policy should be reconsidered and as soon as I can find out exactly what the FAA plans to do, I would be happy to lead the cause."

"I would vigorously oppose it," said Fairfax Board of Supervisors Chairman John F. Herrity. "Why should they crack down on something that's been going on for years now, just before the Dulles Toll Road opens?"

In an effort to discourage its use as a commuter route, the access road does not have entrance ramps open to commuter traffic heading east, as the highway was designed to provide quick access to the airport from downtown Washington. Backtracking has technically been illegal for years.

But FAA officials say they will open the access road to low-occupancy car pools (vehicles carrying two or three people) on an interim basis starting in June. The program would continue until the Dulles Toll Road is opened in late 1984.

Under the proposal, the FAA would allow two- and three-person car pools to "backtrack"--drive west to the airport terminal from Reston or eastern Loudoun and then return east--legally. But as part of the measure, the FAA said it would also come down hard on single-driver backtrackers.

The FAA first announced its intentions last fall, but the Loudoun supervisors didn't speak out until they saw the specifics of the proposal last week. According to information from the Loudoun Transportation Planning Office, the FAA has proposed putting in a license-plate surveillance system at the entrance and exit from the airport.

Cars with the low-occupancy stickers would be allowed to pass. Those without stickers would be timed by the surveillance system, and if they spent less than ten or 15 minutes at the airport, their drivers would be fined when they came back out.

Complicating the picture is the fact that, when the I-66 connector road is opened this fall and links the Dulles access road with I-66, cars bound for Dulles Airport will be allowed to use rush-hour restricted I-66 during rush hours even if there are fewer than four persons in the vehicles. That will make backtracking even more attractive and pose problems for the enforcement of I-66 restrictions, too.

FAA officials say that is why they have to get backtrackers off the access road.

"We would like to think we can pursue this in a neighborly fashion, but we have to make sure that all the traffic that gets to I-66 is legitimate airport traffic," said Frank Conlon, manager of the FAA's engineering division. "The surveillance system will help us build a history of regular backtrackers, and then we can send them a warning. It's our hope that, through an intensive public information program, we can make it crystal clear to people that use of the road is illegal."

Conlon said the FAA will ask for comments on the proposal as part of the FAA's rule-making procedure, but that he doubted that the FAA would reconsider the crackdown on single backtrackers. He said the FAA proposed allowing low-occupancy car pools as a way to accommodate backtrackers and that the FAA plans to approach Loudoun and Fairfax county officials soon about helping them issue the low-occupancy car pool stickers.

"We hope they will cooperate," Conlon said.

Loudoun Democratic Supervisor Betty Tatum, whose Guilford District includes part of Sterling Park, said that she has already begun to hear from angry constituents, however, and that as soon as the word gets around she expects to hear from many more.

"They are anywhere from upset to furious," said Tatum. "I think the FAA is just causing a big headache for itself."

Some Loudoun supervisors said it is difficult for Loudoun County residents to form car pools because people in the county live far apart. Sample said the plan would hit Loudouners especially hard because they do not have the alternative of Metrobus service that is available in Reston and Herndon. And some members said they thought it would hurt businesses located at the airport because people would be confused about restrictions on the access road.

Fairfax Supervisor Martha V. Pennino, whose Centreville District includes Reston, said she would support a move to ask the FAA to reconsider cracking down on the Dulles backtrackers.

"I really don't blame them for backtracking on the road because it was paid for with taxpayers' money," said Pennino.