The federal government has given further approval to a planned Metrorail extension in northern Virginia that, if completed as envisioned, would extend the region's popular subway system to Dulles International Airport (web|news) .
The approval announced Wednesday is a critical step toward obtaining the needed $900 million in federal funding for the $5 billion plan to extend the Metrorail system through Tysons Corner and on to Dulles International Airport in Loudoun County (web|news) .
The project's future had been in doubt since January, when the Federal Transit Administration unexpectedly announced that it did not meet federal cost-efficiency standards. Virginia has been scrambling for months to bring the project into compliance.
Federal Transit Administrator James Simpson said Wednesday that the proposal has improved since January and that his agency will commit $159 million toward completing final design and engineering. But he said more work is needed before the feds will commit any construction funds.
Specifically, his agency wants to see the governments of Maryland, Virginia and the District of Columbia provide more funds to improve the existing Metrorail system, which already is running near capacity and showing signs of strain and disrepair.
Federal officials cited $489 million over the next six years in unfunded capital needs for Metrorail. 
"I can't tell you how important that is," Simpson said. "What good does it do to add 22 percent to a system that's not working?"
Still, Simpson acknowledged it would be rare for the FTA to deny construction funds to a project that has already received final design approval. if all goes well, the FTA could sign approve a full-funding agreement by the end of the year.
The 23-mile proposed extension would be built in two phases. The first would run from Falls Church through Tysons Corner to Reston, and it is this segment that is dependent on federal funding. The second phase, which would run from Reston to
Dulles and Loudoun County, would be built without federal funding under the current plan. Instead, it would be funded largely by tolls collected on the Dulles Toll Road.
Simpson said his agency examined whether toll-road revenue could support the second phase of the project, but under law could not consider that in its evaluation of the first phase.
"I don't know whether toll-road revenue ... can support Phase Two," Simpson said.
Proponents say the project would ease congestion in traffic-choked northern Virginia and allow for a transit-oriented redevelopment of Tysons Corner, a major business and technology hub. In addition, tourists and other travelers arriving at Dulles would have immediate access to the region's subway system.
Opponents say the project is too expensive and that other options, like bus rapid transit, should be considered.
Opponents also say the project's design cut too many corners to bring the price tag to an acceptable level, particularly by eschewing an underground tunnel through Tysons Corner for cheaper, elevated tracks that could prove more disruptive both during construction and after the project is completed.
Between now and January, when Simpson offered a gloomy assessment of the project's future, Simpson said several things had changed, including an improved partnership between the agency that runs Metrorail and the agency that runs Dulles airport, which will manage construction of the extension.
Simpson said the FTA also was able to verify $210 million in cuts that bring the first phase costs down to $2.6 billion, including design changes like smaller canopies at the rail stations and uses of concrete rather than more expensive tiles on the station platforms.
"It's not the same project" as in January, Simpson said. "It's really improved."
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