The Dulles Corridor Metrorail Project is a new 23-mile extension of the current Metrorail system, branching from the Orange Line's East Falls Church Station in Arlington, Virginia to the Washington Dulles International Airport and west to eastern Loudoun County. The project added 11 stations, and it includes the construction of a new rail yard on Dulles Airport property and procurement of 128 railcars. Upon completion of the project, operation will be transferred to the Washington Metropolitan Area Transit Authority (WMATA).

Phase 1 of the project ran 12 miles from East Falls Church to Wiehle Avenue in Reston, Virginia. This phase includes five stations to the Silver Line, including four in Tysons Corner, Virginia. Phase 2 continued 11 miles from Wiehle Avenue to eastern Loudoun County, Virginia. This phase added six stations, including stops in Reston, Herndon, Dulles Airport, and Ashburn.

TIFIA financed direct loans to leverage the financial commitments made by Fairfax County, Loudoun County, and MWAA expediting the construction period, saving $2.3 billion in financing costs, and decreasing the extent of planned future toll rate rises. The extension will improve transportation to the area’s largest employment centers in Virginia (Tysons Corner, Reston/Herndon region), as well as provide a one-seat ride from the Airport to downtown Washington, DC. According to the Project Sponsors, the project is forecasted to achieve transportation and mobility benefits including the elimination of approximately 402 million vehicle miles travelled per year, over 300 tons of harmful auto emissions, and travel time savings of approximately 53 minutes per trip. The project is also expected to facilitate substantial transit-oriented development and job growth that will contribute approximately $1.2 billion in total economic impact and help to transform Tysons into a walkable, sustainable, urban center that Fairfax County estimates will be home to up to 100,000 residents and 200,000 jobs by 2050.