Opponents of the Dulles Metrorail extension attempted to launch a tangled bouquet of multicolored balloons late last month in Tysons Corner to illustrate the rising cost of the project and revive a movement to stop it.

Talking over the sounds of sirens and trucks passing by on Route 7, a half-dozen community activists and current and former elected officials held a news conference on the oil-stained lot behind a Best Western hotel to argue -- once again -- that the rail project would cost too much, benefit too few people and ultimately do nothing to help congestion in the area.

The estimated price tag to extend Metrorail though Tysons Corner on its way toward Dulles International Airport has jumped by 60 percent, to $2.4 billion, and opponents hope that news will serve as additional ammunition in their difficult battle against the plan.

"The price increase is a blessing to the people of Fairfax," said state Sen. Ken Cuccinelli (R-Fairfax). He said the jump, from the previous estimate of $1.5 billion, will prove to the public that the rail extension is "a boondoggle."

"We can still stop this project," Cuccinelli said.

The group called for another environmental impact review, preferably by an independent commission, that would evaluate new design proposals and look at alternative uses for transportation funding. The opponents also said that decisions about spending for the project should be made by voters.

Cuccinelli promised to take a bill before the 2006 General Assembly that will require Fairfax County and the state to get approval from voters through a referendum before either sets aside funding for the operation of the rail system.

"All we've talked about is the cost of building," Cuccinelli said. "If God dropped it down tomorrow, everyone in Fairfax would have to pay higher taxes to subsidize the operations."

Many government and civic leaders in Northern Virginia consider the rail project a top priority. They say that without it, traffic will become worse in one of the nation's most heavily congested regions and economic growth will slow. In February, when the state agreed to a fee increase on the Dulles Toll Road to support the project, then-Secretary of Transportation Whittington W. Clement said: "The region clearly needs this project. Major roadways in the corridor are nearing gridlock. The problem won't go away, and we must address it."

According to a carefully negotiated financing plan for the rail's construction, the federal government would pay about half the project's cost and the other half would be split, with about a quarter coming from collections on the Dulles Toll Road and other state revenue, and about a quarter from commercial property owners along the rail route who have agreed to pay a special real estate tax.

The projects' engineers have proposed design alterations that could lessen the cost increase, including replacing a proposed tunnel beneath Tysons Corner with an above-ground and sometimes elevated rail. But opponents argued that many of the changes could make the project less desirable.

"Imagine pillars along this whole street," said Audrey Moore, a Democrat who served as chairman of the Fairfax County Board of Supervisors. She compared the proposal to an elevated rail line in New York City that was eventually torn down and that she said people called "a monstrosity." Moore and the others called attention to the balloons, mostly bouncing along the pavement, which were attached to 50-foot twine intended to show how high the elevated line would be.

"The whole point of the plan is to make Tysons more pedestrian-friendly," Bill Vincent, a longtime opponent of the rail project, said in a telephone interview. He said that to eliminate the tunnel and pedestrian bridges would drastically reduce the area's walkability.

Vincent, and the opponents at the news conference, advocated a rapid-transit bus system, which they said could run at a fraction of what a rail system would cost to build and operate. They also encouraged more high-occupancy vehicle lanes and a network of high-occupancy toll lanes, which would be free for carpoolers, buses and emergency vehicles.

John F. "Jack" Herrity, a Republican who was chairman of the Fairfax County Board of Supervisors, said it made sense to build rail in the 1960s and '70s, when most people worked downtown. Many people now, he noted, commute to and from jobs in the suburbs, causing a lot of congestion. He said those commuters would not be served by Metrorail, but would be forced to pay for it.

"Hundreds of thousands of people pay a toll so a few thousand people can ride a choo-choo train through Tysons Corner and benefit a handful of developers," Herrity said.

Chris Walker, founder of a group of taxpayers in the special tax district who oppose their portion of the financing plan, said that given the cost increase, he's confident that the project will fail. "Just look at the numbers," he said.

In a telephone interview, another longtime opponent of the rail extension was less sure. "We've talked to [our elected officials] for two years, till we're blue in the face," said Bruce Bennett, a retired salesman who lives outside Reston.

Bennett said he's worried about the increase in development density that the extension would bring. "We'll have to see what happens," he said.

The Metrorail extension would be partly paid for with revenue from the Dulles Toll Road, above.