The chairman of the Metropolitan Washington Airports Authority said yesterday that car and van pools might be allowed on the Dulles Access Road during rush hour, but only until new lanes are completed on the parallel Dulles Toll Road.

In an informal meeting with Fairfax County officials, airports authority Board Chairman Linwood Holton said the board might consider opening the access road to car and van pools but "would insist on something tangible that tells them when we stop doing it."

Airport officials have long been reluctant to open the four-lane highway to anyone other than those going to and from Dulles International Airport. As traffic congestion worsens on the Dulles Toll Road, however, they have come under increasing pressure to allow some commuters to use the relatively uncrowded facility that runs alongside.

Last month, Rep. Frank R. Wolf (R-Va.) asked the airports authority to consider allowing car and van pools on the access road during rush hour until the toll road is widened or some form of mass transit is built to serve the airport. The proposal has been endorsed by the Fairfax and Loudoun County boards of supervisors.

"It's very bitter for people who live near Dulles and the area to the west to be denied use of the road that they feel their tax money went into," Vice Chairman Martha V. Pennino (D-Centreville) told Holton yesterday. "We're going to need all modes of transportation in that corridor -- not just bus, not just rail. It's got to be all of the above."

Two years ago, the Federal Aviation Administration, then the custodian of the access road, bowed to similar pressure and agreed to open the road to commuter buses during rush hour. Commuter vehicles of all types were allowed on the access road during construction of the toll road in 1982-83.

Holton said the airports authority will consider the latest proposal at its next meeting, Nov. 4. But he cautioned that the board's "first obligation" is to maintain easy access to Dulles, noting that airport use has increased from fewer than 4 million passengers in 1984 to more than 11 million in the 12-month period that ended in August.

The proposal is one of several being considered to improve access to the Dulles area, which has seen a dramatic increase in commercial and residential development in recent years.

The Virginia Department of Transportation plans to begin work next year on adding a lane in each direction to the Dulles Toll Road. Discussions are under way on the possibility of a rail extension to the airport, and a private firm is lobbying to build an extension of the toll road to Rte. 7 just east of Leesburg.

The sight of traffic whizzing by on the Dulles Access Road is an unending source of frustration to Fairfax and Loudoun county commuters sitting in traffic on the toll road. That road carried an average of 45,790 vehicles a day on its busiest section last year, compared with an average of 24,000 on the busiest section of the access road, officials said.

But airport officials caution that the access road is fast filling up. Average hourly traffic near the airport on a Friday afternoon now approaches 2,400 vehicles, beyond the rated capacity of 2,000 vehicles per hour, according to Henry Mahns, manager of the planning branch for the airports authority.