Blue Line (MBTA)

File:PostcardBostonMAEastBostonTunnel1906.jpg

The East Boston Tunnel under Boston Harbor was the first North American subway tunnel to run beneath a body of water when it opened in 1904,{{cite web |url=http://world.nycsubway.org/us/boston/blue.html |title=MBTA Blue Line|access-date=February 21, 2008 |work=NYCsubway.org}} and the second underwater vehicular tunnel of significant length built in the United States.{{rp|30}} The tunnel was constructed using a modified version of the Greathead Shield; {{convert|2700|ft|m}} of the {{convert|1|mi|km}} tunnel is actually under water.{{rp|30}} The excavation took two-and-a-half years, and cost $3 million and the lives of four workmen.{{rp|30}}

Initially used as a streetcar tunnel, it ran from Maverick Square in East Boston to downtown Boston's Court Street station, with an intermediate stop at Devonshire (now State). Court Street had pedestrian access to Scollay Square station (now Government Center) but transfers to the East Boston Tunnel required an additional fare of 1 cent. In 1906, Atlantic Station (now Aquarium) was opened, with a connection to the Atlantic Avenue Elevated. Court Street proved to be a problematic terminus as its single-track design limited frequent service.

File:Joy Street incline, 1915.jpg

The Boston Transit Commission (BTC) began construction of a {{convert|0.5|miles|adj=on|sigfig=1}} extension of the East Boston Tunnel on November 29, 1912.{{cite book |url=https://archive.org/stream/annualreportofbo19bost#page/46/mode/2up |title=Annual report of the Boston Transit Commission for the year ending June 30, 1913 |publisher=Boston Transit Commission |year=1913 |page=46 |via=Internet Archive}}{{cite book |title=Tremont Street Subway: A Century of Public Service |last1=Clarke |first1=Bradley H. |last2=Cummings |first2=O.R. |year=1997 |publisher=Boston Street Railway Association |isbn=0938315048 }}{{rp|39}} The extension ran from Scollay Square (where a new platform, Scollay Under, was constructed to replace Court Street station) to a new station and loop at Bowdoin Square. Tracks continued west under Cambridge Street to an incline at Joy Street, where streetcars could continue on surface tracks to Charles Street and the Longfellow Bridge to Cambridge.{{cite book |url=https://archive.org/stream/annualreportofbo21bost#page/44/mode/2up |pages=44–47 |title=Annual report of the Boston Transit Commission for the year ending June 30, 1915 |publisher=Boston Transit Commission |year=1915 |via=Internet Archive}}{{rp|31}}

Court Street station was abandoned on November 15, 1914, with service cut back to Devonshire.{{rp|39}} On March 13, 1916, service was extended to the new Scollay Under, with streetcars looping empty around the Bowdoin loop.{{cite news |url=https://www.newspapers.com/article/the-boston-globe/136818555/ |title=From Cambridge To East Boston |newspaper=The Boston Globe |date=March 12, 1916 |page=4 |via=Newspapers.com}} Bowdoin station opened on March 18 along with the Joy Street Portal, which was used by a Central Square–Orient Heights through line as well as several Cambridge lines that terminated at Scollay Under.{{cite news |url=https://www.newspapers.com/clip/53079017/the-boston-globe/ |title=Few Used New Bowdoin Sq Tunnel Immediately After its Opening |newspaper=Boston Globe |date=March 18, 1916 |page=14 |via=Newspapers.com}} {{open access}} The total cost of the extension was $2.4 million.

The East Boston Tunnel was originally planned to be operated with high-floor metro rolling stock and connected to the then-planned Cambridge Elevated line. When that plan was dropped in 1903 due to a disagreement between the Boston Transit Commission and the BERy, the stations were built with low platforms.{{cite book |title=Boston's Blue Line |last=Cheney |first=Frank |year=2003 |publisher=Arcadia Publishing |isbn=9780738535760}}{{rp|19}} Large bi-loading streetcars (with high floors but capable of loading from low platforms), which incorporated many attributes from metro cars used on the Main Line Elevated, began use in 1905.{{rp|118–119}}{{cite book |title=Surface cars of Boston, 1903-1963 |first1=Harold E. |last1=Cox |first2=O. R. |last2=Cummings |publisher=New England Electric Railway Historical Society |year=1963 |hdl = 2027/mdp.39015021059525}}{{rp|14}} However, neither these nor the large center-entrance cars introduced in 1917 (which were designed for multiple unit operation) could fully handle the crowds.{{rp|43}}

In 1921, the Boston Transit Department (BTD)—the successor to the BTC—began work at Maverick Square to convert the East Boston Tunnel to high-floor metro trains.{{cite book |url=https://books.google.com/books?id=kXl6J_T46psC&pg=PA30-IA7 |title=Annual Report of the Transit Department for the Year Ending January 31, 1922 |page=27 |publisher=Boston Transit Department |year=1922 |via=Google Books}} The next year, the BTD board approved the construction of high-level platforms at the four downtown stations.{{cite book |url=https://archive.org/details/annualreport1922trans/page/2 |title=Annual Report of the Transit Department for the Year Ending January 31, 1923 |page=3 |publisher=Boston Transit Department |year=1923 |via=Internet Archive}} The Maverick Square incline was replaced with Maverick station, which provided cross-platform transfers between tunnel trains and surface streetcars.{{rp|28}}

Over the weekend of April 18–21, 1924, the East Boston Tunnel was converted to use the new high-floor trains.{{cite book |title=Change at Park Street Under |last=Cudahy |first=Brian J. |year=1972 |publisher=Stephen Greene Press |isbn=0828901732 |lccn=72081531 |url-access=registration |url=https://archive.org/details/changeatparkstre00cuda/page/31 }} The tightly staged changeover required 1500 men to complete.{{rp|30}} Temporary wooden platform sections were put in place to allow service to begin on April 21, with the permanent concrete sections completed over the following months.{{cite book |url=https://babel.hathitrust.org/cgi/pt?id=uiug.30112107700418&view=1up&seq=279 |title=Annual Report of the Transit Department for the Year Ending January 31, 1925 |series=City document No. 33A |pages=35–36 |publisher=Boston Transit Department |year=1925 |via=HathiTrust}} The edges of the original low platforms can still be seen under the high platforms at State and Aquarium.{{cite news |url=http://archive.boston.com/news/local/massachusetts/articles/2011/05/29/among_the_new_renovations_blue_lines_past_appears_at_state_street/?page=full |title=Among the new renovations, Blue Line's past appears at State Street |newspaper=Boston Globe |date=May 29, 2011 |first=Eric |last=Moskowitz |access-date=March 29, 2020}} Rather than modify the narrow tunnel, the BERy elected to replace the streetcars with brand-new smaller-than-usual high-platform rapid transit cars which could operate in tight clearances—particularly around the tight loop at Bowdoin.{{rp|32}} Blue Line cars are thus {{convert|48.5|feet}} long, substantially shorter than the {{convert|65|feet|adj=on}} Orange Line cars and the {{convert|69.5|feet|adj=on}} Red Line cars.{{cite web|url=http://www.transithistory.org/roster/ |title=The MBTA Vehicle Inventory Page |publisher=NETransit |date=February 12, 2016 |access-date=February 12, 2016}}

File:Blue Line at Wonderland in 1967.jpg

From 1952 to 1954, a surface-level extension was constructed along the recently-defunct Boston, Revere Beach and Lynn Railroad, from Maverick to the current terminus at Wonderland. The original trackage had been narrow gauge, but was converted to standard gauge for this Revere Extension of the subway.{{rp|51}} The first above-ground station on the new extension served Boston's Logan Airport, and was the first American urban transit connection to a commercial airfield.{{rp|51}} Beyond Maverick, the power feed was changed from third rail to overhead catenary (both at 600 V DC) to reduce the risk of winter ice buildup due to proximity to the ocean.{{rp|51}}

The line was officially renamed the East Boston Tunnel & Revere Extension by the MTA in 1952, and designated as "Route 3" on system maps.{{cite map |title=System Route Map |date=1966 |title-link=:commons:File:1966 MBTA system map.png |publisher=Massachusetts Bay Transportation Authority |first=Richard F. |last=Lufkin |via=Wikimedia Commons}} It was renamed as the Blue Line on August 26, 1965, as part of the new MBTA's color-based rebranding. The color blue represented water, as the line passes under Boston Harbor and travels near the coast for much of its length.{{cite journal|last=Clarke|first=Bradley H.|title=The Boston Rapid Transit Album|journal=Boston Street Railway Association Bulletin|year=1981|issue= 17|page=13}} Until the Silver Line was extended to Logan in 2004–05, the Blue Line was the only rapid transit connection to the airport.

On April 21, 2018, the SL3 Silver Line service to Chelsea opened with a connection to the Blue Line at Airport station, providing transfer service to Chelsea, the Seaport District and South Station.

File:State station under construction.jpg

Unlike the Red Line and Orange Line, which had substantial new sections and station renovations in the 1970s and 1980s, most of the Blue Line had not been substantially modified since 1954. By the 1990 passage of the Americans with Disabilities Act, only {{bts|Suffolk Downs}} and the eastbound platform at {{bts|State}} were accessible, with {{bts|Wonderland}} then under construction.{{cite book |url=https://archive.org/stream/mbtaaccessguidet00mass#page/12/mode/2up |title=MBTA : ACCESS; The Guide to Accessible Services and Facilities |page=12 |date=June 1992 |publisher=Massachusetts Bay Transportation Authority |via=Internet Archive}}{{cite web |url=https://archive.org/details/ridershipservice990mass |edition=3 |title=Ridership and Service Statistics |date=November 1990 |pages=1–4 |publisher=Massachusetts Bay Transportation Authority |author=Operations Directorate Planning Division |via=Internet Archive}} In 1988, the MBTA began planning for accessibility modifications as well as platform extensions to accommodate 6-car trains - similar to what had been done on the Orange and Red lines. The project was then expected to be complete in 1994.{{cite news |url=https://www.newspapers.com/clip/38983306/the_boston_globe/ |title=MBTA renovation to enter blue period |date=July 4, 1988 |newspaper=Boston Globe |page=22 |first=Peter J. |last=Howe |via=Newspapers.com}} {{open access}} In 1989, the MBTA awarded design contracts for modernization and platform lengthening (to accommodate six-car trains) at nine Blue Line stations.{{cite book |url=http://web.mit.edu/cron/project/uncertainty/Dowd_Data/Baum_Snow/boston-history.txt |title=A Chronicle of the Boston Transit System |year=1992 |publisher=Massachusetts Bay Transportation Authority |via=Massachusetts Institute of Technology |last=Sanborn |first=George M. |access-date=February 21, 2016 |archive-date=November 27, 2019 |archive-url=https://web.archive.org/web/20191127202604/http://web.mit.edu/cron/project/uncertainty/Dowd_Data/Baum_Snow/boston-history.txt |url-status=dead }} Final design on a number of the modifications - the Blue Line Modernization Project - began in 1990–92.

The first main construction phase of the project began on June 25, 1994, the line was cut back to {{bts|Orient Heights}} at all times to permit reconstruction of the outer stations. {{bts|Beachmont}} and {{bts|Wood Island}} were completely rebuilt, while {{bts|Suffolk Downs}}, {{bts|Revere Beach}} and {{bts|Wonderland}} were renovated.{{cite news |url=https://www.newspapers.com/clip/39025579/the_boston_globe/ |title=MBTA to begin $467 million Blue Line project |newspaper=Boston Globe |date=March 20, 1994 |first=Andrew |last=Blake |via=Newspapers.com}} ([https://www.newspapers.com/clip/39025765/the_boston_globe/ second page]) {{open access}} A simultaneous $8 million noise reduction program added sound walls at Beachmont and Orient Heights, rubber mats under tracks, and soundproofing of nearby homes.{{cite news |url=https://www.newspapers.com/clip/39029165/the_boston_globe/ |title=T seeks quiet on Blue Line |newspaper=Boston Globe |date=October 26, 1994 |page=29 |via=Newspapers.com}} {{open access}} The stations reopened on June 26, 1995.{{NETransit}}{{cite news |url=https://www.newspapers.com/clip/39026158/the_boston_globe/ |title=Blue Line stations set to reopen after $467m upgrade |newspaper=Boston Globe |date=June 18, 1995 |first=Andrew |last=Blake |via=Newspapers.com}} ([https://www.newspapers.com/clip/39026284/the_boston_globe/ second page]) {{open access}} Unlike the other stations, Wood Island was not accessible after the 1994-95 renovation; elevators were not added until 2000.{{cite web |url=https://old.mbta.com/uploadedFiles/Accessibility/final%20report%20082407%20on%20CD.pdf |title=Evaluation of MBTA Paratransit and Accessible Fixed Route Transit Services: Final Report |publisher=Massachusetts Bay Transportation Authority |author=Tran Systems and Planners Collaborative |date=August 24, 2007}}{{cite web |url=http://www.mbta.com/text-only/schedmaps/map/map.pdf |title=Subway Map |date=2000 |publisher=Massachusetts Bay Transportation Authority |archive-url=https://web.archive.org/web/20000817174957/http://www.mbta.com/text-only/schedmaps/map/map.pdf |archive-date=August 17, 2000}}{{cite web |url=http://www.mbta.com/text-only/schedmaps/map/map.pdf |title=Subway Map |date=2001 |publisher=Massachusetts Bay Transportation Authority |archive-url=https://web.archive.org/web/20010701041753/http://www.mbta.com/text-only/schedmaps/map/map.pdf |archive-date=July 1, 2001}}

{{bts|Aquarium}} was closed from October 14, 2000, until October 29, 2001, for renovations, which were completed in 2003. A relocated {{bts|Airport}} station opened on June 3, 2004. An extensive renovation of {{bts|State}}, during which the station remained open, lasted from November 2004 to May 2011.{{cite press release |archive-url=https://web.archive.org/web/20041205145510/http://www.mbta.com/insidethet/press_releases_details.asp?ID=1069 |archive-date=December 5, 2004 |url=http://www.mbta.com/insidethet/press_releases_details.asp?ID=1069 |title=State Street Station Project To Begin |date=November 3, 2004 |publisher=Massachusetts Bay Transportation Authority}}{{cite press release |url=https://www.mbta.com/news/2011-05-26/patrick-murray-administration-highlights-mbta-blue-line-modernization-state-street |title=Patrick-Murray Administration Highlights MBTA Blue Line Modernization at State Street Station |date=May 26, 2011 |publisher=Massachusetts Bay Transportation Authority}} Sequential closures of Wonderland, Wood Island, Revere Beach, and Beachmont stations took place in June through November 2008 for platform repairs.{{cite press release |url=https://www.mbta.com/news/2008-06-18/blue-line-rehab-project-begin |title=Blue Line Rehab Project To Begin |date=June 18, 2008 |publisher=Massachusetts Bay Transportation Authority}}

Reconstruction of {{bts|Maverick}} began on October 4, 2005.{{cite press release |url=https://www.mbta.com/news/2005-10-04/construction-new-maverick-station-begins |title=Construction of New Maverick Station Begins |date=October 4, 2005 |publisher=Massachusetts Bay Transportation Authority}} The project was sufficiently progressed for six-car trains to enter service on September 15, 2008, though the station was not completed until 2009.{{cite report |title=Official Audit Report – Issued June 16, 2014: Massachusetts Bay Transportation Authority, For the period January 1, 2005 through December 31, 2012 |date=June 16, 2014 |url=https://www.mass.gov/files/documents/2016/08/ww/201305833a.pdf |publisher=Auditor of the Commonwealth |page=32}} Orient Heights was closed from March 23 to November 26, 2013, for a complete reconstruction. {{bts|Government Center}} closed from March 22, 2014, to March 21, 2016, for a complete renovation and accessibility modifications.{{cite news |url=https://www.bostonglobe.com/metro/2016/03/21/government-center-station-reopens/roZebAYCCykVGWPw7vVAeO/story.html |title=Government Center reopens |newspaper=Boston Globe |date=March 21, 2016 |first=Eric |last=Moskowitz |access-date=March 21, 2016}} This left all Blue Line stations accessible except for {{bts|Bowdoin}}, which also has an eastbound platform that cannot be modified for six-car trains.{{cite web |url=https://old.mbta.com/uploadedFiles/documents/2006_Annual_Report.pdf |title=DEP/EOT AMENDED ADMINISTRATIVE CONSENT ORDER AC0-BO-00-7001-AMENDMENT #2: 2006 Annual Report and 9th Status Report |date=June 30, 2006 |publisher=Massachusetts Department of Transportation |page=4}}

Service between Bowdoin and Airport was replaced by buses from May 18–31, 2020, and April 25 to May 17, 2022, for track replacement and waterproofing work in the East Boston Tunnel.{{cite press release |url=https://www.mbta.com/news/2020-05-08/building-better-t-14-day-blue-line-diversion-begins-may-18 |title=Building a Better T: 14-Day Blue Line Diversion Begins May 18 |date=May 8, 2020 |publisher=Massachusetts Bay Transportation Authority}}{{cite press release |url=https://www.mbta.com/news/2022-05-12/blue-line-suspension-between-airport-and-bowdoin-will-continue-through-tuesday-may |title=Blue Line Suspension between Airport and Bowdoin Will Continue through Tuesday, May 17

|date=May 12, 2022 |publisher=Massachusetts Bay Transportation Authority}} During the 2022 closure, temporary ferry service between Long Wharf and East Boston was also offered.{{cite press release |url=https://www.mbta.com/news/2022-04-11/upcoming-suspensions-blue-line-service-will-allow-crews-accelerate-infrastructure |title=Upcoming Suspensions of Blue Line Service Will Allow Crews to Accelerate Infrastructure Improvements |date=April 11, 2022 |publisher=Massachusetts Bay Transportation Authority}}{{cite press release |url=https://www.mbta.com/news/2022-05-08/blue-line-suspension-between-airport-and-bowdoin-extended-until-friday-may-13 |title=Blue Line Suspension between Airport and Bowdoin Extended Until Friday, May 13 |date=May 8, 2022 |publisher=Massachusetts Bay Transportation Authority}} An additional closure of the outer portion of the line from May 22 to June 8, 2022, allowed for repairs to the Suffolk Downs footbridge.{{cite press release |url=https://www.mbta.com/news/2022-05-18/upcoming-suspension-blue-line-train-service-between-wonderland-and-orient-heights |title=Upcoming Suspension of Blue Line Train Service between Wonderland and Orient Heights for 18 Days Begins Sunday, May 22 |date=May 18, 2022 |publisher=Massachusetts Bay Transportation Authority}} No fares were charged on the Blue Line from July 5 to August 31, 2023, during a closure of the Sumner Tunnel.{{cite news |last1=DeCosta-Klipa |first1=Nik |title=The entire MBTA Blue Line will be free during 2-month Sumner Tunnel closure this summer |url=https://www.wbur.org/news/2023/06/09/mbta-blue-line-free-sumner-tunnel-closure-cape-league-100-senate-tax-cuts-newsletter |newspaper=WBUR |access-date=June 10, 2023 |language=en |date=June 9, 2023}}{{cite press release |url=https://www.mass.gov/news/massachusetts-department-of-transportation-announces-alternative-travel-options-ahead-of-sumner-tunnel-closure |title=Massachusetts Department of Transportation Announces Alternative Travel Options Ahead of Sumner Tunnel Closure |date=June 9, 2023 |publisher=Massachusetts Department of Transportation}}

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{{anchor|Future plans}}

File:Lynn platform and parking garage.JPG, rebuilt in 1992, was designed to accommodate an extension of the Blue Line. The line would terminate between the commuter rail viaduct and the parking garage.]]

There is a proposal to extend the Blue Line northward to Lynn, Massachusetts. The land to extend the line was purchased for the initial construction of the Revere Extension, but due to budgetary constraints Wonderland station was designated the northern terminus. Two potential extension routes have been identified. One proposed path would run through marshland alongside the existing Newburyport/Rockport commuter rail line, on rail lines formerly operated by the Boston and Maine Railroad. An alternative route would extend the line alongside Revere Beach Boulevard through Point of Pines and the Lynnway, along the remainder of the BRB&L right of way.{{cite web |url=http://www.bostonmpo.org/bostonmpo/pmt-old/PMT-3.pdf |title=Chapter 5C System Expansion |archive-url=https://web.archive.org/web/20120206131017/http://www.bostonmpo.org/bostonmpo/pmt-old/PMT-3.pdf |archive-date=February 6, 2012 |access-date=October 14, 2007 |work=MBTA Program for Mass Transportation }} Other alternatives include increased commuter rail or bus service, or connecting the Blue Line to a commuter rail stop near Wonderland via a short connector.{{cite news| url=https://www.boston.com/news/local/articles/2007/12/13/plan_for_stretching_blue_line_to_lynn_gets_state_boost/?page=2 | work=The Boston Globe | title=Plan for stretching Blue Line to Lynn gets state boost | first=John | last=Laidler | date=December 13, 2007}}

The Blue Line extension has been proposed in various forms for over 80 years. The 1926 Report on Improved Transportation Facilities and 1945–47 Coolidge Commission Report recommended that the East Boston Tunnel line, which had been converted to rapid transit from streetcars in 1924, be extended to Lynn via the Boston, Revere Beach & Lynn right-of-way. Ever since the 1954 Revere extension was cut short to Wonderland, a further extension to Lynn has been planned. Following on the 1926 and 1945-47 studies, the 1966 Program for Mass Transportation recommended that the Blue Line be extended to Lynn, while the 1969 Recommended Highway and Transit Plan proposed that the extension run as far as Salem. An extension was not present in the 1972 Final Report of the Boston Transportation Planning Review, but the 1974 Transportation Plan revived the project with possible termini of Lynn, Salem, or even Route 128 in Peabody. The 1978 Program for Mass Transportation report and 1983 Transportation Plan both continued support for an extension to Lynn. Despite the continued recommendations, however, other projects like extensions of the Red and Orange lines were given funding instead of the Blue Line.

In 2005, Lieutenant Governor Kerry Healey estimated construction would begin in 2017.[http://www.lynndevelopment.com/dei_3_10_04.htm Blue Line Rolling into Lynn] by Thor Jourgensen. Lynn Office of Economic and Community Development. March 10, 2005. Authorization to bond for planning money for the project was included in an April 2008 state bond bill,{{Cite web |url=http://www.mass.gov/legis/laws/seslaw08/sl080086.htm |title=Chapter 86 of the Acts of 2008 |access-date=September 26, 2008 |archive-date=January 7, 2010 |archive-url=https://web.archive.org/web/20100107180149/http://www.mass.gov/legis/laws/seslaw08/sl080086.htm |url-status=dead }} and $25 million in federal earmarks have been obtained.{{cite news| url=https://www.boston.com/news/local/articles/2008/04/06/blue_line_blues/ | work=The Boston Globe | title=Blue Line blues | first=Steven | last=Rosenberg | date=April 6, 2008}} A 2004 state bond bill authorized $246.5 million on the condition of finding 50% non-state matching funds (which presumably would come from the federal government). The Draft Environmental Impact Report was expected to be complete by the end of 2008, but was delayed as planners focused on meeting the legal deadline for the Green Line extension to Somerville and Medford.{{cite web |last1=Jourgensen |first1=Thor |title=State spending mess, court ruling slows but doesn’t derail extension of Blue Line |url=https://itemlive.com/2009/02/05/state-spending-mess-court-ruling-slows-but-doesnt-derail-extension-of-blue-line/ |website=Itemlive |publisher=Itemlive |access-date=16 September 2024}}

{{Main|Red Line-Blue Line Connector}}

The Blue Line and Red Line are currently the only MBTA subway rail lines without a direct transfer to each other; passengers must ride one stop on the Green or Orange lines to transfer. The proposed Red–Blue connector would extend the Blue Line {{convert|0.4|miles}} west from Bowdoin to an underground platform at Charles/MGH station, allowing direct transfers to the Red Line.{{rp|1}}

File:Scheme 1 for Charles MGH station from 1986 study.png

An extension of the East Boston Tunnel to Charles Street was considered in a 1924 study of Charles station.{{cite news |url=https://www.newspapers.com/clip/57692766/the-boston-globe/ |title=Plans For New Tunnel Station |newspaper=Boston Globe |date=December 9, 1924 |page=1 |via=Newspapers.com}} {{open access}} A 1926 proposal to convert the Tremont Street subway and connecting streetcar lines into a pair of rapid transit trunk lines called for the East Boston Tunnel to be extended south to Park Street station, with through service running between Maverick Square and Brighton using the Commonwealth Avenue line. (Three potential alignment were considered: one running south from Bowdoin, and two running southwest from a relocated Scollay Under.) Regional transportation plans from the 1940s to the early 1970s focused on suburban extensions, with no downtown extension past Bowdoin.{{cite web |url=http://ntl.bts.gov/DOCS/boston.html |title=The Transportation Plan for the Boston Region - Volume 2 |date=November 15, 1993 |publisher=National Transportation Library |author=Central Transportation Planning Staff |archive-url=https://web.archive.org/web/20081021045641/http://ntl.bts.gov/DOCS/boston.html |archive-date=October 21, 2008}}

The rise of Kendall Square as a major employment center, the coming of the Red Line Northwest Extension, and increased traffic to Logan Airport created demand in the 1970s for a direct connection between the Red and Blue lines. A 1974 state plan again proposed an extension to Park Street, while the 1978 and 1983 Program for Mass Transportation updates called for an extension to Charles/MGH instead. A 1986 MBTA feasibility study for a Charles/MGH extension called for a cut-and-cover tunnel beginning west of Bowdoin Street with no changes to Bowdoin station. The project was then estimated to cost $79–95 million (equivalent to ${{inflation|US-GDP|79|1986}}–{{inflation|US-GDP|95|1986}} million in {{inflation-year|US-GDP}}).{{Inflation/fn|US-GDP}}{{cite book |archive-url=https://web.archive.org/web/20100816062620/http://www.eot.state.ma.us/redblue/downloads/1986/BOW-CHAR-CONN-PROJ-FULL.pdf |archive-date=August 16, 2010 |url=http://www.eot.state.ma.us/redblue/downloads/1986/BOW-CHAR-CONN-PROJ-FULL.pdf |title=Bowdoin Station and Charles Street Station Connector Project Feasibility Study |date=December 1986 |author=Seelye Stevenson Value & Knecht |publisher=Massachusetts Bay Transportation Authority}} A 1987 cost-effectiveness study estimated 9,030 daily one-way trips over the extension.{{cite book |archive-url=https://web.archive.org/web/20100816062625/http://www.eot.state.ma.us/redblue/downloads/1987/VOL-II-FULL.pdf |archive-date=August 16, 2010 |url=http://www.eot.state.ma.us/redblue/downloads/1987/VOL-II-FULL.pdf |page=PR-13 |title=Preliminary Ridership and Cost-Effectiveness Analyses Report |date=November 1987 |series=MBTA Bowdoin/Charles Connector Report: Preliminary Design and Environmental Studies Stats Report |volume=2 |author1=Howard Needles Tammen & Bergendoff |author2=Thomas K. Dyer Inc. |publisher=Massachusetts Bay Transportation Authority}}

In 1991, the state agreed to build a set of transit projects as part of the settlement of a lawsuit by the Conservation Law Foundation (CLF) over auto emissions from the Big Dig project. Among these projects was a Red Line–Blue Line connector, to be complete by the end of 2011.{{cite journal |url=https://www.federalregister.gov/citation/59-FR-50498 |journal=Federal Register |volume=59 FR 50498 |title=Approval and Promulgation of Air Quality Implementation Plans; Massachusetts—Amendment to Massachusetts' SIP (for Ozone and for Carbon Monoxide) for Transit Systems Improvements and High Occupancy Vehicle Facilities in the Metropolitan Boston Air Pollution Control District |author=United States Environmental Protection Agency |date=October 4, 1994}} The 2003–07 reconstruction of Charles/MGH station was designed to accommodate a future Blue Line platform.{{cite report |url=http://mbta.com/uploadedFiles/documents/CharlesMGH_design_summary_report.pdf |archive-url=https://web.archive.org/web/20100102122225/http://mbta.com/uploadedFiles/documents/CharlesMGH_design_summary_report.pdf |archive-date=January 2, 2010 |title=Charles/MGH Station Design Summary Report |date=August 31, 2000 |author=Elkus / Manfredi Architects Ltd – HDR |publisher=Massachusetts Bay Transportation Authority}} In 2005, the state replaced the connector with other projects providing equivalent air quality improvements. After a second lawsuit from the CLF, the state agreed in 2006 to complete design of the connector.{{cite news |archive-url=https://web.archive.org/web/20070228203257/http://www.boston.com/news/local/articles/2006/11/30/state_agrees_to_design_link_between_red_and_blue_lines/?page=full |archive-date=February 28, 2007 |url=https://www.boston.com/news/local/articles/2006/11/30/state_agrees_to_design_link_between_red_and_blue_lines/ |title=State agrees to design link between Red and Blue lines |newspaper=Boston Globe | date=November 30, 2006}}{{cite journal |url=https://www.federalregister.gov/documents/2008/07/31/E8-17595/approval-and-promulgation-of-air-quality-implementation-plans-massachusetts-amendment-to |title=Approval and Promulgation of Air Quality Implementation Plans; Massachusetts; Amendment to Massachusetts' State Implementation Plan for Transit System Improvements |date=July 31, 2008 |journal=Federal Register |volume=73 FR 44654 |author=United States Environmental Protection Agency}}{{cite web |archive-url=https://web.archive.org/web/20150710032301/http://www.massdot.state.ma.us/Portals/17/docs/sip/07sipAnnualRpt.pdf |archive-date=July 10, 2015 |url=http://www.massdot.state.ma.us/Portals/17/docs/sip/07sipAnnualRpt.pdf |title=State Implementation Plan – Transit Commitments: Status Report |date=July 2, 2007 |publisher=Executive Office of Transportation |pages=5–6}} An Expanded Environmental Notification Form was released in September 2007{{rp|1.1}}

File:Headhouse of Charles MGH station, December 2009.jpg

The 2010 Draft Environmental Impact Report (DEIR) instead called for a pair of deeper tunnels bored by a tunnel boring machine (TBM), starting east of Bowdoin station and passing underneath the existing platform. Keeping the existing station and loop was judged infeasible because evacuation from a disabled train would not be possible in the confined loop, and the eastbound platform is not long enough for six-car trains.{{rp|3–5}} Use of a TBM rather than cut-and-cover construction was intended to reduce construction cost and limit disruption on Cambridge Street.{{rp|3–7}} Alternatives with a replacement Bowdoin station west of Bowdoin Street, and without a replacement station, were considered; the latter was recommended due to lower cost and reduced travel time.{{cite book |url=http://www.eot.state.ma.us/redblue/downloads/DEIR/01_RBLC_DEIR_Text.pdf |archive-url=https://web.archive.org/web/20110108080441/http://www.eot.state.ma.us/redblue/downloads/DEIR/01_RBLC_DEIR_Text.pdf |archive-date=January 8, 2011 |title=RedLine/Blue Line Connector Project: Draft Environmental Impact Report |date=March 2010 |publisher=Massachusetts Department of Transportation}} The preferred alternative was estimated to cost $748 million and take six years to construct.{{rp|3–21}} Daily ridership was estimated to be 18,940 one-way trips in 2030.{{rp|3–21}}

Lacking available funding for construction, the MBTA did not complete design of the extension. The possibility of a public-private partnership (P3) to advance the project was studied in 2013.{{cite web |url=http://www.massdot.state.ma.us/Portals/0/docs/infoCenter/boards_committees/PublicPrivate/RedBlueConnector_P3ScreeningRpt.pdf |archive-url=https://web.archive.org/web/20170202012335/http://www.massdot.state.ma.us/Portals/0/docs/infoCenter/boards_committees/PublicPrivate/RedBlueConnector_P3ScreeningRpt.pdf |archive-date=February 2, 2017 |publisher=Massachusetts Department of Transportation |title=Red Line / Blue Line Connector P3 Project Suitability Assessment Report |date=September 11, 2013}} In 2015, the EPA removed the requirement for the MBTA to complete design.{{cite journal |url=https://www.federalregister.gov/documents/2015/12/08/2015-30819/approval-and-promulgation-of-air-quality-implementation-plans-massachusetts-transit-system |title=Approval and Promulgation of Air Quality Implementation Plans; Massachusetts; Transit System Improvements |journal=Federal Register |volume=80 FR 76225 |date=December 8, 2015 |author=United States Environmental Protection Agency}} In 2018, the state commissioned a $50,000 study to reevaluate tunneling costs; it found that contrary to the 2010 DEIR, cut-and-cover tunneling could be considerably less costly than a TBM, albeit with more surface disruption. Cut-and-cover was estimated to cost $200–250 million for the tunnel costs alone, compared to $300–350 million for TBM and the $413 million estimated in the DEIR.{{cite web |url=https://www.mass.gov/doc/summary-memorandum-tunnel-constructability/download |title=SUMMARY MEMORANDUM: TUNNEL CONSTRUCTABILITY STUDY: UPDATE TO THE 2010 DEIR FOR THE RED LINE/BLUE LINE CONNECTOR |date=October 2018 |publisher=Massachusetts Department of Transportation}}{{rp|28}} In 2019 and 2023, the MBTA indicated plans to spend $15 million to design the connector in a five-year spending plan.{{cite news |url=https://commonwealthmagazine.org/transportation/t-makes-quick-fix-on-red-blue-connector/ |title=T makes quick fix on Red-Blue connector |date=April 10, 2019 |first=Bruce |last=Mohl |newspaper=Commonwealth Magazine}}{{Cite news |last=Patkin |first=Abby |title=Here's where the MBTA's Red-Blue Connector stands |url=https://www.boston.com/news/local-news/2023/09/04/heres-where-the-mbtas-red-blue-connector-stands/ |access-date=September 17, 2023 |date=September 4, 2023 |newspaper=Boston Globe}}

A conceptual design completed in 2020 called for cut-and-cover construction, with Bowdoin station still planned for closure. The new Blue Line level at Charles/MGH would have entrances from the existing lobby and a new headhouse in an MGH development on the north side of Charles Street. Total project cost was estimated as $850 million ($740 million for construction including 30% contingency, $50 million for design, $30 million in administration costs, and $30 million for additional rolling stock), with construction lasting from 2025 to 2030.{{cite web |url=https://cdn.mbta.com/sites/default/files/2021-06/2021-06-07-fmcb-O-red-blue-connector-update.pdf |title=Red Blue Connector |date=June 7, 2021 |first=Erik |last=Stoothoff |publisher=Massachusetts Bay Transportation Authority}}{{cite book |url=https://cdn.mbta.com/sites/default/files/2021-12/2021-12-01-red-blue-concept-design-report.pdf |title=Red Blue Connector Concept Design Report |date=November 15, 2021 |publisher=Massachusetts Bay Transportation Authority}} A Notice of Project Change was issued on October 2, 2023.{{cite web |url=https://cdn.mbta.com/sites/default/files/2023-09/2023-10-02-red-blue-connector-notice-of-project-change.pdf |title=Notice of Project Change: Red Blue Connector Project |date=October 2, 2023 |publisher=Massachusetts Bay Transportation Authority}} In November 2023, the Massachusetts Executive Office of Energy and Environmental Affairs required the MBTA to prepare a Supplemental Draft Environmental Impact Report.{{cite web |url=https://eeaonline.eea.state.ma.us/EEA/MEPA-eMonitor/submittal/646cd449-ff5e-4b36-bee0-d88149e0727b |title=Certificate of the Secretary of Energy and Environmental Affairs on the Notice of Project Change |date=November 13, 2023 |first=Rebecca L. |last=Tepper |publisher=Massachusetts Executive Office of Energy and Environmental Affairs}}

A 2018 MBTA long-range planning document considered a pedestrian tunnel between the Orange Line platforms at {{bts|State}} and {{bts|Downtown Crossing}}, which would allow transfers between the Red and Blue lines similar to (though longer than) the Winter Street Concourse between the Green and Orange lines.{{cite news |url=https://commonwealthmagazine.org/transportation/t-urges-red-blue-pedestrian-link/ |title=T urges Red-Blue pedestrian link |first=Bruce |last=Mohl |date=June 18, 2018 |newspaper=Commonwealth Magazine}}

A physical rail connection between the Red and Blue Lines existed in the early part of the 20th century (prior to the MBTA assigning the color designations of the subway lines). Railcars from what is today the Blue Line could emerge from a ramp portal surfacing between Joy Street and Russell Street, just beyond Bowdoin station. The railcars would run on former streetcar track down Cambridge Street and then most of the distance to the western end of the Longfellow Bridge, connecting to what is now the Red Line just east of its Cambridge subway portal, near what is now Kendall/MIT station. Because the tracks were unpowered, individual cars had to be towed along the street at night. This connection was never used in passenger service, but was used to transport Blue Line cars to the Eliot Street Yard maintenance shops then located near Harvard Square station.{{rp|32}} When the Blue Line eventually got its own maintenance shops, the connection was removed and the ramp portal was permanently covered in 1952.{{rp|52}}{{cite web|title=Red Line Blue Line Connector (map)|url=http://www.eot.state.ma.us/redblue/downloads/map.pdf|publisher=Commonwealth of Massachusetts|access-date=July 28, 2011|archive-url=https://web.archive.org/web/20110928191724/http://www.eot.state.ma.us/redblue/downloads/map.pdf|archive-date=September 28, 2011}}

File:Suffolk Downs MBTA Blue Line Station, July 2023.jpg

File:Government Center MBTA Blue Line Platform, May 2024.jpg

File:MBTA Blue Line 0767 at State station, February 2023.jpg

Like the Orange Line and Red Line, the Blue Line tracks are standard-gauge heavy rail.{{cite web |url=http://world.nycsubway.org/us/boston/blue.html |title=MBTA Blue Line |access-date=October 14, 2007 |work=NYC Subway}} The Blue Line fleet comprises 94 700-series cars (47 pairs) with stainless steel bodies from Siemens, with each car {{convert|48|ft|m}} long and {{convert|9|ft|3|in|m}} wide, with two pairs of doors per side. Uniquely among MBTA rolling stock, Blue Line cars use both third rail power and pantograph current pickup from overhead catenary wires. The overhead pantograph was implemented to avoid third rail icing that frequently occurs in winter.{{rp|51}} Third rail power is used in the original Blue Line tunnels, which are smaller than most modern subway tunnels.{{rp|32}} Trains switch between the two modes at Airport station, near where the line transitions between running in a tunnel and running above ground. Previously, the switchover was made underground at Maverick station.{{rp|51}}

The MBTA awarded the $174 million construction contract for the 94 cars in November 2001, with a total program cost of $200 million. The first deliveries were scheduled for January 2004, but ultimately delayed to 2007 due to manufacturing issues.{{cite news |archive-url=https://web.archive.org/web/20061202054045/http://www.boston.com/news/local/articles/2006/11/29/t_slams_delays_in_blue_line_upgrade/ |archive-date=December 2, 2006 |first=Mac |last=Daniel |date=November 29, 2006 |title=T slams delays in Blue Line upgrade |newspaper=Boston Globe |url=https://www.boston.com/news/local/articles/2006/11/29/t_slams_delays_in_blue_line_upgrade/}} The first set entered revenue service on February 20, 2008.{{cite press release |url=https://www.mbta.com/news/2008-02-20/blue-line-gets-new-cars |title=Blue Line Gets New Cars |date=February 20, 2008 |publisher=Massachusetts Bay Transportation Authority}} The first three six-car trains began operating on September 15, 2008; by February 2009, eight of thirteen trainsets used at rush hour were six-car sets.{{cite press release |url=https://www.mbta.com/news/2008-09-15/six-car-trains-the-blue-line |title=Six-Car Trains on the Blue Line |date=September 15, 2008 |publisher=Massachusetts Bay Transportation Authority}}{{cite press release |url=https://www.mbta.com/news/2009-02-10/blue-line-capacity-keeps-growing |title=Blue Line Capacity Keeps Growing |date=February 10, 2009 |publisher=Massachusetts Bay Transportation Authority}} By November 2009, all service was with six-car trains.{{cite news |url=https://www.mbta.com/news/2009-11-19/blue-line-trains-attach-sixth-car |title=Blue Line Trains Attach Sixth Car |first=David |last=Liscio |newspaper=Lynn Daily Item |date=November 19, 2009 |via=MBTA}}

By February 2023, service was scheduled to operate at 5 to 5.5-minute headways at weekday peak hours and 9 to 11 minutes at other times. Peak service used 10–12 trains (60–72 cars), while other service used 5–6 trains (30–36 cars).{{cite magazine |magazine=Rollsign |publisher=Boston Street Railway Association |date=January–February 2023 |issue=1–2 |volume=60 |title=MBTA Vehicle Inventory as of February 28, 2023 |first=Jonathan |last=Belcher |page=3}} The MBTA expects to replace the current fleet in the mid-2030s after a 25-year operating lifespan. A 130-car fleet is planned to replace the existing 94-car fleet.{{cite web |url=https://cdn.mbta.com/sites/default/files/2021-01/2021-01-25-fmcb-M-blue-line-update.pdf |title=Blue Line Update |date=January 25, 2021 |first=Erik |last=Stoothoff |publisher=Massachusetts Bay Transportation Authority |page=5}}

The first generation of high-floor rolling stock on the line were the No. 1 and No. 2 East Boston Rapid Transit cars, which were built by Pullman-Standard in 1923–1924 when the line was converted from streetcar operation to rapid transit. These were supplemented by the No. 3 fleet, built in 1951 by St. Louis Car Company, which was acquired for the Revere Extension. Cars in these earlier fleets were numbered in the 0500 series.

The Nos. 1–3 fleets were replaced by 70 cars in the 0600 series (No. 4 cars), built 1978-1980 by Hawker Siddeley Canada Car and Foundry of Thunder Bay, Ontario, Canada. They were {{convert|48|ft|10|in|m}} long and {{convert|9|ft|3|in|m}} wide, with two pairs of doors on each side.{{cite book |url=https://old.mbta.com/uploadedFiles/documents/Bluebook%202007.pdf |title=Ridership and Service Statistics |publisher=Massachusetts Bay Transportation Authority |page=Ch02p07 |no-pp=yes |edition=11 |year=2007}} The design was based on the PA3 model used by PATH in New Jersey.{{citation needed|date=October 2019}} They were narrower and shorter than otherwise similar ones running on the Orange Line, due to the stations and tunnels on the Blue Line having been originally designed to accommodate streetcars.{{rp|32}}{{cite book |last=Clarke |first=Bradley |title=The Boston Rapid Transit Album |publisher=Boston Street Railway Association |year=1981 |location=Cambridge, Mass. |page=8}} In late 2009, the Seashore Trolley Museum received retired Hawker set 622-623 for their collection.{{cite web |url=http://www.trolleymuseum.org/documents/fundraiser-EastBoston4.pdf |title=We've saved a set of "bluebells" by acting quickly. Now we need your help to pay for the move |archive-url=https://web.archive.org/web/20120319192246/http://www.trolleymuseum.org/documents/fundraiser-EastBoston4.pdf |archive-date=March 19, 2012 |publisher=Seashore Trolley Museum}} By 2011, most of the 600-series cars were retired because of severe corrosion from the salty ocean air. Several 600-series cars were retained on MBTA property but no longer usable. Parts of scrapped cars are used to maintain Orange Line 1200 series rolling stock, which were built at the same time by Hawker Siddeley and used many of the same components.{{cite news |url=http://articles.boston.com/2012-07-08/metro/32575582_1_subway-cars-blue-line-cars-oldest-cars |archive-url=https://archive.today/20130119094948/http://articles.boston.com/2012-07-08/metro/32575582_1_subway-cars-blue-line-cars-oldest-cars |url-status=dead |archive-date=January 19, 2013 |title=MBTA mechanics keep old subway cars rolling |author=Moskowitz, Eric |newspaper=Boston Globe |date=July 8, 2012 |access-date=July 15, 2012 }} In 2012, set 616-617 was placed in the former Broadway streetcar tunnel for use in emergency training.{{cite news |url=http://www.bostonherald.com/news_opinion/local_coverage/2012/09/old_tunnel_turned_into_training_center_for_mbta |title=Old tunnel turned into training center for MBTA |date=September 18, 2012 |newspaper=Boston Herald |first=Christine |last=McConville}}

File:Blue Line at Wonderland in 1967.jpg|No. 1 cars at Wonderland in 1967

File:MBTA East Boston Tunnel Car interior in 1967.jpg|Interior of a No. 1 or No. 2 car

File:Train reversing at Wonderland, September 1965.jpg|No. 3 cars near Wonderland in 1965

File:Outbound train at Revere Beach station, July 2007.jpg|No. 4 cars at Revere Beach in 2007

{{reflist|30em}}

{{Commons category}}

{{Attached KML}}

• [https://mbta.com/schedules/Blue/line MBTA - Blue Line] (official site)
• [https://www.mbta.com/projects/red-blue-connector MBTA – Red Blue Connector]
• [https://web.archive.org/web/20130603161728/http://www.eot.state.ma.us/redblue/documents.htm Red-Blue Connector documents]
• [http://world.nycsubway.org/us/boston/blue.html Blue Line] at world.nycsubway.org

{{MBTA}}

{{USSubway}}

{{authority control}}

Category:Standard-gauge railways in the United States

Category:Tunnels completed in 1904

Category:Airport rail links in the United States

Category:600 V DC railway electrification

Category:Transportation in Suffolk County, Massachusetts