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Silver Line (MBTA)

The Silver Line is a bus rapid transit (BRT) system 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 part of the MBTA subway. Six routes are operated as part of two disconnected corridors. As of 2019, weekday ridership on the Silver Line was 39,000.

MBTA Silver Line
MBTA route SLW bus approaching World Trade Center station, March 2017.JPG
A Silver Line bus approaching World Trade Center station
ParentMassachusetts Bay Transportation Authority
FoundedJuly 20, 2002 (Washington Street)
December 17, 2004 (Waterfront)
LocaleBoston and Chelsea, Massachusetts
Service typeBus rapid transit
Stops14 (Washington Street)
21 (Waterfront)
HubsSouth Station, Dudley Square
Fleet24 (Washington Street)
32 (Waterfront)
Daily ridership39,000 (Q2 2019)[1]
Fuel typeDiesel hybrid (Washington Street)
Dual-mode diesel/trolleybus (Waterfront)
WebsiteMBTA - Bus

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 SL1 and SL3 operate in mixed traffic through the Ted Williams Tunnel; the SL3 uses a limited-access haul road in East Boston and a dedicated busway in Chelsea for part of its route. The SL2 operates in mixed traffic in the Seaport. The Waterfront routes use articulated dual-mode buses that operate as electric trolleybuses in the Transitway and conventional diesel buses on the surface. Battery electric buses and a diesel hybrid bus with extended battery range are being tested; one of the types may ultimately replace the dual-mode buses.

Two routes operate on Washington Street between Dudley Square in Roxbury and Downtown Boston. The SL5 terminates at Downtown Crossing and the SL4 on the surface at South Station. The two routes operate mostly in dedicated lanes on Washington Street and Essex Street, though sections in Downtown Boston and Dudley Square operate in mixed traffic. They use articulated diesel hybrid buses, which replaced compressed natural gas (CNG)-powered buses in 2016-17.

The Washington Street corridor was built to replace the Orange Line rapid transit line, which was moved from the Washington Street Elevated to the Southwest Corridor in 1987. Initial plans called for a light rail line operated as part of the Green Line, but trolleybuses and later CNG buses were substituted. Service improvements to the route 49 bus began in 2001, and the Silver Line brand was introduced on July 20, 2002. The articulated CNG buses began operation in 2003. On October 13, 2009, the SL4 began service and the original route was designated SL5.

Planning began in 1987 for mass transit to serve the growing Seaport; a new transit tunnel called the South Boston Piers Transitway was chosen in 1989. It was to run from Boylston to World Trade Center via Chinatown and South Station, though the Boylston-South Station section was later deferred as a separate phase. After years of delays, service through the $624 million Transitway began on December 17, 2004. SL2 and SL3 service began on December 31, 2004, with the SL1 added on June 1, 2005. The original SL3 route to City Point was discontinued on March 20, 2009. A separate SL3 route to Chelsea - originally planned as part of the cancelled Urban Ring Project - began service on April 21, 2018.

In 1999, the MBTA designated the Washington Street and Transitway projects as the Silver Line, and planned for the Boylston tunnel extension to include a portal to Washington Street for through-running. The connecting tunnel from Washington Street to Boylston was designated as Phase III and originally . After several design changes, by 2005 Phase III was expected to cost around $800 million; projected completion had been delayed from 2006 to 2010, then to 2013. The project was placed on hold in 2005; planning resumed in 2006 after the controversial portal was relocated. However, the project cost rose to $2.1 billion, and it was cancelled in 2010. Several other Silver Line extensions have been proposed, as has a conversion of the Washington Street corridor to light rail, but most have not been pursued.

The Silver Line has been the target of criticism by riders and transportation planners. The choice of BRT rather than light rail on Washington Street was viewed by Roxbury residents as a deliberate slight, leading to the nickname of "The Silver Lie." Much of the Silver Line is missing BRT Standard features such as enforced dedicated lanes, off-vehicle fare collection, sheltered stations, and transit signal priority; a 2011 report by the Institute for Transportation and Development Policy (ITDP) called the Silver Line "Not BRT". Because the Transitway was not originally designed for service to Logan Airport or Chelsea, it does not have a direct connection to the Ted Williams Tunnel. A normally-unused ramp would shorten the outbound routing by 0.7 miles (1.1 km); after years of controversy, MassDOT agreed in 2019 to allow limited use of the ramp.


Waterfront: SL1, SL2, SL3Edit

Waterfront routes
  Terminal B Stop 2
Terminal B Stop 1  
  Terminal C
Terminal A  
  Terminal E
Design Center
88 Black Falcon Avenue
Drydock Avenue &
Black Falcon Avenue
27 Drydock Avenue
Bellingham Square
23 Drydock Avenue
Box District
Eastern Avenue
Northern Ave & Tide St
Northern Ave & Harbor St
Silver Line Way
World Trade Center
South Station
 SL1  SL2  SL3  SLW 

Three Silver Line services operate from South Station in a dedicated tunnel, the South Boston Piers Transitway, serving the underground Courthouse and World Trade Center stations in the Seaport District then splitting at the Silver Line Way surface station.

  • SL1 Logan Airport – South Station
  • SL2 Design Center – South Station
  • SL3 Chelsea – South Station

During rush hours, additional short turns (designated SLW) are run between South Station and Silver Line Way to increase frequency in the Transitway.

Route SL2 runs on Northern Avenue, then on a one-way loop on Drydock Avenue and Black Falcon Avenue with multiple stops serving the Innovation and Design Building and the Flynn Cruiseport Boston. The route serves the loop in two different patterns. Before noon, outbound buses proceed around the whole loop, lay over at the Design Center stop, then proceed inbound. After noon, outbound buses make a shorter western loop, lay over at Design Center, then proceed inbound via the main loop.[2] From Silver Line Way, route SL1 and SL3 buses loop backwards on Haul Road, then cross under Boston Harbor in the Ted Williams Tunnel to East Boston. Route SL1 loops around the Logan International Airport terminals, with stops at the arrivals level of each terminal (including two separate stops at lengthy Terminal B). Route SL3 serves Airport station, follows the Coughlin Bypass Road, and crosses Chelsea Creek on the Chelsea Street Bridge. It then follows a dedicated busway to Chelsea, with intermediate stops at Eastern Avenue, Box District, and Bellingham Square.[3] The three Transitway stops are full rapid transit stations; the Chelsea busway stations have large concrete shelters, while most other surface stops have small shelters.[4]:10

The Waterfront routes have regular rapid transit fares.[5]:13 Passengers enter through faregates at the three Transitway stations, and pay at the on-board farebox at all other stops.[4]:12 Fares are free when boarding at the Logan Airport stops.[5]:31 (Inbound SL3 fares in Chelsea are also temporarily free during the Tobin Bridge/Chelsea Curves Rehabilitation Project, which is expected to last until late 2020.)[6] Transfer is possible to the Red Line within fare control at South Station. Normal transfers to other routes are available with a CharlieCard; transfers to/from the Blue Line at Airport and the Washington Street routes are available with a CharlieTicket.[5]:27

The Waterfront routes primarily use 60-foot (18 m) articulated buses with three doors, which provide greater capacity than standard 40-foot (12 m) transit buses. The dual-mode buses operate as electric trolleybuses (similar to the older Harvard-based trolleybus system) between South Station and Silver Line Way, and as conventional diesel buses on the surface branches.[7] The buses are low-floor and fully accessible, with kneeling bus technology and a wheelchair ramp at the front door. The 32 dual-mode buses, built by Neoplan USA, were delivered in 2004-05 and overhauled in 2014-18.[8][4]:11 Eight of the buses were funded by Massport and include luggage racks for airport passengers.[4]:11 All Silver Line buses are maintained at Southampton Street Garage.[7][9]:2.8

The existing dual-mode service pattern requires difficult-to-maintain dual-mode buses, and buses must make a time-consuming switch between modes at Silver Line Way.[10] Additionally, the overhead lines in the Transitway are difficult to maintain.[11] The MBTA has obtained several buses to test alternate options for Waterfront service. A single New Flyer diesel hybrid bus with extended battery range - sufficient to run through the Transitway on battery power - was obtained as an option on a separate order; it entered testing in September 2018 and revenue service in December. If that bus is deemed successful, the MBTA could order up to 45 similar buses.[12][13] On July 31, 2019, the MBTA began using five New Flyer battery electric buses on both Waterfront and Washington Street routes.[14]

Stop listingEdit

The power changeover at Silver Line Way
An SL2 bus on Black Falcon Avenue
An SL3 bus at Airport station
Neighborhood Station Routes Opened Transfers and notes
Financial District South Station SL1, SL2, SL3, SLW December 17, 2004   MBTA subway: Red Line, Silver Line SL4 route
  MBTA Commuter Rail: Framingham/Worcester Line, Needham Line, Franklin Line, Providence/Stoughton Line, Fairmount Line, Old Colony Lines, Greenbush Line, CapeFLYER
  MBTA Bus: 4, 7, 11
  Amtrak: Acela Express, Lake Shore Limited, Northeast Regional
  Intercity buses at South Station Bus Terminal
Seaport District Courthouse   MBTA Bus: 4
World Trade Center   Provincetown ferry
Silver Line Way Changeover point between diesel and overhead electric power
East Boston Terminal A SL1 June 1, 2005   Massport shuttles; MBTA Bus 171
Terminal B Stop 1   Massport shuttles; MBTA Bus 171
Terminal B Stop 2   Massport shuttles; MBTA Bus 171
Terminal C   Massport shuttles; MBTA Bus 171
Terminal E   Massport shuttles; MBTA Bus 171
Airport SL3 April 21, 2018   MBTA subway: Blue Line
  Massport shuttles; MBTA Bus 171
Chelsea Eastern Avenue   MBTA Bus: 112
Box District
Bellingham Square   MBTA Commuter Rail: Newburyport/Rockport Line
  MBTA Bus: 111, 112, 114, 116, 117
Chelsea   MBTA Bus: 112, 114
South Boston Northern Avenue & Harbor Street SL2 December 31, 2004   MBTA Bus: 4
Northern Avenue & Tide Street   MBTA Bus: 4
23 Drydock Avenue c. 2006[15][16] Relocated slightly from 21 Drydock Avenue in 2016[17]
27 Drydock Avenue December 31, 2004 Former stop at 25 Drydock Avenue closed in January 2016; relocated stop reopened in 2018.[18][19][20]
Drydock Avenue & Black Falcon Avenue Prior to January 2016, the stop was only used when buses skipped 88 Black Falcon Avenue at night and during poor weather. It was not shown on MBTA maps until 2018.[19][20]
88 Black Falcon Avenue Stop temporarily closed in April 2019 due to pier repair.[21] It will be permanently discontinued in late 2019 or early 2020.[22]
Black Falcon Avenue & Design Center Place Former SL2 stop closed in 2014
Design Center SL2   MBTA Bus: 4
Summer Street & Powerhouse Street Former SL3 stop closed on March 20, 2009
East 1st Street & M Street Former SL3 stop closed on March 20, 2009
City Point Former SL3 stop closed on March 20, 2009
Farragut Road April 9, 2005[23] Former SL3 stop closed on August 20, 2005

Washington Street: SL4 and SL5Edit

Washington Street routes
Downtown Crossing
  / Park Street
South Station 
Tufts Medical Center
Herald Street
East Berkeley Street
Union Park Street
Newton Street
Worcester Square
Massachusetts Avenue
Lenox Street
Melnea Cass Boulevard
Dudley Square

Two Silver Line route run between Dudley Square in Roxbury and Downtown Boston along Washington Street:

  • SL4 Dudley Square – South Station
  • SL5 Dudley Square – Downtown Crossing

These two route share most of their routing on Washington Street between Dudley Square and Tufts Medical Center, with dedicated lanes for most of the corridor and eight intermediate stops. North of Kneeland Street, the routes run on separate one-way loops. The SL5 runs north on Washington Street to Template Place (between Downtown Crossing and Park Street, with an intermediate stop at Chinatown. It returns south on Tremont Street, with a southbound stop at Boylston. The SL4 runs north on Washington Street to Chinatown, then east on Essex Street (with a dedicated lane) to a surface stop at South Station. It returns south on Surface Road and Kneeland Street.[3] Most stops have a canopy shelter with seating, maps, and a real-time arrival information display.[9]:2.5

The two routes have the same fare as local bus services (lower than rapid transit), with normal transfers with a CharlieCard.[5]:14 In recognition of their role as replacement for the Orange Line, transfers are also available with a paper CharlieTicket (which normally does not allow transfers).[5]:27 This was inherited from the previous route 49 bus, which had free transfers (with the flat token fare) to/from the Orange Line only at New England Medical Center.[9]:2.9

The Washington Street routes use 60-foot (18 m) diesel hybrid articulated buses with three doors, which provide greater capacity than standard 40-foot (12 m) transit buses.[7] The buses are low-floor and fully accessible, with kneeling bus technology and a wheelchair ramp at the front door. The routes use 21 New Flyer buses delivered in 2016-17 (part of a 44-bus order also used on routes 28 and 39), which replaced the original compressed natural gas (CNG) buses, plus three similar hybrid buses delivered in 2010.[7][24] All Silver Line buses are maintained at Southampton Street Garage.[7][9]:2.8

Stop listingEdit

An SL5 bus near Herald Street
Melnea Cass Boulevard, a typical Washington Street stop

All stops opened for Silver line service on July 20, 2002 unless otherwise noted.[23]

Neighborhood Station Routes Notes and connections
Roxbury Dudley Square SL4 and SL5   MBTA Bus: 1, 8, 14, 15, 19, 23, 28, 41, 42, 44, 45, 47, 66, 170, 171, 191
Melnea Cass Boulevard   MBTA Bus: CT3, 1, 8, 19, 47, 170, 171, 191
South End Lenox Street   MBTA Bus: 8, 170, 191
Massachusetts Avenue   MBTA Bus: 1, 8, 170, 191
Worcester Square Discontinued when the 49 was replaced by the Silver Line; restored in November 2002[9]:3.2
  MBTA Bus: 8, 170, 191
Newton Street   MBTA Bus: 8, 10, 170, 191
Union Park Street   MBTA Bus: 10, 191
East Berkeley Street   MBTA Bus: 9, 11, 191
Herald Street   MBTA Bus: 9, 11, 191
Chinatown Tufts Medical Center   MBTA subway: Orange Line
  MBTA Bus: 11, 43, 191
Chinatown   MBTA subway: Orange Line
  MBTA Bus: 11, 191
Downtown Boston Downtown Crossing SL5   MBTA subway: Orange Line, Red Line
  MBTA Bus: 7, 11, 501, 504, 505, 553, 554, 556, 558
At Park Street:   Green Line;   43, 55, 191, 192, 193
Boylston   MBTA subway: Green Line
  MBTA Bus: 43, 55, 191, 192, 193
South Station SL4 SL4 stop opened on October 13, 2009.[23]
  MBTA subway: Red Line; Silver Line SL1, SL2, SL3 routes
  MBTA Commuter Rail: Framingham/Worcester Line, Needham Line, Franklin Line, Providence/Stoughton Line, Fairmount Line, Old Colony Lines, Greenbush Line, CapeFLYER
  MBTA Bus: 4, 7, 11
  Amtrak: Acela Express, Lake Shore Limited, Northeast Regional
  Intercity buses at South Station Bus Terminal


Washington Street developmentEdit

Removal of the Elevated in 1987

The 1947 state act that created the Metropolitan Transit Authority (MTA) from the Boston Elevated Railway established four immediate projects for the new agency: extension of rapid transit to Braintree, expansion of the Tremont Street Subway to four tracks, replacement of the existing elevated lines (Charlestown Elevated, Causeway Street Elevated, and Washington Street Elevated) with subways, and an extension of the Cambridge-Dorchester Line northwest from Harvard.[25] In 1948, the legislature authorized the city to issue $19 million in bonds (equivalent to $162 million in 2018) to construct an extension of the Washington Street Tunnel under Shawmut Street, connecting with the existing elevated south of Dudley Square.[26] Although none of the proposals were built immediately, it established a precedent of replacing the elevated lines. In 1972, protests led to cancellation of the planned Southwest Expressway. Instead, the alignment was used for a combined corridor for intercity rail, commuter rail, and the Orange Line - replacing the Washington Street Elevated of the latter.[9]:3.1

The northern part of the new corridor was about 12 mile (0.80 km) west of Washington Street, so the MBTA began planning in 1978 for a replacement service between Dudley Square and Downtown Boston.[27][9]:3.1 By 1985, the MBTA favored bus or light rail service on Washington Street; the latter would have been a branch of the Green Line, operated through the 1962-abandoned southern branch.[28] The Orange Line was rerouted in 1987; that year, the UMTA rejected the MBTA's funding request to create a light rail line on the corridor.[9]:3.1 Local opinion favored the temporary retention of the northern portion of the Elevated until a permanent replacement could be built.[29] However, the MBTA closed the Elevated and instead upgraded the route 49 bus from a feeder route to a more frequent trunk route.[9]:3.1

The MBTA used this logo to advertise the Silver Line

In 1989, the MBTA announced that trolleybuses would be used on Washington Street, operating on 4-minute headways at peak hours.[9]:3.1 By 1990, the MBTA expected service to begin in 1993, with an underground connection to Boylston station and the proposed South Boston Piers tunnel in a future phase.[30] After several more years of studies, the MBTA decided in 1996-97 to build the route as a bus rapid transit line using compressed natural gas (CNG) buses to avoid the visual impact of overhead wires.[9]:3.2 Environmental documentation was filed in 1998, and construction began in 2001.[9]:3.2 The project cost $27.3 million, with major elements including $10.9 million for the 17 new buses, $10.9 million for road work, and $2.6 million for shelters.[9]:2.14 Planning and construction were combined with a necessary repaving of Washington Street, reducing costs.[9]:5.8 Intended for the route to equal the service quality of light rail, the MBTA branded it as the "Silver Line" and designated it equally to the existing MBTA subway lines on maps.[9]:4.11

The Silver Line followed largely the same route between Dudley Square and Downtown Boston as route 49; the primary change was stop consolidation.[23] (Although the MBTA considered other stop locations, most of the final stops were at existing route 49 stops.)[9]:3.3 The conversion to the Silver Line occurred in several steps. In December 2001, the MBTA opened a contraflow bus-only lane on Washington Street between Marginal Street and East Berkeley Street, allowing southbound buses to use Washington Street. This eliminated a longer outbound routing via Surface Road, and allowed an extension to a new downtown terminal at Template Place (between Park Street and Downtown Crossing stations). Service frequency was also increased at that time.[9]:1.2 On July 20, 2002, new Silver Line-branded CNG buses began operation - the first low-floor buses to operate in Boston - and the 20 stops were reduced to 11.[9]:1.2, 4.11 (In November 2002, a twelfth stop at Worcester Square was restored.)[9]:2.5 The 40-foot (12 m) were replaced by 60-foot (18 m) buses in August 2003, and service frequency was again increased.[9]:1.2 On January 31, 2005, the route was the first MBTA bus route to receive new automated fare collection equipment.[9]:2.9 By 2005, ridership was double that of route 49, but early decreases in travel time were cancelled out by longer dwell times.[9]:4.4, 5.1

Waterfront developmentEdit

A 40-foot Silver Line trolleybus at Courthouse station in 2005. These buses were briefly used until the dual-mode buses entered service.
Silver Line service plans as of 2005, showing the SL3 (discontinued in 2009) and the original SL4 and Phase III (never implemented)

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.[31] 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.[32]:1.1 The MBTA conducted a feasibility study in 1987 and released a Draft Environmental Impact Report (DEIR) in 1989.[33][4]:23 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.[32]:iii

The South Boston Piers Transitway alignment was refined by the Draft Environmental Impact Statement (DEIR) in 1992.[32]:V The Final Environmental Impact Statement/Final Environmental Impact Report (FEIS/FEIR) was approved in December 1993.[4]:24 The South Station-Seaport segment was to open in 2000, with the Boylston segment opening in 2006.[32]:2.81 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.[34][35] 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.[32]:4.26 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.[36]:1 The environmental approval process was completed in April 1995.[4]:24

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.[4]:24-25[37]:2.1 (Such use of the third harbor tunnel to run express bus service to the airport had been proposed as early as 1968.)[38] A connector road was to extend the transitway from D Street to Haul Road. These changes were approved in February 1998.[4]:25 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.[4]:25

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).[4]:15 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.[39] The discovery of a massive boulder under the Channel delayed the project by a year.[4]:15 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.[36]:4 The Transitway was ultimately completed in 2004, with a final cost to the MBTA of $624 million. (That figure includes the higher-than-expected cost of dual-mode buses, and part of the cost of the Southampton maintenance facility, but subtracts reimbursements from other projects.)[4]:16[36]:5 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 opening.[40]

The Transitway opened on December 17, 2004, with the Waterfront shuttle route between South Station and Silver Line operated by a mix of new dual-mode buses and trolleybuses borrowed from the Harvard-based routes.[23][4]:26 On December 31, 2004, service began on routes SL2 to the Boston Marine Industrial Park (BMIP) and route SL3 to City Point. Two days later, a Sunday-only Silver Line Way-Logan Airport shuttle service called "Silver Line Connector" began operation to meet a legal commitment to begin airport service that month.[23] The existing surface routes in the Seaport were discontinued or rerouted in January.[4]:5-7 Due to a lack of available dual-mode buses, CNG shuttles operated on the surface sections of the SL2 and SL3 routes from January 5 to March 14, 2005. On March 26, the two routes were combined on nights and weekends.[23] On April 9, weekday SL3 service was extended from City Point to a loop on Farragut Road.[23]

On May 28, 2005, the two routes were combined at all times as the SL2/3. This freed up buses for SL1 service to Logan Airport, which began on June 1.[23] As more buses entered service, the SL2 and SL3 were resplit into separate routes (except nights and weekends) on August 20, and the Farragut Road loop was cut due to noise complaints from residents.[41] On October 15, City Point service was cut on nights and weekends.[23] An SL4 route from South Station to Andrew station via the Boston Convention and Exhibition Center and D Street was planned to open in 2005, but was never implemented.[42][23] By 2006, the Silver Line had doubled transit ridership to the Seaport, and increased transit ridership to Logan by 24%.[4]:42, 44 The SL3 service was never successful, as the parallel route 7 route had a more direct route, lower fares, and better downtown connections. By 2008, the SL3 averaged less than one passenger per trip on the segment not shared with the SL2.[41] On March 20, 2009, SL3 service was cut, with SL2 service increased in its stead.[23] In October 2009, the SL2 terminus was renamed "Design Center" with no changes in service.[23]

Phase III plansEdit

Silver Line Phase III alternatives, showing the original 4 alignments plus the Charles Street Modified (CSM) alignment. The preferred route at the time of the project's cancellation was the CSM alignment (pink) feeding into the core tunnel (green).

The Boylston extension, as planned in 1993, would have run west from South Station under Essex Street, Avenue de Lafayette, and Avery Street. The Chinatown platform would have been under Hayward Place east of Washington Street, and the Boylston platform under the existing Green Line station, with a turnaround loop under Boylston Street and the Central Burying Ground.[37]:2.5-6 The 1999 decision to combine the Waterfront and Washington Street projects as the Silver Line resulted in the addition of a southern segment, likely using the same abandoned streetcar tunnel as had been proposed a decade before. A new underground station would have been built under Tremont Street, connecting to the existing New England Medical Center (NEMC) station, with a portal to Washington Street just north of Oak Street.[37]:2.5-7 In April 2000, the MBTA adjusted the alignment to use Boylston Street instead of Avenue de Lafayette and Avery Street, with side platforms at the stations. The new alignment would conflict less with development, provide a straighter route, avoid the need for a pedestrian crossing and a lengthy pedestrian tunnel at Chinatown, and move the Boylston loop away from the Burying Ground.[37]:2.8

In January 2002, the MBTA began seeking federal funding for 60% of the project cost. The Federal Transit Administration (FTA) approved the project for further planning than July.[4]:27 The Boston Regional Metropolitan Planning Organization rated the project as "high priority" in its May 2003 Program for Mass Transportation, citing its high estimated ridership, low operating cost and service to environmental justice neighborhoods.[43] In 2003, the preferred portal location was moved slightly north to avoid the need to demolish the YMCA building, and the NEMC station was removed.[37]:2.10-15 A proposal to consolidate the Chinatown and Boylsyon stations was rejected due to steep grades required and lack of cost savings, and a proposal to eliminate the loop was rejected because of the need to short turn most buses at Boylston.[37]:2.15-22 Further changes in 2003-04 were caused by the need to add a second platform at Boylston due to high expected ridership, and to reduce impacts to the historic Boston Common from the loop. One alternative placed the station and loop under Tremont Street south of Boylston Street; the other enlarged them under the Common.[37]:2.22-25

Continued concerns about the Common, concerns from Bay Village residents about impacts to Eliot Norton Park, and desires to add Back Bay service resulted in further changes in 2004-05. The platforms at Boylston were to be aligned east-west under Boylston Street west of Tremont Street, with the loop further to the west at Charles Street. New portal alignments were considered, including one on Columbus Avenue to the southwest.[37]:2.23-28 Capital cost was originally estimated at $768-812 million depending on the portal location; completion was moved from 2010 to 2013.[37]:3.38, 6.1 Daily ridership for the completed Silver Line system was estimated to reach 160,000 by 2025.[37]:3.33 In August 2005, the MBTA put the Phase III project "on hold" in order to build community consensus on a locally preferred routing.[44]

In February 2006, State Transportation Secretary John Cogliano proposed a $94 million plan that would eliminate most of the tunneling and cost of the original proposal while still connecting the two phases of the service.[45] Under Cogliano's plan, the Silver Line would run on the surface via Kneeland Street and Surface Road to a new tunnel portal on Essex Street near South Station. A fare-controlled shelter would be added at Downtown Crossing for routes still terminating there. The plan also included expansion of surface Silver Line service, with a new branch running from Copley Square into the Essex Street portal to provide a one-seat ride from the Back Bay area. The southern branch would be extended from Dudley to the Red Line stations at Mattapan via Blue Hill Avenue (replacing route 28) andAshmont via Washington Street (replacing route 23)[45] The plan was popular with Bay Village residents who had been worried about the full-length tunnel, but attracted criticism because it would not substantially speed travel times to downtown.[45]

Shelter at South Station for route SL4

A revised tunnel plan was put forward in March 2006, with support from most transportation leaders including Cogliano. The plan involved a variation of the Charles Street tunnel alignment, with the portal moved southwest onto Tremont Street near Marginal Road.[46][47][48] This "Charles Street Modified" alignment remained the preferred alternative for the remainder of the project. Contra-flow dedicated bus lanes, already in place on Washington Street, were to be extended onto Marginal Road and Herald Street to allow buses to reach the portal from the surface section.[49] On December 12, 2006, the FTA approved the project to re-enter its funding process.[4]:27 By mid-2008, environmental review and preliminary engineering were expected to be completed by the end of the year, with federal funding sought in 2010 and construction lasting from 2011 to a 2016 opening.[50][51]

However, the estimated price of the tunnel plan, dubbed the "Little Dig", had risen to $2.1 billion by May 2009.[52] The FTA assigned it a Medium Low overall rating, making it ineligible to move into the final design phase for federal New Starts funding. The Boston Region Metropolitan Planning Organization removed Phase III from the list of recommended projects in its long range plan because of funding limitations – a rapid turnaround from its "high priority" rating in 2003. Concluding that it could not successfully compete for more than one New Starts grant, MassDOT informed the FTA that it was no longer seeking New Starts money for Phase III. All New Starts funds available would instead be directed to the legally mandated Green Line Extension project. In a July 2010 report, the MBTA declared that Phase III was on indefinite hold and no further funds would be spent on the project.[53]

A partial solution that did not require a new tunnel opened on October 13, 2009, after expedited construction using federal stimulus money. The new route, SL4, covered much of the same alignment as the proposed Phase III, with a dedicated bus lane on Essex Street and a South Station stop west of Atlantic Avenue. The existing Downtown Crossing-Dudley route was renamed SL5 at that time.[54]

Extension to ChelseaEdit

Chelsea station in July 2018

The Urban Ring Project was a planned circumferential surface BRT line. It would have shared the Silver Line berths at Dudley Square, and have had a surface stop outside World Trade Center station, but otherwise would have been separate from the Silver Line.[55][56] The project was cancelled in 2010 due to high cost, but planning for several smaller sections continued.[57] The Chelsea-South Boston section was given high priority because Chelsea was densely populated yet underserved by transit.[57] MassDOT had also purchased the Grand Junction Branch - including abandoned sections in Chelsea and East Boston - from CSX Transportation in 2009, meaning that a potential right-of-way (which the urban Ring had proposed to use) was available.[57] A state study in 2011 analyzed potential Chelsea services, including a Silver Line branch or improvements to the route 112 bus.[57]

In 2013, MassDOT began public planning of the Silver Line Gateway. In addition to serving Chelsea, the proposed line would provide Blue Line riders a direct connection to the Seaport and South Station. Three possible alignments were studied. All used the Transitway and the Ted Williams Tunnel to reach Airport station, then the 2012-opened Coughlin Bypass Road to the Chelsea Street Bridge. The first alignment was to run entirely on a new busway on the Grand Junction right-of-way in Chelsea, with stops at Eastern Avenue, Box District, Bellingham Square (the Chelsea commuter rail station), and Mystic Mall. The second alignment option would have followed the Grand Junction to just short of the commuter rail station, then diverge onto surface roads to Bellingham Square, while the third alignment would have run entirely on surface streets, serving two stops on Central Avenue and four stops along a loop serving Chelsea station and the MGH Chelsea healthcare center.[58]

In September 2013, the MBTA indicated that it would pursue the first alternative, with an estimated daily ridership of 8,700, despite potential issues with bridge clearances and rebuilding the commuter rail station.[59] On October 30, 2013, MassDOT announced $82.5 million in state funding for the new Silver Line route to Chelsea, with completion expected in 2015. The announcement also included the relocation of the commuter rail station to Chelsea (Mystic Mall) and a $3 million, 34-mile (1.2 km) multi-use path from Eastern Avenue to Washington Street.[60] MassDOT awarded a $33.8 construction contract for the first phase of the project on September 17, 2014. That phase included the 1.3-mile (2.1 km)-long busway, the four Silver Line stations, replacement of the Washington Street bridge, and the Chelsea Greenway.[61]

Silver Line service to Chelsea (route SL3) began on April 21, 2018.[62] By October, daily ridership reached 6,200.[63] The second phase of the project includes the relocated Chelsea commuter rail station plus transit signal priority upgrades for the SL3. Construction began in August 2019, with completion planned for late 2021.[64]

Proposed future corridorsEdit

Southern branch of the Tremont Street Subway near the former Pleasant Street Portal. This tunnel was briefly considered for use in the Phase III tunnel and is the likely connecting route for a proposed conversion of the Washington Street section of the Silver Line to a branch of the Green Line.

Several other Bus Rapid Transit and express bus projects have been proposed in Boston, many under the Silver Line banner. The first two phases of the 2010-cancelled Urban Ring Project were to be BRT, with light or heavy rail for the final phase. The Urban Ring was considered a separate project, although it would have shared the SL1 route between Silver Line Way and Logan Airport.[43]

A number of Silver Line expansion corridors were considered in the 2003 Program for Mass Transportation (PMT); most were given brief consideration but not acted upon. One, a BRT express overlay for the route 28 bus (which runs from Ruggles station to Mattapan via Dudley), was revived in 2006 as part of Phase III plans. In 2009, the state proposed to replace the 28 bus entirely with a BRT route called 28X, including the installation of dedicated bus lanes, bus signal priority, and on-platform fare collection.[65] However, the proposal was withdrawn in 2010 due to local opposition, both to the design of the route and because the plan had been made with consulting local officials.[66] (In 2012, the Roxbury-Dorcester-Mattapan Transit Needs Study recommended the 28X bus to be implemented with no new infrastructure as an express bus adding additional trips to the corridor.)[67]

Several other corridors were considered in the 2003 PMT. These included a Dudley-Ashmont route replacing the route 23 bus (also revived in 2006 in Phase III planning, but not during the 28X proposal), as well as a new BRT tunnel to Kenmore with surface branches to the Longwood Medical Area via Brookline Avenue and Allston via Commonwealth Avenue, the Mass Pike, and Cambridge Street.[43][68] The City of Boston proposed an alternate western Silver Line branch using buses along the Mass Pike without a new tunnel, similar to existing express buses.[68]

The 2003 PMT included the possibility of converting the Washington Street section of the Silver Line to light rail (as had originally been promised) using the abandoned southern section of the Tremont Street Subway. The project was estimated to cost $374 million; ridership was estimated to be 34,000 daily riders almost entirely diverted from the Silver Line service. The project was given low priority, with the Phase III tunnel recommended instead.[68] In 2012, the Roxbury-Dorcester-Mattapan Transit Needs Study recommended the conversion to light rail as a long-term project, with the additional possibility of extending the line down Blue Hill Avenue to Mattapan along the route 28 bus corridor.[69]

In March 2019, state and local officials indicated plans to extend service from Chelsea on two routes to Kendall Square and to North Station, both via Sullivan Square. The routes would primarily use dedicated busways and bus lanes, although they may not be part of the Silver Line brand.[70]


Frequency and ridershipEdit

The SLW was one of three MBTA Bus routes to show a net profit in a 2012 study

The Silver Line routes are among the most frequent MBTA bus routes. All routes (except for the SLW shuttle) run at least every 15 minutes during all service hours, except for late evening service on the SL4. At peak hours, combined frequency on the trunk sections is about 30 buses per hour (2 minute headways) in each direction in the Transitway, and 12-14 buses per hour (4-5 minute headways) on Washington Street.[3][71] The routes have high ridership (though lower than many key bus routes) and low costs per rider compared to other bus routes in the MBTA system. In 2012, three routes (SL1, SL5, SLW) were the only MBTA bus routes to show a profit; the median net cost (after fares) on all MBTA bus routes was $2.13 per passenger.[72] In 2019, combined weekday ridership on Silver Line routes was 39,000.[1]

In addition to the public route name, the Silver Line and crosstown routes have internal route numbers in the 700 series. The SL5 is designated 749 after the 49 bus it replaced, while the other routes have similar numbers.[73]

Route # Rush hour headway Midday headway Weekend headway Weekday ridership (2018)[71]
SL1 741 8-9 minutes 8 minutes 8-12 minutes 8,132
SL2 742 5 minutes 10-12 minutes 15 minutes 6,420
SL3 743 10-12 minutes 15 minutes 12-15 minutes 6,200[63]
SLW 746 10 minutes (not available)
SL4 751 12 minutes 16 minutes 15 minutes 5,800
SL5 749 8 minutes 10 minutes 7-12 minutes 10,300


Mode choiceEdit

This is not bus rapid transit. All they did was take a diesel bus, change the engine, paint it silver and run it down the street through traffic.

Roxbury activist Bob Terrell[74]

When the Washington Street Elevated was replaced with the Southwest Corridor, MBTA promised "equal or better" surface transit on Washington Street to replace the Elevated.[45] Riders supported light rail; the decision to instead run buses was viewed as a broken promise and intentional disinvestment.[74][10] The Silver Line is substantially slower than the Elevated, with travel time from Dudley Square to Downtown Boston increased from 8 minutes to 20 minutes.[45] The Washington Street corridor population is poorer and less educated than the Southwest Corridor, and has a larger Black population; advocates including state representative Gloria Fox have called the poor service on the Silver Line racial discrimination against Roxbury.[74][75] Because of the poor service and the perception that the bus service was an inferior substitute for the originally-planned light rail line, advocates nicknamed the Washington Street service as the "Silver Lie".[74][76]

Two theoretical advantages of BRT compared to light rail are low cost and speedy implementation.[10]:6 However, Silver Line service did not begin Washington Street until 15 years after the Elevated came down; the first phase of the Transitway opened 15 years after the DEIR, and the second phase was never completed. The Transitway was built at "enormous cost"; it was the most expensive single BRT project in the world by a 2007 report.[10][77] Like the Downtown Seattle Transit Tunnel (which was later converted to light rail), the Transitway had comparable construction cost to light rail, but a lower level of service.[78] At the time of its cancellation, Phase III was expected to cost $2.1 billion - more than three times that of the Transitway.[52] Although transit ridership in the Seaport doubled after the introduction of the Silver Line, that growth is due partially to commercial development rather than the service quality.[10][76]

BRT qualityEdit

Red-painted bus lanes on an uncongested section of Washington Street
An SL1 bus waiting at the D Street light

Key features of bus rapid transit include dedicated lanes, frequent service, off-vehicle fare collection, sheltered stations, and intelligent transportation systems (ITS) features such as transit signal priority.[79]:99 A 2011 study by the Institute for Transportation and Development Policy (ITDP) determined that the Silver Line was best classified as "Not BRT" because it lacked many of these BRT Standard features.[10]

Off-board fare collection is only present at the three underground stops.[4]:12 A significant portion of delays on the surface sections are caused by long dwell times, as passengers only board through the front door to pay at the single farebox. On June 6, 2012, Massport began funding a three-month pilot of free fares from the five Logan Airport stops as an effort to decrease traffic congestion at the airport terminals.[80][81] Within the first month, average dwell time dropped by 20 seconds per stop.[82] Massport later extended the pilot until January 2013, then made free fares from Logan permanent.[83][84][5]:31 Stops on the Washington Street routes with more than fifteen passengers have an average dwell time over one minute, which affects both running time and reliability.[85] A two-week pilot program in 2017 tested all-door boarding on these routes, with free fares funded by a nonprofit. The pilot halved dwell times at busy stops, reduced overall average dwell time from 24 to 19 seconds, and increased reliability.[86][85] All-door boarding will be permanently implemented on all routes in the early 2020s as part of the AFC 2.0 fare system.[87]

The Washington Street routes have dedicated bus lanes between Herald Street and Melnea Cass Boulevard, as well as on Essex Street.[54][9]:2.1 However, these lanes are not physically separated from general traffic lanes and are designated as right-turn lanes at many intersections.[76][88] A lack of loading zones causes many vehicles to double-park in the bus lanes, and violations of the exclusive lanes are rarely enforced.[10][88] In the most congested parts of the corridor - Dudley Square and Downtown Crossing - no dedicated lanes are present.[76] Transit signal priority (TSP) was only planned for four locations on Washington Street. Due to conflicts between the MBTA, the contractors, and the city, the TSP equipment was not activated until 2006.[89][9]:2.10 Due to the lack of BRT elements, running times on the corridor show significant variability. Peak-hour times were as much as 1.7 times that of uncontested periods in 2006, indicating that the limited BRT elements on Washington Street were ineffective at actually speeding travel during congested periods.[76] Headway reliability is poor, largely due to operators failing to depart Dudley Square on time.[79]:136 Additional enforced downtown bus lanes, plus traffic restrictions on Temple Place and new loading zones in Chinatown, were added by the city in October and November 2019.[90]

Although the Transitway is a dedicated bus tunnel without interference from automobile traffic, Waterfront service is no faster than the on-street buses it replaced.[10] The tunnel was built for a maximum speed of 25 miles per hour (40 km/h); the narrow lanes without guided buses limit actual speeds to 15 miles per hour (24 km/h).[91][4]:31 Water leakage and poor drainage has damaged the concrete floor of the tunnel, leading to "poor ride quality".[11] The switch between electric and diesel power at Silver Line Way also represents a "significant delay".[10] Because the original Transitway design ended at D Street, buses must cross the street at a traffic light. A 2003 study indicated extending the Transitway tunnel under D Street ("T under D") for grade separation was feasible, with a cost around $75 million.[92] The light has attracted criticism from riders due to the delays it causes. A 2013 study found a median delay of 1.5 minutes per round trip at the light.[76][93]:136 In early 2016, the Boston Transportation Department modified the traffic light to use a fixed cycle, rather than relying on the detection of buses (only done during part of the cycle) to give a green light for the Transitway. However, the BTD's modifications did not modify the unusually-long 100-second cycle length nor actively prioritize buses, leading to criticism from transportation planners that the solution was inadequate.[94] Proposed air rights development over the station is required not to preclude later grade separation of D Street.[95] A gate and movable bollard near the light, which are used to prevent private vehicles from entering the Transitway, also cause delays to buses.[93]:141[96]

Although stop spacing varies widely between BRT systems, distances from 0.5 miles (0.80 km) to 1.0 mile (1.6 km) are typically recommended.[97] Even after dropping half the stops, the Washington Street corridor averages only 0.25 miles (0.40 km) between stops, with several stop spacings as low as 0.10 miles (0.16 km).[79]:102[9]:2.5 The Washington Street stops were built with open canopies; protected shelters were not added until 2010.[9]:5.8[98] A small traditional glass shelter is available at Temple Place; Boylston, Chinatown, and Tufts Medical Center have no shelters at all.[9]:3.2 Silver Line Way and the SL2 surface stops have glass shelters or none at all; the SL3 surface stops have canopies without shelters.[4]:10

Indirect routingEdit

The disputed ramp in 2017

Because the Transitway was not originally designed for service to Logan Airport or Chelsea, it does not have a direct connection to the Ted Williams Tunnel. Outbound SL1 and SL3 buses must travel 0.5 miles (0.80 km) west on Haul Road from Silver Line to access an eastbound ramp west of B Street, then travel east on a frequently-congested section of I-90. Inbound buses must exit I-90 at B Street and travel 0.3 miles (0.48 km) east on Congress Street to reach Silver Line Way.[3] An eastbound entrance ramp near Silver Line Way, normally restricted for use by Massachusetts State Police and MassDOT maintenance vehicles from an adjacent operations center, can shorten the outbound routing by about 0.7 miles (1.1 km). MassDOT claims the ramp was not designed by buses, though Fred Salvucci has claimed it was.[99] Outbound buses were temporarily allowed to use the ramp in 2006 after the Big Dig ceiling collapse, when there was no regular eastbound traffic through the tunnel.[100][4]:14 The Urban Ring was also proposed to use the ramp.[56] A 2010 study indicated that the ramp was safe to used for the Silver Line.[93]:163

Transit advocates have since pushed to allow use of the ramp by Silver Line buses ("Free the ramp"), though MassDOT claims the ramp is not safe to use when highway traffic is freely flowing.[101] The MBTA hired a consultant in 2018 to study potential use of the ramp.[99] In May 2019, MassDOT agreed to a limited test of ramp use, though advocates criticized MassDOT for limiting the test to only the evening peak hour, and only when highway speeds did not exceed 30 miles per hour (48 km/h).[102] The three-day test in August 2019 resulting in average time savings of 3-8 minutes per bus, with significantly larger time savings at the most congested times. After these results, MassDOT agreed to make modifications to the ramp entrance to eventually allow use of the ramp whenever traffic speeds are below 30 mph.[101]

Other issuesEdit

The SL3 route is subject to frequent delays due to the opening of the Chelsea Street Bridge – as many as ten times per day – for ships serving the upstream oil terminals. Each bridge opening causes a delay of up to 20 minutes, and the only alternate route involves a lengthy detour on Route 1A. Federal regulations give priority to marine traffic.[103] In December 2018, MassDOT officials sought to create a six-month pilot program to reduce peak-hour openings of the bridge, as well as the nearby Meridian Street Bridge used by the busy 116 and 117 bus routes.[63][104]

The CNG buses bought for the Washington Street service caused disruptive 35 Hz vibrations in nearby residential buildings.[105] It took a year to retrofit the fleet with new mufflers; during that time, older buses which did not have that problem were used at night.[9]:3.5


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