Armed with new projections on future traffic congestion, the Fairfax County Board of Supervisors told Virginia highway officials this week to hurry up and build the new Dulles toll road.

"The board is a little fed up with the constant delays," Chairman John F. Herrity argued. "This road can be built -- the funding is available -- if we don't wait too long and let the costs increase."

The new road, which commuters have urged for several years as a way to unclog traffic in the county, would be parallel to the Dulles Airport Access Road. The access road is open only to airport traffic and, during morning and evening rush hours, to commuter carpools and buses.

The supervisors' request -- that construction on the road proceed "as rapidly but deliberately as possible" -- came after Virginia highway officials reported that traffic in the commuter corridor between Rte. 7 and Dulles Airport is expected to increase nearly 95 percent during the next 20 years. Failure to build the highway, the officials warned, could hamper growth in the area.

In a preliminary report that also outlined a timetable for construction, highway officials said the toll road will take 2 1/2 years to build and cost an estimated $33.5 million. A hearing on the plan is tentatively scheduled for June, with the start of construction estimated to be a year away.

"You have a (spending) ceiling imposed by the General Assembly," cautioned Supervisor Nancy K. Falck (R-Dranesville). "Where is the relationship of that to all these 'possible' and 'maybe' target dates?"

Although consultants on the project reported that their planning was right on schedule, Herrity and other supervisors said they wanted the highway department to understand fully the urgency of building the road.

In their report, highway officials noted that there would be no significant increase in air pollution caused by construction of the road. They warned, however, that steps would have to be taken to meet federal noise standards and to guard against possible harm to Wolf Trap Farm Park. The officials also alerted the board to possible flooding that could occur in some areas along the road, and said some neighborhoods would need special tree landscaping to protect their privacy.