Golden shovels in hand, a cross-section of Virginia politicians--Gov. Charles S. Robb, Sen. John W. Warner, Rep. Frank R. Wolf and Fairfax County Board of Supervisors Chairman John F. Herrity among them--gathered yesterday morning for the first official excavation for the long-awaited Dulles Toll Road.

"We in Fairfax County may not be brilliant, but we're persistent," said Herrity, as speakers harked back to the 14-year campaign to construct the 12-mile, four-lane highway. "First I-66, then the Dulles connector . . . this is the last link in Fairfax County's historic mission to connect Dulles airport with the Potomac."

The $57 million toll road, funded by a state sale of revenue bonds in December, is being touted as a potential Yellow Brick Road to greater economic growth in the already rapidly growing section of western Fairfax.

"The first thing the chief executives of Tandem and Sperry said to me was, 'We moved here because you promised to build the Dulles parallel lanes,' " said Herrity.

"We're making good on that promise to them, and to all those bringing jobs and tax base to this corridor," he added.

Warner said the road, in relieving traffic congestion along Rtes. 7 and 123, would provide "greater flexibility and opportunities to area residents" as well as attracting new development.

Warner also told a crowd of local bureaucrats and businessmen that he had received a commitment from outgoing U.S. Secretary of Transportation Drew Lewis "to release $56 million to Metro to purchase 60 [subway] cars to complete the Orange Line to Vienna."

Once toll revenues have repaid the state's debt--estimated to take 20 years--the tolls will be lifted, officials said. Highway officials have estimated that by 1985, the toll highway will be used by 29,000 cars a day, and as many as 49,000 by the year 2000.

Tolls will be staggered according to distance, ranging from 25 to 85 cents for the entire 12 miles. Interchanges are planned at Rtes. 123, 7 and 128, the Capital Beltway, Hunter Mill Road, Wiehle Avenue, Reston Avenue, Centreville Road and the proposed Springfield Bypass.