page_title: Silver Line (MBTA)
section_title: Waterfront development
hierarchical_section_title: Silver Line (MBTA) / History / Waterfront development
caption_attribution_description: English: Silver Line trolleybuses at Courthouse station in 2005
context_page_description: The Silver Line is a system of bus routes in Boston and Chelsea, Massachusetts, operated by the Massachusetts Bay Transportation Authority (MBTA). It is operated as part of the MBTA bus system, but branded as bus rapid transit as part of the MBTA subway system. Six routes are operated as part of two disconnected corridors. As of 2019, weekday ridership on the Silver Line was 39,000.
  The four Waterfront routes operate out of an underground terminal at South Station and run through the South Boston Piers Transitway – a dedicated bus tunnel through the Seaport District with stations at Courthouse and World Trade Center. At Silver Line Way, they fan out on the surface: the SL1 to Logan International Airport, the SL2 to Design Center, and the SL3 to Chelsea via East Boston. An additional short turn route, SLW, runs only at peak hours between South Station and Silver Line Way. The Waterfront routes use articulated dual-mode buses that operate as electric trolleybuses in the Transitway and conventional diesel buses on the surface. Two routes operate on Washington Street between Nubian station and Downtown Boston.
context_section_description: For most of the 20th century, the Seaport District was an industrial area occupied by rail yards and wharves; the South Boston Army Base and South Boston Naval Annex were served by short bus routes that connected with the Red Line at South Station. After the military bases closed in 1974 and the rail yards were no longer needed, the Seaport was designated for commercial development, with accompanying need for expanded transit. The MBTA conducted a feasibility study in 1987 and released a Draft Environmental Impact Report (DEIR) in 1989. The DEIR selected an underground "transitway" over alternatives including a surface light rail line, an elevated people mover, a commuter rail shuttle, and a relocation of the Red Line. The transitway was to use trolleybuses or dual-mode buses, rather than the light rail and people mover possibilities considered; it would connect with the Red Line at South Station, the Orange Line at Chinatown, and the Green Line at Boylston. Costs could be reduced by combining its construction with the upcoming Central Artery/Tunnel Project ("Big Dig"). Service from the transitway could be extended to serve Logan International Airport, to form part of a proposed circumferential transit line, and to connect with the planned Washington Street service.
  The South Boston Piers Transitway alignment was refined by the Draft Environmental Impact Statement (DEIR) in 1992. The Final Environmental Impact Statement/Final Environmental Impact Report (FEIS/FEIR) was approved in December 1993. The South Station–Seaport segment was to open in 2000, with the Boylston segment opening in 2006. The stations at World Trade Center, Courthouse, South Station, Chinatown, and Boylston would each have island platforms, and the tunnel could be later converted to light rail as a Green Line branch if needed. Daily ridership was expected to be between 24,200 and 37,200 for the first phase, and between 34,800 and 69,800 for the full build, depending on the rate of commercial development. In November 1994, the Federal Transit Administration (FTA) agreed to fund $331 million (80%) of the $413 million first phase, which was to be completed in December 2000. The environmental approval process was completed in April 1995.
  In 1997, with construction on the transitway already under way, Massport cancelled a planned people mover at Logan Airport in favor of dual-mode buses operating from the transitway and through the newly-opened Ted Williams Tunnel. A connector road was to extend the transitway from D Street to Haul Road. These changes were approved in February 1998. In May 1999, the MBTA indicated plans to through-route the transitway with the planned Washington Street service as the "Silver Line", with the Washington Street service as Phase I, the initial Transitway build as Phase II, and the Boylston extension as Phase III.
  Initial construction of the Transitway was divided into four main sections: South Station and turnaround loop plus 1,550 feet (470 m) of tunnel ($96 million), Russia Wharf and Fort Point Channel tunnel ($128 million), Courthouse station plus 1,450 feet (440 m) of tunnel ($110 million), and World Trade Center station plus 1,200 feet (370 m) of tunnel ($43 million). The Russia Wharf section, using the New Austrian tunnelling method, was the most technically complex; ground freezing was required to support the historic Russia Wharf Buildings. It also included an immersed tube under the Fort Point Channel. The discovery of a massive boulder under the Channel delayed the project by a year. By late 2000, the project was three years behind schedule and almost $200 million over budget; the MBTA diverted $150 million of other federal grants and $50 million of contingency funds to cover the costs. The Transitway was ultimately completed in 2004, with a final cost to the MBTA of $624 million. Although some projects like the new federal courthouse and the new convention center had been built, commercial development had lagged early plans; the MBTA adjusted its 2006 daily ridership projections from 45,000 to 14,000 shortly before 
caption: A 40-foot Silver Line trolleybus at Courthouse station in 2005. These buses were briefly used until the dual-mode buses entered service.
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