It may not have borne the significance of Promontory Point, Utah, where they drove in a gold spike to celebrate the first rail link with the West Coast in 1869. But there was a sense of hoopla and exuberance yesterday when local dignitaries hammered a gold (plated) spike into a wooden slab placed temporarily atop a new bridge over the Dulles Airport Access Road.

"This is really a happy and historic moment for Reston," declared Francis C. Steinbauer, the Reston Land Corp. executive who oversaw the bridge's two-year construction. His remarks were heard by a noonday crowd that included about 75 local elementary pupils sitting on the freshly-paved bridge that carries Wiehle Avenue over the airport road.

The steel and concrete bridge is the final link in Reston's road network. It is the second span to join the northern and southern halves of the 12-square-mile Reston community. Farther west, the Reston Avenue Bridge opened two years ago.

Part of yesterday's happy mood may have been a reflection of the fact that the new $775,000 span seems to be a bargain with something in it for everyone concerned.

The Reston Land Corp., the latest developer of the new town, is happy because it got the bridge merely by prepaying its county property taxes for 3 1/2 years. The span substantially enhances the value of the company's property at the bridge's southern end, where intensive development is under way.

The Virginia Department of Highways and Transportation is presumably happy with the new bridge because, although it built it, no one asked the state to pay for it.

State highway funds are customarily used for road construction, but in this instance the state considered the facility to be a low priority item, Fairfax County transportation planner Sam Chamberlain said yesterday.

The project had much public backing and so the Fairfax County Board of Supervisors agreed to pay for the bridge's construction with the Reston Land Corp. prepaid taxes.

The $775,000 in funds supploed by the Reston Land Corp. was essentially "a gift" from the county to the state, Chamberlain said yesterday.

The new bridge will also save the county the cost of building a second fire station in the Reston area.

But the bridge is also probably the last such cooperative venture of the county government and private industry. Transportation planner Chamberlain said that the supervisors have adopted a policy of no longer allowing prepayment of real estate taxes to subsidize road construction.