Virginia Gov. Charles S. Robb yesterday urged that the federal government ease its restrictions on commuter use of the Dulles Access Highway and allow two-member car pools to have direct access to the restricted road during rush hours.

In a letter to the Federal Aviation Administration, Robb also urged that the FAA drop its current rule prohibiting commuters from "backtracking" to the Dulles International Airport terminal and driving on the federally owned highway with airport traffic.

The highway is presently restricted to airport traffic and to four-person car pools and buses during rush hours.

"By this action," Robb wrote, "we will be encouraging commuters to form car pools, we will reduce the flow of nonairport traffic to Dulles, and will reduce the congestion, noise and air pollution" on parallel roads.

Robb's letter is the latest development in a long debate between federal officials, who have sought to preserve the highway for airport use, and area officials eager to carve out a convenient commuter route for motorists in the populous Reston and eastern Loudoun County areas.

Presently an estimated 8,000 motorists use the roadway illegally each day, "backtracking" on the access road to the terminal and then driving east. The route is popular with these commuters even though it adds upward of 10 miles to their commute, because it avoids stop-and-go traffic in the Tysons Corner area.

The FAA this summer agreed to consider easing the highway's restrictions, and Rep. Frank R. Wolf (R-Va.) voiced the hope yesterday that the governor's recommendation would tip the balance.

"I'm optimistic," said Wolf, who has led local officials in calling for liberalization of the rules. "I'm very hopeful that we could get something positive on this within a month."

Federal officials declined, however, to predict the FAA's decision, which is due this fall in advance of the scheduled October completion of the road connecting the Dulles Access Highway to Interstate Rte. 66. "We will consider all comments," said Davis Hess, a spokesman for the FAA's Metropolitan Washington Airports agency. "We will be very interested in the governor's point of view."

Under the option backed by Robb yesterday, vehicles used in 2- and 3-member car pools would carry a sticker allowing them to enter or leave the highway at Reston Avenue or Trap Road during rush hour. Unless the cars have four riders the cars will not be allowed to continue toward Washington on I-66 during the morning rush hour, but would be required to exit on the Capital Beltway or on Rte. 123.

Robb argued yesterday that easing the rules on the access highway would reduce traffic congestion on the parallel Rtes. 7 and 50. It also would allow the Dulles road to accommodate more people without slowing the flow of airport traffic, he said.

Regardless of what the FAA decides, some relief for commuters should come in October 1984 when Virginia highway officials open a four-lane toll road parallel to the Dulles highway. At that time, the FAA again plans to restrict use of the Dulles highway to airport traffic.