The Silver Line of the Washington Metro in the United States consists of 28 existing and six planned rapid transit stations from Wiehle–Reston East to Largo Town Center. It has stations in Fairfax County and Arlington, Virginia, the District of Columbia, and Prince George's County, Maryland. Five stations are shared with the Orange Line alone, thirteen with both the Orange and Blue lines from Rosslyn to Stadium–Armory, and five stations shared with the Blue Line to both lines' eastern terminus at Largo Town Center. Only five existing stations are exclusive to the Silver Line, which began service on July 26, 2014.
The 11.7 miles (18.8 km) portion of the Silver Line between its split from the Orange Line and Wiehle–Reston East station is in Fairfax County, Virginia and was constructed as Phase 1 of the Dulles Corridor Metrorail Project.  Phase 2 will expand the line another 11.5 miles (18.5 km) to Loudoun County via Washington Dulles International Airport and add six stations to the line. Preliminary construction of Phase 2 began in 2014 and is scheduled to open in 2020.      The $6.8 billion project is the largest expansion by route mileage since the inception of Metro in 1976.  
The Silver Line has two primary goals. The first is to link Washington, D.C. by rail to Washington Dulles International Airport and the edge cities of Tysons Corner, Reston, Herndon, and Ashburn. The second is to spur urban development in Tysons Corner and reduce overall reliance on highway traffic in the business district, Virginia's largest and the 12th-largest in the country. The district's area is comparable in size to downtown Washington, D.C., but is rather insulated from its surrounding neighborhoods and has no existing grid pattern in its streets.  The Silver Line would also improve public access to the Udvar-Hazy Center, an annex of National Air and Space Museum located near Dulles Airport; Virginia Regional Transit currently runs a shuttle bus from the airport to Udvar-Hazy. 
The pre-existing portions of the Silver Line, which became the Orange and Blue Lines, opened on July 1, 1977 from Stadium-Armory to Rosslyn, on December 11, 1979 from Rosslyn to Ballston, November 22, 1980 from Stadium-Armory to Addison Road, June 7, 1986 from Ballston-MU through East Falls Church and December 18, 2004 from Addison Road to Largo Town Center. Unlike all prior segments of the Metrorail system, which were designed and constructed by the Washington Metropolitan Area Transit Authority (WMATA), this line will be designed and constructed by the Metropolitan Washington Airports Authority (MWAA) and operated by WMATA. The first phase of the project is funded 43% by $900 million of federal funding, 28% by a special tax district on commercial property proximate to the Silver Line route and 28% by a $0.50 toll increase on the Dulles Toll Road.  Funding for the second phase of the project will be shared by Loudoun County, Fairfax County, the Commonwealth of Virginia and the MWAA. 
While the Silver Line was originally planned to terminate at Stadium-Armory, in 2012 the plan was changed for the line to end at Largo Town Center instead, because Stadium-Armory's pocket track is too short for trains to turn around. It follows the Blue and Orange Line tracks through DC, continuing through Arlington along the Orange Line and branching off immediately east of the West Falls Church station. The new tracks run in the median of the Dulles Connector Road to an elevated bridge, which takes them over Virginia Route 123. Two elevated stops along the west side of Route 123 serve the national headquarters of CapitalOne, SAIC and two enclosed Tysons Corner shopping malls. The tracks then enter a tunnel which emerges in the median of Virginia Route 7. Two elevated stations above Route 7 serve the western section of Tysons Corner. The elevated track then swings into the median of the Dulles Access Road until it reaches the airport. Along the way, five new stations would be built with platforms in the median of the access road and a faregate and pedestrian bridges to parking areas elevated above the highway. In anticipation of the Herndon station being built, in 1999 Fairfax County constructed a 1,750-space parking garage with ramps to the Dulles Access Road toll lanes and this facility is being used for bus commuters on an interim basis. The garage has drawn criticism because of alleged construction flaws. As originally planned, upon reaching the airport the track will enter a tunnel which will follow the path of the arrivals driveway of the airport terminal to a station located close to the terminal. The track would leave the tunnel near the airport hotel and economy parking lots and would head north parallel to the main runways. A storage yard and maintenance facility would branch off to the west occupying the airport's buffer zone north of the end of its major runways. The final two stops would be in the median of the Dulles Greenway, serving the Ashburn suburb.  Hence, the line is expected to draw both airport traffic and commuters from the far western suburbs of Washington, DC. Buses currently provide these users with limited public transportation. In contrast, the Silver Line is expected to provide trains once every six minutes during rush hours and once every fourteen minutes during non-rush hours. 
The federal government, which owned and operated Dulles Airport before Congress created the MWAA, built the Dulles Access Road in the 1960s to connect the airport to Washington by way of Interstate 66. As the access road was built, the government opted to reserve the median of the road for some form of rail transit,  and the nearby West Falls Church station was designed so that the line could eventually be extended in this direction. The original 1968 Metrorail plan included an eventual extension to Dulles airport.  In 1969, Senator William Spong of Virginia tried unsuccessfully to have the extension to Dulles be built as part of an early stage of the system rather than having it be built at some unspecified time in the future.  A 1971 study of the feasibility of Metrorail running to Dulles  estimated that 30,000 people would ride the extension each day. 
In 1995, the Virginia General Assembly authorized the Commonwealth Transportation Board (CTB) to provide for "additional improvements to the Dulles Toll Road and Dulles Access Road corridor... including, but not limited to, mass transit, including rail and capacity-enhancing treatments... from surplus net revenues of the Dulles Toll Road".
In 1998, Raytheon Engineers and Constructors proposed to build and operate a Dulles Corridor Bus Rapid Transit (BRT) system.  In January 1999, the Tysons-Dulles Corridor Group (which included Bechtel Corporation and West*Group) offered a competing BRT proposal that would ultimately extend the rail line to Ashburn.  These proposals prompted the Virginia Department of Transportation (VDOT) to evaluate the merits of BRT and heavy rail public transit in the corridor.
Local residents and officials had talked of a Metro extension to Dulles since the Washington Metro began service in 1976,  but significant planning did not begin until 2000. The Dulles Corridor Rapid Transit Project "scoping" process began in April 2000 with a series of meetings with local and federal officials, designed to collect the necessary authorities for the project. Local and federal law required extensive Analysis of Alternatives – the two most likely being bus lanes or inaction – and of the environmental impact. The rail-only line won over the other alternatives. Initial environmental hearings, which closed on August 28, 2002, were positive. Although planners originally considered ending the first phase at Tysons Corner, state officials decided that the first phase would end at Reston's Wiehle Avenue, partially to reassure the Metropolitan Washington Airports Authority that the line would eventually run to Dulles Airport.  The project received formal approval on June 10, 2004. 
In February 2005, the CTB approved a 50 cent increase in the Dulles Toll Road toll rates, effective May 22, 2005, and "reaffirm[ed] that no less than 85 percent of existing surplus Dulles Toll Road net revenues shall be dedicated for mass transit and rail in the [Dulles] Corrdor" and provided "that all additional toll revenue generated from the May 22, 2005 toll adjustment shall be dedicated to the [Metrorail] Project." Between July 1, 2003, and November 1, 2008, when the toll road was transferred to MWAA, over $138 million in net surplus toll revenue (together with accumulated interest) was provided to MWAA for the Silver Line project. 
Although the original financing plan called for a 50-cent toll increase on the Dulles Toll Road to finance the Silver Line (25 cents at the main plaza and 25 cents at the ramp plazas), the increase in projected costs resulted in the MWAA Board approving an increase in the surcharges. Effective January 1, 2010, the fare surcharge was increased to 50 cents at both the main plaza and ramp plazas, with additional 25-cent increases in main-plaza tolls set for 2011 and 2012.  These toll surcharges are designed to support MWAA's 52.6% share of the projected $5.25 billion combined cost of Phase I and Phase II. MWAA has justified these toll increases as necessary to meet an estimated $220 million in annual debt-service costs projected by 2020.  These toll revenue requirements were based on the assumption that the federal government, although it contributed $900 million to Phase I, would not contribute funds for Phase II. 
As a result of the surcharge increases, the toll in 2012 will be $2.25, or 16 cents per mile. The toll increase proposal drew 221 public comments and opponents outnumbered supporters by about 3 to 1. However, as the cost estimate grew from $5.25 billion to $6.8 billion, no final decisions have been reached to address the projected shortfall.
Tysons Corner tunnel dispute
Early plans called for a tunnel running from before the McLean station to beyond the Spring Hill station, with all four stations in between being below ground. When the contractor hired to design the Silver Line – a consortium of Bechtel and Washington Group International – found the costs to be too high, the design was changed to use a short tunnel, running only between the Tysons Corner and Greensboro stations (underneath higher ground) with all four stations being at or above ground. In March 2006, the contractor was ordered to examine an alternative "large bore" tunnel digging technique (successfully used in Europe) with the potential to lower costs of a tunnel through the entire Tysons section. The contractor found that there would not be a significant cost reduction and proposed staying with the short tunnel option.
After allegations that the design contractor had inflated costs for the tunnel in order to avoid sharing the job with an outside tunneling contractor, the long tunnel concept was revived in April 2006. The allegations led to calls for an outside cost estimate to determine more realistic tunnel costs. On May 15, 2006, Virginia Transportation Secretary Pierce R. Homer announced the creation of an advisory panel headed by the American Society of Civil Engineers. The panel had about two months to evaluate options for completing the line through Tysons Corner, with the results presented to the state on July 27, 2006 and published on July 31, 2006. 
On September 6, 2006, Virginia Governor Tim Kaine announced his decision in favor of an elevated track through Tysons Corner. In his statement, Kaine said he believed a tunnel would be the best option, but decided against it, citing a fear of losing federal funding for the project.
Shortly after Governor Kaine's decision, the Greater McLean Chamber of Commerce formed a coalition of tunnel supporters, called Tysons Tunnel, Inc. and put forth a technical proposal to help revive consideration of building a tunnel through Tysons Corner. The Virginia Department of Rail and Public Transportation hired an independent consultant to assess the coalition's proposal. However, the consultant's report – sent to Secretary Homer on March 7, 2007 stated that "[t]here is a significant risk that the project cost of a Large Bore Tunnel would not meet the Federal Transit Administration's (FTA's) cost-effectiveness ratio criteria, which could compromise federal funding for the project".  
On November 26, 2007, Tysons Tunnel, Inc. filed a lawsuit against the United States Department of Transportation and the FTA in the Eastern District of Virginia challenging the denial of their petition to reopen and consider additional evidence regarding the benefits of a tunnel over the aerial option. Gary Baise, the Republican challenger to Gerry Connolly's Fairfax County Board of Supervisors Chairmanship, represented Tysons Tunnel.  By 2010, Tysons Tunnel, Inc. ceased operations. 
Start of construction was delayed as approval of the $900 million federal contribution to project costs awaited the conclusion of FTA's review of the proposal submitted by Virginia. Virginia government representatives, including Governor Tim Kaine and U.S. Senators John Warner and Jim Webb, arrived at the FTA on January 24, 2008 to address last minute concerns by FTA staff and administrators. FTA Administrator James Simpson presented Governor Kaine with a letter that contained stark criticisms of the project as presented. The project as presented was given a "medium–low" rating (projects must receive a "medium" or higher rating to be approved under the Federal New Starts Funds project) and determined ineligible to receive the $900 million in federal funding. FTA's concerns included the Metropolitan Washington Airports Authority's inexperience in large design-build contracts, an exaggeration of funding numbers from the Dulles Toll Road and an inability for Metro to maintain the 23-mile (37 km) line once it had been built. Virginian leaders vowed to address the concerns by January 28, 2008, as several fixed price contracts for building materials costs were due to expire on February 1.   Governor Kaine requested an extension of the deadline to February 1, which was granted by the FTA. 
On April 30, 2008, the FTA reversed the earlier decision and approved the above-ground project, saying that it met standards for cost efficiency, construction and ridership, moving it closer to receiving the $900 million in federal funding. Officials told The Washington Post that the project would move into the final design stage. The FTA approved funding for the project on December 4, 2008.
On March 10, 2009, U.S. Transportation Secretary Ray LaHood signed the formal agreement that awarded the $900 million promised by the federal government for construction of the Silver Line, with major construction expected to begin in several weeks. Utility relocation work started at Tysons Corner in mid-2008.
MWAA planned to award a separate design-build contract for Phase II. The Phase II contract was awarded in May 2013 and the projected completion date was to be in 2018.  However, it was later extended to 2019 or 2020. 
Although construction was planned to begin in 2005, the delays in approval of funding pushed back the start date. To facilitate Silver Line construction, responsibility for the project was transferred on November 1, 2008, from the Virginia Department of Transportation (VDOT) to the MWAA. Utility relocation work began in 2008, and construction began on March 12, 2009.  
The extension runs in its own right-of-way on a route similar to that of the Dulles Access Road, running both at grade and via aerial structures. The only significant diversions from the access road route are for the stops in Tysons Corner and at Dulles International Airport, where the Metro is currently planned to alternate between subway and elevated track to maintain the exclusive right-of-way.
Service on Phase I of the Silver Line opened on July 26, 2014 between Wiehle – Reston East and Largo Town Center, with five new stations being added to the existing network west of East Falls Church. The full line to Ashburn, including a station at Dulles International Airport, is expected to be completed in 2018. 
One lane of southbound Virginia Route 123 in Tysons Corner was closed for a two-year period, starting on February 22, 2010, for construction of the McLean Metro station. The distance impacted was two blocks, from Scotts Crossing Road to the Capital Beltway. 
When the Orange Line was originally constructed in 1977, foundations for the bridges to carry the Silver Line over I-66 to the median of the Dulles Access Road were built up to ground level. These foundations included steel piles that were driven into the ground and capped with concrete. However, detailed records for these original foundations were lost. As a result, engineers asked for the foundations to be inspected by digging around them to determine the condition of each pile under the concrete foundation caps.
Some of the foundations are located in confined spots adjacent to I-66 and the electrified third rail of the Orange Line, making access difficult. Dulles Transit Partners offered to inspect seven foundations that were easily accessible, but the FTA insisted that all foundations be tested. Dulles Transit Partners and MWAA agreed to test all foundations before the bridge piers were built upon them. This required the portion of the Orange Line between the West Falls Church and East Falls Church Metro stations to be taken out of service on weekends while the tests were conducted. The foundations were acceptable and the bridge construction proceeded using the existing foundations.
There has been controversy over the contract between the MWAA and Dulles Transit Partners, which consists of Bechtel and Washington Group International. The $2.7 billion project was originally awarded by VDOT under the Virginia Public-Private Partnership Act, rather than by using conventional competitive bidding based upon a detailed specification. As a result, the contractor is allowed to both design and build the project with no upper cap on its cost. Problems could arise from the arrangement where MWAA is supervising the design and construction but ultimately WMATA must operate the Silver Line. The contract provides for price escalation of $3 million to $6 million a month for delays. VDOT transferred the contract to MWAA when MWAA took over the project in November 2008.
Opening of Phase I
The original schedule planned for revenue service to begin in 2013. The contractor reported to MWAA on February 7, 2014, that construction was complete. MWAA had fifteen days to review the documentation and decide whether it agreed, but on February 24 they announced that the contractor had failed to meet seven of twelve criteria outlined in the contract.
On March 19, 2014, MWAA announced additional delays in the project due to public address speakers and a communications cable that did not meet code and did not offer a new completion date. They hoped to turn it over to WMATA by April 9, 2014.  WMATA requires an additional 90 days for testing and training.  The system then underwent 90 days of testing and staff training. This suggested, at the time, that the line could open as early as July 4, 2014.  On May 27, 2014, WMATA was handed over control of the line, with service to begin "within 90 days".  Finally, on June 24, 2014, it was revealed that the official opening date for the first five stations had been set for July 26. 
After a set of speeches and announcements prior to opening, which were televised on local cable television station News Channel 8, and attended by the Governor of Virginia, Terry McAuliffe, Metro General Manager Richard Sarles, the entire Metro Board of directors, District of Columbia Mayor Vincent C. Gray, and other regional politicians, a ribbon cutting took place at the Wiehle – Reston East, and shortly after noon on July 26, 2014, the five new stations were opened for passenger service.  
Although the Silver Line attracted riders, its average weekday boarding was 17,100 during its first year of operations instead of the projected 25,000 riders.
Effect on the Metro map
Metro's iconic rail map, in distribution since Lance Wyman and Bill Cannan (Wyman & Cannan) designed it in 1976, takes – according to some observers – a "pop art" approach to representing its subway network.  The Metro rail map uses unusually "thick" strokes to mark its radial lines. To fit in the current space and make use of the iconography as currently proportioned, the map relies upon the fact that no more than two lines overlap at any single location.  The addition of the Silver Line creates a three-line overlap from Rosslyn to Stadium-Armory, a fact that led WMATA to publicly announce in 2010 that it was considering a new map design.  A number of unofficial attempts by graphic designers to redraw the Washington Metro map to include the Silver Line have done so by thinning the strokes throughout. 
In 2003, predating Booth's attempt, WMATA released a professionally designed graphic that displayed the Silver Line on an unofficial map that resembled the current version, but with thin lines. The interplay between Metro's unofficial proposal and those of other designers received attention in a number of press outlets.   A poster displaying a map of similar design has been hanging in DC Councilman Jack Evans' office for a number of years, but received scant attention until 2008.  Wyman, one of the original designers of the map, was confirmed as the layout specialist who would be redesigning the map by the Washington Post on June 4, 2011.
A thick-line version of the map, released as part of Metro's Rush Plus plan, showed the Silver Line spurring off the Orange Line between the Ballston and East Falls Church stations in a northwesterly direction, with five unlabeled stops (the Phase I stations).  The final map released for the Silver Line's Phase I opening features the stations shared by the three lines as normal stations, with the dots signifying stations located on the colored line in the center and small white stubs extending from the center dots into the adjoining colored lines. 
Phase II Dulles extension
While construction of Phase I to Wiehle – Reston East was under way, the funding and planning of Phase II through Dulles Airport continued. This included the adoption of a special taxing district by the Town of Herndon and a public planning forum. Early cost estimates for Phase II had been $2.75 billion; however, a group of consultants increased the estimate in 2010 from $3.44 billion to $4.1 billion.
On April 6, 2011, the MWAA Board voted 9 to 4 to build an underground station located 550 feet (170 m) from the airport terminal rather than an above-ground station 1,150 feet (350 m) away from the terminal. The underground station would be more convenient to travelers, but would come at an additional cost of $330 million and would extend the construction time of the project, delaying the expected opening to mid-2017. Former Virginia Governor Bob McDonnell opposed the decision to build a more expensive underground station and threatened to withhold support for the project. U.S. Secretary of Transportation Ray LaHood offered to mediate the dispute. On March 7, 2012, the projected $3.8 billion cost for Phase II was reduced to $2.7 billion with the elimination of the underground station at Dulles Airport and other cost savings. 
The extension of the Silver Line to Dulles and Loudoun County was in jeopardy until July 3, 2012, when the Loudoun County Board of Supervisors voted 5-4 to extend the line to Dulles Airport and into the county. 
On April 25, 2013, the Phase II contract was issued at a cost of $1.177 billion.  On August 20, 2014, the United States Department of Transportation announced that Phase II would be funded with a $1.28 billion Transportation Infrastructure Financial Innovation Act (TIFIA) loan. This delivers part of an approximately $1.87 billion combined commitment of TIFIA loans for Phase II, which represents the largest TIFIA assistance for a single project in the program's history. 
By July 2016, 30% of the Phase II project had been completed. The contractors reported that significant progress was made with regard to the structure of the line. 
By March 2017, completion of Phase II construction had reached 56% with work on the rail yard at Dulles Airport reaching 46%, 76% of deck spans being poured, and all aerial guideway girders over the Dulles Access Road near Saarinen Circle being set in place. MWAA reported that crews would soon begin installation of pedestrian bridges at the five stations under construction in the median of the Dulles Access Road and the Dulles Greenway. 
List of stations
|Station||Code||Opened||Other Metro Line(s)||Notes|
|Ashburn||N12||2020 (projected) ||Future western terminus Planning names: Route 772, Ryan Road|
|Loudoun Gateway||N11||2020 (projected) ||Planning names: Route 606, Morgan Road|
|Washington Dulles International Airport||N10||2020 (projected) |
|Innovation Center||N09||2020 (projected) ||Planning names: Route 28, Herndon – Dulles East|
|Herndon||N08||2020 (projected) ||Planning names: Herndon–Monroe, Herndon – Reston West|
|Reston Town Center||N07||2020 (projected) ||Planning name: Reston Parkway|
|Wiehle–Reston East||N06||2014||Current western terminus Planning name: Wiehle Avenue|
|Spring Hill||N04||2014||Planning names: Tysons West, Spring Hill Road|
|Greensboro||N03||2014||Planning names: Tysons Central 7, Pike Seven|
|Tysons Corner||N02||2014||Planning names: Tysons Central 123, Tysons Center|
|McLean||N01||2014||Planning names: Tysons East, Tysons McLean, West Park|
|East Falls Church||K05||1986|| ||Transfer station for the Orange Line (Western)|
|Virginia Square–GMU||K03||1979|| |
|Court House||K01||1979||Orange Line|
|Rosslyn||C05||1977||Orange Line Blue Line||Transfer station for the Blue Line|
|Foggy Bottom–GWU||C04||1977||Orange Line Blue Line|
|Farragut West||C03||1977||Orange Line Blue Line|
|McPherson Square||C02||1977||Orange Line Blue Line|
|Metro Center||C01||1976||Orange Line Blue Line Red Line||Transfer station for the Red Line|
|Federal Triangle||D01||1977||Orange Line Blue Line|
|Smithsonian||D02||1977||Orange Line Blue Line|
|L'Enfant Plaza||D03||1977||Orange Line Blue Line Yellow Line Green Line||Transfer station for the Yellow and Green Lines|
|Federal Center SW||D04||1977||Orange Line Blue Line|
|Capitol South||D05||1977||Orange Line Blue Line|
|Eastern Market||D06||1977||Orange Line Blue Line|
|Potomac Avenue||D07||1977||Orange Line Blue Line|
|Stadium–Armory||D08||1977||Orange Line Blue Line||Transfer station for the Orange Line (Eastern)|
|Benning Road||G01||1980||Blue Line|
|Capitol Heights||G02||1980||Blue Line|
|Addison Road||G03||1980||Blue Line|
|Morgan Boulevard||G04||2004||Blue Line|
|Largo Town Center||G05||2004||Blue Line||Current eastern terminus|