Managers of the project to extend Metrorail through Tysons Corner announced yesterday that they have revised their drawings and cut estimated construction costs by 25 percent, reviving prospects for building the financially troubled line.

Engineers said they have reduced the estimated cost of the 11-mile Metrorail extension from $2.4 billion to $1.8 billion by shortening a proposed tunnel through Tysons Corner, altering the "architecturally significant" design of the columns supporting the elevated portions of the track and revising the design of stations.

Neither the extent of the line nor the number and position of stations has changed, the engineers said.

"Our goal was to reduce the costs, not the service," said Sam Carnaggio, project director for the Virginia Department of Rail and Public Transportation.

The new price still exceeds by $300 million the project's $1.5 billion financing plan, and exactly who would foot the bill for the added expense has not been determined.

But Carnaggio and other key players seemed confident yesterday that the added costs were now manageable.

"I think this means that we are back on track," said Fairfax County Board Chairman Gerald E. Connolly. "The new number is not insurmountable."

The financing plan for the project has long assumed that the federal government would pay half and that the state and Fairfax County each would pay a quarter.

With a special taxing district on Tysons Corner landowners expected to generate a maximum of $400 million, Fairfax now would have to raise an additional $50 million toward construction.

The state is relying on money collected on the Dulles Toll Road to pay its portion.

"We have not identified any of the new funding sources," Carnaggio said. "We've just put the needs out there."

With the new price, the project still will be ranked "medium-low" for cost effectiveness according to federal standards, which is enough to win federal money by dint of recent congressional legislation allowing the project to be judged by less-stringent criteria.

Before yesterday's announcement, the long-anticipated plan to bring Metrorail through Tysons Corner had seemed on the brink of impossibility.

After estimates released in June showed that costs had risen 60 percent, to $2.4 billion, project leaders said that, given budget constraints and cost-effectiveness standards, it probably could not be built at that price.

Since then, teams of engineers have sought to make the cost-saving alterations to the design.

The most expensive single consideration in the project is the rail tunnel that goes through the hill on which Tysons Corner is built. Rail lines typically cannot slope steeply because the steel wheels can slip at even slight inclines.

By cutting the length of the tunnel in half, with the other portion of the rail line running on aerial tracks rising to as high as 45 feet through Tysons Corner, engineers said they cut the project cost by $200 million. The only planned underground station on the line, dubbed Tysons Central 7, is now essentially at grade.

The second-most significant savings were realized by changing the design of the columns that would carry the elevated portions of the rail line. About three miles of the rail line would run on elevated track, and engineers sought to make them visually appealing, as some neighbors and developers insisted. In places, those supports are placed roughly every 100 feet, engineers said.

The original piers had "an architectural identity," Carnaggio said. "The new ones are simpler, more commonly used."

An additional $20 million was saved by shifting a planned mezzanine at the station near Tysons Corner Center, the region's largest mall. That change probably would make station access more complicated for mall visitors.

Even with the price reduction, some critics of the project predicted that the savings will be short-lived.

"There will still be cost overruns when they will get into the construction," predicted Ken Reid, who has sought to organize opposition to the project. "Transportation projects generally run over the budget."

Opponents such as Reid have argued that even at the original price of $1.5 billion, the plan costs too much and does too little to alleviate Northern Virginia's traffic woes.

"Whether this is a $1 billion or a $2 billion project, it still does not make sense," Reid said.

Even after it's built, "it will cost taxpayers $20 million year after year in operating subsidies."

Many of the owners of properties abutting the rail line, although applauding the convenience of rail and helping to pay for the project through the special taxing district, said they were concerned by the implications of the elevated tracks running through Tysons Corner.

"We are all eagerly awaiting this information," said Michael Cooper, a senior vice president at Prentiss Properties, a commercial office owner.

"The aesthetics of a huge aboveground facility could be pretty dramatic. If you have something like that outside your window, it could have an impact on your property value," Cooper said.

Many Tysons Corner developers simply want to see the project built -- and soon, project supporters said.

"In a perfect world, we could design it to everyone's satisfaction," Connolly said. "But we don't live in that world."