The U.S. Dept. of Transportation has formally committed $900 million to help construct the first phase of the Silver Line, a 23-mile extension of Washington, D.C.’s Metrorail system to Dulles International Airport in Virginia. The funding, which has been closely scrutinized due to concerns about the $5.2-billion project’s schedule and cost, allows the Metropolitan Washington Airports Authority (MWAA) to move ahead with the initial $3.1-billion, 11.6-mile above-ground segment from the existing East Falls Church Station to Wiehle Road in Reston, Va. Dulles Transit Partners, the design-build consortium owned by Bechtel Infrastructure Inc. and Washington Group International, expects that phase to be completed in 2013. Completion of the Silver Line to the airport and Loudoun County is slated for 2015, although the funding strategy for phase two is not finalized.