:Green Line Extension

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File:Inbound train on Red Bridge viaduct (1), March 2022.JPG

The GLX is primarily located in Somerville, northwest of downtown Boston, with its northernmost portion in Medford and its southernmost portion in the East Cambridge section of Cambridge. The GLX begins at the north end of the Lechmere Viaduct in East Cambridge, where a short elevated section formerly led to the surface-level Lechmere station at Lechmere Square. The new elevated GLX viaduct continues northwest for about {{convert|0.6|miles|1}}, paralleling the O'Brien Highway. A new elevated Lechmere station is located on the viaduct on the east side of Lechmere Square.{{rp|1{{hyphen}}2}} Two branches split at an aerial flying junction on the Red Bridge viaduct in the Inner Belt area.

The Medford Branch continues {{convert|3.0|mi|km|1}} northwest to {{bts|Medford/Tufts}}, with intermediate stations at {{bts|East Somerville}}, {{bts|Gilman Square}}, {{bts|Magoun Square}}, and {{bts|Ball Square}}. It runs in a below-grade cut along with the two-track Lowell Line and is operated as part of the E branch.{{rp|1{{hyphen}}2}} An extension of the Somerville Community Path runs along the west side of the Medford Branch south of Lowell Street, with a high bridge carrying it above the Red Bridge viaduct to a new terminus in the Northpoint development. An additional {{convert|0.9|mile|adj=on|1}} extension from Medford/Tufts to {{bts|Mystic Valley Parkway}} is proposed, but it is not being constructed as part of the main GLX.

The Union Square Branch continues {{convert|0.7|mi|km|1}} west to {{bts|Union Square|Green|D}}, with no intermediate stations. It runs at grade next to the two-track Fitchburg Line and is operated as part of the D branch.{{rp|1{{hyphen}}2}}

The vehicle maintenance facility (VMF) is located in the Inner Belt area adjacent to the MBTA Commuter Rail Maintenance Facility. It includes a four-track shop building, ten storage tracks with capacity for about 43 light rail vehicles (LRVs), a loop track, and a building for operator reporting and breaks. Yard leads connect the VMF to both branches near the Red Bridge flyover.{{rp|1{{hyphen}}6}}

The GLX is fully grade separated, with no road grade crossings, though there are level crossings for passengers at East Somerville and Ball Square stations.{{Cite web |date=December 2017 |title=Green Line Extension: Cambridge to Medford, Massachusetts |url=https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/funding/grant-programs/capital-investments/69846/ma-cambridge-medford-green-line-extension-fy19-profile.pdf |publisher=Federal Transit Administration}} Construction of the project included the replacement or modification of three rail bridges and seven road bridges.{{rp|8.3{{hyphen}}2}} Maximum speed on the extension is {{convert|50|mph}}, except for {{convert|10-20|mph}} limits for the Union Square Branch at Red Bridge.{{rp|1{{hyphen}}5}} As with the existing Green Line subway and D branch, the GLX has automatic block signaling with color light signals.{{rp|11.5{{hyphen}}1}} The signal system is designed for 5-minute headways on each branch, with 2{{frac|1|2}}-minute headways through Lechmere.{{rp|1{{hyphen}}4}}

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File:Ball Square station construction, July 2021.jpg

File:Aerial view of Lechmere station construction, September 2021.jpg

The seven GLX stations are accessible; all have elevators between street level and platform level except East Somerville, which has a ramp from street level. The stations have fare vending machines, but not faregates.{{rp|12.3{{hyphen}}1}} Most of the stations have island platforms {{convert|20-22.5|feet}} wide and {{convert|225|feet}} long – enough to fit three current LRVs or two future Type 10 LRVs – with provision to extend them to {{convert|300|feet}} in the future. The platform at Lechmere is {{convert|32-35|feet}} wide and {{convert|355|feet}} long – enough to fit two current two-car trains – as it would be difficult to later extend the elevated platform.{{Cite web |date=November 19, 2019 |title=Public meeting boards |url=https://www.mass.gov/doc/glx-pubilc-meeting-station-boards-november-19-2019/download |publisher=Massachusetts Bay Transportation Authority}}{{rp|12.1{{hyphen}}5}} The platforms are {{convert|8|in}} high for accessible boarding on current LRVs, and can be raised to {{convert|14|in}} for future level boarding with Type 9 and Type 10 LRVs.{{Cite web |date=December 11, 2017 |title=Execution Version: Volume 2: Technical Provisions |url=https://cdn.mbta.com/sites/default/files/projects/glx/contract/glx-technical-provisions.pdf |website=MBTA Contract No. E22CN07: Green Line Extension Design Build Project |publisher=Massachusetts Bay Transportation Authority}}{{rp|12.1{{hyphen}}5}}

Stations will have validators on the fare vending machines, with proof of payment enforcement in effect. When the station designs were simplified in 2016–17, faregates were removed from the plans. The MBTA expected AFC 2.0 (the Charliecard replacement system) to be fully in place by the time the GLX opened, with passengers able to board and tap their farecards at any door on trains. However, delays to the AFC 2.0 system means the GLX opened prior to all-door boarding being implemented.{{Cite news |last=Vaccaro |first=Adam |date=April 17, 2021 |title=The new Green Line will be ready in the fall. Paying for a ride, however, will be a little tricky. |work=Boston Globe |url=https://www.bostonglobe.com/2021/04/17/metro/new-green-line-will-be-ready-fall-paying-ride-however-will-be-little-tricky/ |access-date=April 17, 2021}}

File:Somerville Junction 1907 postcard.jpg

The Boston and Lowell Railroad (B&L) opened through South Medford, Somerville, and East Cambridge in 1835. Passenger service initially ran express between the two cities, but local stops were soon added.{{cite book |title=Steelways of New England |year=1946 |first=Alvin Fay |last=Harlow |publisher=Creative Age Press |pages=92–93}} The Charlestown Branch Railroad opened through Somerville and Charlestown in 1842; it was soon extended as the Fitchburg Railroad.{{Cite book |last1=Humphrey |first1=Thomas J. |title=Boston's Commuter Rail: The First 150 Years |last2=Clark |first2=Norton D. |publisher=Boston Street Railway Association |year=1985 |isbn=9780685412947}}{{rp|87}} In 1870, the B&L built a cutoff from {{bts|Lake Street|Lexington}} to Somerville Junction, which allowed Lexington Branch trains to enter Boston on the B&L.{{Cite magazine |date=February 4, 1871 |title=Boston and Lowell Railroad |url=https://books.google.com/books?id=0jkjAQAAMAAJ&pg=PA122 |magazine=American Railroad Journal |volume=27 |issue=5 |page=122 |via=Google Books}} The Massachusetts Central Railroad began service in 1881; it used most of the 1870-built cutoff to reach Boston.{{Cite book |last1=Humphrey |first1=Thomas J. |title=Boston's Commuter Rail: Second Section |last2=Clark |first2=Norton D. |publisher=Boston Street Railway Association |year=1986 |isbn=9780938315025 |page=12}}{{rp|216}} It was leased in 1886 by the B&L, which was in turn leased by the Boston and Maine Railroad (B&M) in 1887 as its Southern Division.{{rp|55}} The Fitchburg was leased by the B&M in 1900 as the Fitchburg Division.{{rp|88}} By the early 20th century, the Southern Division had stations at Medford Hillside and Tufts College in South Medford; North Somerville, Somerville Junction, Winter Hill, and Prospect Hill in Somerville; and East Cambridge. Stations were located on the Lexington Branch at North Cambridge, West Somerville, and Somerville Highlands. The Fitchburg Division had stations at Cambridge, Somerville, and Union Square.{{Cite book |last=Karr |first=Ronald Dale |title=The Rail Lines of Southern New England |publisher=Branch Line Press |year=2017 |isbn=9780942147124 |edition=2 |pages=247, 283}}{{rp|108}}

Horsecar service by the Cambridge Railroad in Somerville began in 1858 with lines from Union Square to Sullivan Square and to Elm Street (now Davis Square) via Somerville Avenue.{{Cite news |date=July 18, 1908 |title=This week in Cambridge fifty years ago |page=11 |work=Cambridge Chronicle |url=https://cambridge.dlconsulting.com/?a=d&d=Chronicle19080718-01.2.94&e=-------en-20--1--txt-txIN-------}}{{Humphrey Bus Report}}{{rp|205}} The Cambridge Railroad was granted permission in 1860 to run tracks over the Craigie Bridge from East Cambridge to Boston, joining with its existing line on Cambridge Street from Harvard Square, though service did not begin until around 1862.{{Cite news |date=August 3, 1860 |title=[Untitled] |page=4 |work=Boston Evening Transcript |url=https://www.newspapers.com/clip/82963346/boston-evening-transcript/ |via=Newspapers.com}}{{Cite magazine |last=Clarke |first=Bradley H. |date=May 2020 |title=Lechmere Station – The End of the End |magazine=Rollsign |publisher=Boston Street Railway Association |volume=57 |issue=5/6}}{{rp|14}} The Somerville Avenue line was extended from Union Square to Boston in 1864, joining the existing line at Lechmere Square in East Cambridge.{{rp|205}} The Cambridge Street line was converted to electric streetcar service by Cambridge Railroad successor West End Street Railway in 1891; the Somerville Avenue line and an 1888-built line to Davis Square via Highland Avenue were electrified and extended to Clarendon Hill in 1893–1895.{{rp|202, 205}}

The West End was leased to the Boston Elevated Railway (BERy) in 1897.{{Cite book |last1=Clarke |first1=Bradley H. |title=Tremont Street Subway: A Century of Public Service |last2=Cummings |first2=O.R. |publisher=Boston Street Railway Association |year=1997 |isbn=0938315048}}{{rp|35}} The three streetcar lines running through Lechmere Square began running into the Tremont Street subway upon its September 3, 1898, opening.{{rp|3}} Slow and unreliable service on the surface streetcar lines resulted in congestion in the subway.{{rp|5}} The Lechmere Viaduct and Causeway Street elevated opened on July 1, 1912, creating a grade-separated route from Lechmere Square to the subway and bypassing the Cragie Bridge.{{rp|4}} However, the surface lines through Somerville continued to be unreliable, and multiple-car trains were needed to increase subway capacity. On July 10, 1922, the BERy opened Lechmere station as a transfer point. Passengers on the Harvard Square and Clarendon Hill surface lines transferred to two-and-three-car subway trains, bringing rapid transit-style service to Lechmere.{{rp|5}}{{rp|44}}

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In 1907, the BERy proposed a branch of the Charlestown Elevated following Mystic Avenue from Sullivan Square to Medford Square.{{cite magazine |url=https://archive.org/details/electricrailwayr17amer/page/709 |page=709 |title=Rapid Transit in Boston and Vicinity |magazine=Electric Railway Journal |volume=17 |issue=22 |date=June 1, 1907}} In 1922, with the downtown subway network and several radial lines in service, the BERy indicated plans to build three additional radial subways: one paralleling the Midland Branch through Dorchester, a second branching from the Boylston Street subway to run under Huntington Avenue, and a third extending from Lechmere Square northwest through Somerville.{{Cite news |date=June 25, 1922 |title=Three New Subways Planned |page=71 |work=Boston Globe |url=https://www.newspapers.com/clip/52404512/the-boston-globe/ |via=Newspapers.com}} (The Dorchester line was eventually built as an extension of the Cambridge–Dorchester Tunnel later that decade, while a shorter Huntington Avenue subway opened in 1941.){{NETransit}}

The Report on Improved Transportation Facilities, published by the Boston Division of Metropolitan Planning in 1926, was the first comprehensive transit plan for the Boston area since the 1890s. The core recommendation of the report was a conversion of the Tremont Street subway to Maverick Square–Warren Street, Brighton and Lechmere Square–Brigham Circle, Roxbury rapid transit routes. Several suburban rapid transit extensions were proposed as secondary priorities; one would run in a dedicated median in the Northern Artery from Lechmere to Winter Hill, alongside the B&M Southern Division tracks to Somerville Junction, then follow the cutoff (by then called the Fitchburg Cutoff) to North Cambridge. Several branches of that line were listed as possible extensions: North Cambridge to {{bts|Bedford}} via the Lexington Branch, North Cambridge to {{bts|Waltham}} via the Fitchburg mainline, and Somerville Junction to {{bts|Woburn old}} via the Southern Division and Woburn Branch.{{Cite web |last=Central Transportation Planning Staff |date=November 15, 1993 |title=The Transportation Plan for the Boston Region - Volume 2 |url=http://ntl.bts.gov/DOCS/boston.html |url-status=dead |archive-url=https://web.archive.org/web/20010505072732/http://ntl.bts.gov/DOCS/boston.html |archive-date=May 5, 2001 |publisher=National Transportation Library}}{{Cite book |title=Report on Improved Transportation Facilities in Boston |date=December 1926 |publisher=Division of Metropolitan Planning |pages=6, 7, 34, 35 |hdl=2027/mdp.39015049422689}}

Variations on this plan were proposed several times during the 1930s. A 1935 proposal by a citizen's group called for a subway extension from {{bts|Haymarket}} or {{bts|Bowdoin}} surfacing in the North Station rail yards, then following the Southern Division and the Fitchburg Cutoff to Alewife Brook Parkway in North Cambridge. "High-speed trolley connections" would run to Arlington Heights and Belmont. A new expressway would have taken over the Causeway Street elevated and Lechmere Viaduct, then largely paralleled the new transit line to connect with the existing Mohawk Trail expressway at Alewife Brook Parkway.{{Cite news |date=February 27, 1935 |title=Rapid Transit Project Urged |page=28 |work=Boston Globe |url=https://www.newspapers.com/clip/50893896/the-boston-globe/ |via=Newspapers.com}} A 1938 proposal by Somerville mayor John M. Lynch called for an extension of the East Boston Tunnel from Bowdoin to the Lechmere Viaduct, a subway from Lechmere to Washington Street, and use of the Southern Division, Fitchburg Cutoff, and Lexington Branch to reach Arlington Center.{{Cite news |date=December 29, 1938 |title=Rapid Transit Line Proposed from Boston to Arlington |page=5 |work=Boston Globe |url=https://www.newspapers.com/clip/83380860/the-boston-globe/ |via=Newspapers.com}} A 1939 state resolve directed the Metropolitan District Commission to study that proposal.{{Cite book |title=Acts and resolves passed by the General Court in the year 1939 |publisher=Secretary of the Commonwealth |year=1939 |page=804 |chapter=Chapter 21: Resolve providing for an investigation by the Division of Metropolitan Planning relative to improving transportation facilities for the city of Somerville and the town of Arlington |chapter-url=https://archive.org/details/actsresolvespass1939mass/page/804/mode/2up |via=Internet Archive}}

File:1945 BERy extensions map.jpg

Transit service in Somerville declined during this period due to the Great Depression and competition from autos, many using the 1927-completed Northern Artery.{{Cite book |last=Clarke |first=Bradley H. |title=Streetcar Lines of the Hub - The 1940s |publisher=Boston Street Railway Association |year=2003 |isbn=0938315056}}{{rp|1}}{{Cite news |date=February 8, 1927 |title=New Two Way Streel Bridge at Auburn Place, Somerville, Completed and Open to Traffic |page=4 |work=Boston Globe |url=https://www.newspapers.com/clip/83534139/the-boston-globe/ |via=Newspapers.com}} East Cambridge, Prospect Hill, and the three Fitchburg Cutoff stations closed in 1927.{{Cite news |date=March 16, 1927 |title=Five B. & M. Stations Will Be Abandoned |work=Boston Daily Globe |url=https://www.newspapers.com/clip/36839725/the_boston_globe/ |via=Newspapers.com}} ([https://www.newspapers.com/clip/36839752/the_boston_globe/ second page]) {{open access}} Winter Hill closed in the 1930s, Union Square and Somerville in 1938, and Somerville Junction in the 1940s.{{Cite news |date=April 12, 1938 |title=At the State House |page=3 |work=Boston Globe |url=https://www.newspapers.com/clip/36820986/the_boston_globe/ |via=Newspapers.com}}{{open access}}{{Cite news |date=August 4, 1934 |title=Winter Hill station being razed - once pride of the B. & M. |page=10 |work=Boston Globe |url=https://www.newspapers.com/clip/36840810/the_boston_globe/ |via=Newspapers.com}}{{open access}} The Harvard Square–Lechmere route (now route {{MBTABus|69}}) was converted to trackless trolley in 1936.{{rp|202}} By 1940, six streetcar routes remained in Somerville: route {{MBTABus|87}} Clarendon Hill–Lechmere via Somerville Avenue, route {{MBTABus|88}}, Clarendon Hill–Lechmere via Highland Avenue, routes {{MBTABus|89}} Clarendon Hill–Sullivan Square and {{MBTABus|101}} Salem Street–Sullivan Square on Broadway, and two routes on the Fellsway running through East Somerville.{{rp|134}} Routes 87 and 88 were converted to trackless trolley in 1941; following heavy wartime ridership, routes 89 and 101 were converted in 1947.{{Cite news |date=November 6, 1941 |title='El' to Use Trackless Trolleys on Clarendon Hill-Lechmere Service |page=5 |work=Boston Globe |url=https://www.newspapers.com/clip/83535693/the-boston-globe/ |via=Newspapers.com}}{{rp|139}} Service on the Fellsway, which included Eastern Massachusetts Street Railway service to Stoneham until 1946, lasted until 1955.{{rp|148}}{{Cite book |last=Clarke |first=Bradley H. |title=Streetcar Lines of the Hub: Boston's MTA Through Riverside and Beyond |publisher=Boston Street Railway Association |year=2015 |isbn=9780938315070 |page=98}}

In 1943, the state legislature appointed a commission headed by Arthur W. Coolidge to plan for the future of transit in the Boston region. In 1945, a preliminary report from the Coolidge Commission recommended nine suburban rapid transit extensions – most similar to the 1926 plan – along existing railroad lines.{{rp|16}}{{Citation |last1=Boston Elevated Railway |title=Air View: Present Rapid Transit System – Boston Elevated Railway and Proposed Extensions of Rapid Transit into Suburban Boston |date=April 1945 |last2=Massachusetts Department of Public Utilities |title-link=:commons:File:1945 BERy extensions map.jpg |via=Wikimedia Commons}}{{Cite news |last=Lyons |first=Louis M. |date=April 29, 1945 |title=El on Railroad Lines Unified Transit Plan |pages=1, [https://www.newspapers.com/clip/83587536/the-boston-globe/ 14] |work=Boston Globe |url=https://www.newspapers.com/clip/83587444/the-boston-globe/ |via=Newspapers.com}} The proposed extension from Lechmere to Woburn followed the same alignment as the 1926 plan, albeit using an extended elevated structure rather than a subway north of Lechmere. A short subway segment was to be built to avoid the grade crossings at {{bts|Winchester Center}}.{{Cite book |last=Metropolitan Transit Recess Commission |url=https://archive.org/details/reportofmetropol00mass |title=Report of the Metropolitan Transit Recess Commission |date=April 1, 1947 |publisher=Commonwealth of Massachusetts |via=Internet Archive}} Annual ridership on the {{convert|9.18|miles|adj=on}} extension was estimated to be 11.8 million based on B&M and BERy ridership.{{Cite web |last=Metropolitan Transit Recess Commission |year=1945 |title=Proposed Rapid Transit Route: Lechmere to Woburn |url=http://www.somervillestep.org/background/GreenLine1945.html |archive-url=https://web.archive.org/web/20140222050857/http://www.somervillestep.org/background/GreenLine1945.html |archive-date=February 22, 2014 |website=Report of the Legislative Commission on Rapid Transit: 1945}} The 1947 final report modified some routes; the Woburn route was to be extended an additional {{convert|2|miles|0}} to North Woburn.{{Cite news |last=Casey |first=Gene R. |date=April 6, 1947 |title=10 Electric-Train Lines Proposed by Board in Report to Legislature |pages=1, 28 |work=The Boston Globe |url=https://www.newspapers.com/clip/42959374/the_boston_globe/ |via=Newspapers.com}} ([https://www.newspapers.com/clip/42959392/the_boston_globe/ second section], [https://www.newspapers.com/clip/42959409/the_boston_globe/ third page]) {{open access}}{{rp|18}} Cost was estimated at $3.627 million in 1941 dollars (equivalent to ${{inflation|US-GDP|3.627|1941}} million in {{inflation year|US-GDP}}).{{rp|13}} The Coolidge Commission also laid the groundwork for the 1947 transition of the BERy to public ownership as the Metropolitan Transit Authority (MTA).{{rp|17}}

In 1958, the B&M ended service to Medford Hillside, Tufts College, and North Somerville – the last three local stops south of {{bts|West Medford}} – due to declining ridership.{{Cite news |date=April 19, 1958 |title=Drastic Service Cuts Approved on Five B.& M. Divisions |page=11 |work=Daily Boston Globe |url=https://www.newspapers.com/clip/36829507/the_boston_globe/ |via=Newspapers.com}} {{open access}}{{Cite news |date=May 17, 1958 |title=B.&M. Closes Saugus Branch, 3 Other Lines |page=3 |work=Daily Boston Globe |url=https://www.newspapers.com/clip/36816192/the_boston_globe/ |via=Newspapers.com}}{{open access}} Route 101 was converted from trackless trolley to diesel bus in 1959; routes 69, {{MBTABus|80}} (not a former streetcar line), 87, 88, and 89 were all converted in 1963, leaving buses as the only remaining transit in Somerville and South Medford.{{Cite magazine |last=Barber |first=Richard |date=March–April 1984 |title=Pertinent Dates Relating to Trackless Trolley Operations |magazine=Rollsign |publisher=Boston Street Railway Association |volume=21 |issue=3/4 |page=15}} The 1962 North Terminal Area Study, claiming that the 1959 Highland branch conversion showed that PCC streetcars were inadequate for suburban rapid transit service, recommended that the elevated Lechmere–North Station segment be abandoned. The Main Line (now the Orange Line) was to be relocated along the B&M Western Route; it would have a branch to Woburn or Arlington via the Southern Division.{{Cite book |last=Barton-Aschman Associates |url=https://archive.org/details/northterminalare00bart |title=North Terminal Area Study |date=August 1962 |pages=51, 59–61 |via=Internet Archive}}

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The Massachusetts Bay Transportation Authority (MBTA) was formed in 1964 as an expansion of the MTA to subsidize suburban commuter rail service, as well as to construct rapid transit extensions to replace some commuter rail lines.{{rp|15}} In 1965, as part of systemwide rebranding, the Tremont Street subway and its connecting lines became the Green Line. The 1966 Program for Mass Transportation, the MBTA's first long-range plan, listed an approximately {{convert|1|mile|adj=on}} extension from Lechmere to Washington Street as an immediate priority. New Hampshire Division (Southern Division) passenger service would be cut back from North Station to a new terminal at Washington Street. A second phase of the project would extend Green Line service from Washington Street to Mystic Valley Parkway (Route 16) or West Medford.{{Cite book |url=https://archive.org/details/comprehensivedev00mass/page/n87/mode/2up |title=A Comprehensive Development Program for Public Transportation in the Massachusetts Bay Area |publisher=Massachusetts Bay Transportation Authority |year=1966 |pages=V-20 – V-23 |via=Internet Archive}}

The 1972 final report of the Boston Transportation Planning Review listed a Green Line extension from Lechmere to {{bts|Ball Square}} as a lower priority. The cost of the extension was estimated as $26 million (equivalent to ${{inflation|US-GDP|26|1966}} million in {{inflation year|US-GDP}}).{{Cite book |url=https://archive.org/details/bostontransporta00mass/mode/2up |title=Boston Transportation Planning Review Final Study Summary Report |date=February 1973 |publisher=Massachusetts Executive Office of Transportation and Construction |pages=15, 17 |via=Internet Archive}} Extension past Lechmere was listed as low priority in a 1974 plan due to the addition of Davis station to the planned Red Line Northwest Extension. (Davis opened in 1984 as the first MBTA subway station in Somerville.) An extension to Tufts University was listed as a proposal in the 1978 and 1983 updates to the Program for Mass Transportation.

In 1980, the MBTA began a study of the "Green Line Northwest Corridor" (from {{bts|Haymarket}} to Medford) with three area of focus: replacement of the Causeway Street elevated, replacement of Lechmere station, and extension beyond Lechmere.{{Cite journal |last=McCarthy |first=James D. |title=Boston's Light Rail Transit Prepares for the Next Hundred Years |url=http://onlinepubs.trb.org/Onlinepubs/sr/sr221/221-019.pdf |journal=Special Report 221: Light Rail Transit: New System Successes at Affordable Prices |publisher=Transportation Research Board |pages=286–308 |issn=0360-859X}}{{rp|293}} An evaluation report for the extension was published in 1981 and updated in 1984. Alternatives recommended for further evaluation included a Green Line extension to Tufts, a Green Line extension to {{bts|Union Square|Green|D}}, and a busway to Tufts and Davis.{{Cite web |date=June 3, 2004 |title=Beyond Lechmere Northwest Corridor Project Project History |url=https://www.somervillestep.org/files/GreenAdvisory_ProjectHistory_060304.pdf |publisher=Somerville Transportation Equity Partnership}}{{rp|308}} Later in the 1980s, the MBTA made plans to relocate Lechmere station as a precursor to an extension. A new elevated station would be located on the east side of the O'Brien Highway, with a new vehicle storage yard and maintenance facility to the north.{{rp|301}} The project was not pursued due to lack of available funding.{{Cite book |last=Vanasse Hangen Brustlin, Inc |url=https://web.archive.org/web/20160705134151/http://greenlineextension.eot.state.ma.us/docs_beyondLechmere.html |title=Beyond Lechmere Northwest Corridor Study: Major Investment Study/Alternatives Analysis |date=August 2005 |publisher=Massachusetts Bay Transportation Authority |page=2 |chapter=Introduction |chapter-url=http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter1.pdf |archiveurl=https://web.archive.org/web/20160705151118/http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter1.pdf |archivedate=July 5, 2016}} {{cbignore}}

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 Central Artery/Tunnel Project (Big Dig). Among these projects was a "Green Line Extension To Ball Square/Tufts University", to be complete by the end of 2011.{{Cite journal |last=United States Environmental Protection Agency |date=October 4, 1994 |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) |url=https://www.federalregister.gov/citation/59-FR-50498 |journal=Federal Register |volume=59 FR 50498}} While many of the projects were completed over the next 14 years, including the Old Colony Lines restoration and the South Boston Piers Transitway, the Green Line Extension was not advanced into planning. The 2003 Program for Mass Transportation considered both Green Line and Blue Line extensions to West Medford, including possible alignments through Union Square. Both modes were rated medium priority; the Blue Line version was twice as expensive due to the need to tunnel under the Charles River.{{cite book |url=https://www.ctps.org/data/pdf/studies/transit/PMT-2003.pdf |title=Program for Mass Transportation |pages=5C-33, 5C-37 |date=January 2004 |publisher=Central Transportation Planning Staff |chapter=Chapter 5C: System Expansion}} In March 2005, with the extension not in the MBTA's five-year plan, the city of Somerville and the CLF filed a lawsuit against the state for breaching the 1991 agreement.{{Cite news |last=Gedan |first=Benjamin |date=January 9, 2005 |title=City: T's been taking us for a Green Line ride |page=8 |work=Boston Globe City Weekly |url=https://www.newspapers.com/clip/83773843/the-boston-globe/ |via=Newspapers.com}}{{Cite news |date=March 15, 2005 |title=Suit aims to force spending on transit |page=18 |work=Boston Globe |url=https://www.newspapers.com/clip/83773982/the-boston-globe/ |via=Newspapers.com}}

In May 2005, the state announced an updated agreement, which revised the set of committed projects. Improvements to the Fairmount Line and increased Framingham/Worcester Line service were added; the Red-Blue Connector and Arborway service restoration were removed. The Green Line Extension was changed to include a branch to Union Square, with the main branch running to Medford Hillside. The project was estimated to cost $559 million (equivalent to ${{inflation|US-GDP|559|2005}} million in {{inflation year|US-GDP}}).{{Cite news |last=Daniel |first=Mac |date=May 19, 2005 |title=$770m transit plans announced |pages=B1, [https://www.newspapers.com/clip/83909659/the-boston-globe/ B4] |work=Boston Globe |url=https://www.newspapers.com/clip/83909630/the-boston-globe/ |via=Newspapers.com}} While the city of Medford was supportive of an extension as far as Medford Hillside, a potential further terminus at West Medford had less local support.{{Cite news |last=Daniel |first=Mac |date=May 13, 2005 |title=Medford, Somerville differ on T plan |work=The Boston Globe |url=http://archive.boston.com/news/local/articles/2005/05/13/medford_somerville_differ_on_t_plan/}}

The Beyond Lechmere Northwest Corridor Study, a Major Investment Study/alternatives analysis, was published in 2005. The analysis studied a variety of Green Line extensions (including a West Medford branch, a Union Square branch, both branches, and an extension to West Medford via Union Square and a tunnel under Prospect Hill), bus rapid transit (BRT) to West Medford and/or Union Square, commuter rail shuttles to West Medford or Anderson RTC with additional stops, and combinations of those modes.{{Cite book |last=Vanasse Hangen Brustlin, Inc |url=https://web.archive.org/web/20160705134151/http://greenlineextension.eot.state.ma.us/docs_beyondLechmere.html |title=Beyond Lechmere Northwest Corridor Study: Major Investment Study/Alternatives Analysis |date=August 2005 |publisher=Massachusetts Bay Transportation Authority |chapter=Chapter 4: Identification and Evaluation of Alternatives – Tier 1 |chapter-url=http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter4.pdf |archiveurl=https://web.archive.org/web/20160705151132/http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter4.pdf |archivedate=July 5, 2016}} {{cbignore}} The highest-rated alternatives were Green Line to West Medford (estimated cost $390 million), Green Line to both West Medford and Union Square ($438 million), and Green Line to Union Square plus BRT to West Medford ($340 million).{{Cite book |last=Vanasse Hangen Brustlin, Inc |url=https://web.archive.org/web/20160705134151/http://greenlineextension.eot.state.ma.us/docs_beyondLechmere.html |title=Beyond Lechmere Northwest Corridor Study: Major Investment Study/Alternatives Analysis |date=August 2005 |publisher=Massachusetts Bay Transportation Authority |chapter=Chapter 4: Identification and Evaluation of Alternatives – Tier 2 |chapter-url=http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter5.pdf |archiveurl=https://web.archive.org/web/20160705151143/http://greenlineextension.eot.state.ma.us/documents/beyondLechmere/MIS8-05-Chapter5.pdf |archivedate=July 5, 2016}} {{cbignore}}

The 2005 litigation was resolved by a November 2006 court settlement under which the Green Line Extension was to be completed in 2014.{{Cite news |last=Cummings |first=Claire |date=August 9, 2007 |title=Proponents rap delay to extend Green Line |work=The Boston Globe |url=http://archive.boston.com/news/local/articles/2007/08/09/proponents_rap_delay_to_extend_green_line/ |access-date=August 23, 2021}}{{Cite news |date=November 30, 2006 |title=State agrees to design link between Red and Blue lines |work=Boston Globe |url=https://www.boston.com/news/local/articles/2006/11/30/state_agrees_to_design_link_between_red_and_blue_lines/ |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}} This was approved by the Environmental Protection Agency in July 2008.{{Cite journal |last=United States Environmental Protection Agency |date=July 31, 2008 |title=Approval and Promulgation of Air Quality Implementation Plans; Massachusetts; Amendment to Massachusetts' State Implementation Plan for Transit System Improvements |url=https://www.federalregister.gov/documents/2008/07/31/E8-17595/approval-and-promulgation-of-air-quality-implementation-plans-massachusetts-amendment-to |journal=Federal Register |volume=73 FR 44654}} Proposed station sites were announced in May 2008: {{bts|Union Square|Green|D}}, {{bts|Brickbottom}}, {{bts|Gilman Square}}, {{bts|Lowell Street}}, {{bts|Ball Square}}, Medford Hillside (between College Avenue and Winthrop Street), and {{bts|Route 16}}.{{Cite news |last=Ryan |first=Andrew |date=May 7, 2008 |title=Potential Green Line stops announced in Somerville, Medford |work=The Boston Globe |url=https://www.boston.com/news/local/breaking_news/2008/05/potential_green.html |url-status=dead |archive-url=https://web.archive.org/web/20080510114546/http://www.boston.com/news/local/breaking_news/2008/05/potential_green.html |archive-date=May 10, 2008}}{{Cite web |last=Vanasse Hangen Brustlin, Inc |date=May 1, 2008 |title=Green Line Extension Project |url=http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/OverviewMap050508.pdf |publisher=Massachusetts Executive Office of Transportation and Public Works |archiveurl=https://web.archive.org/web/20160705150638/http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/OverviewMap050508.pdf |archivedate=July 5, 2016}}{{Cite web |last=Vanasse Hangen Brustlin, Inc |date=May 2, 2008 |title=Green Line Extension Project: Summary of Station Evaluations/Site Selections |url=http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/StationLocation050508.pdf |publisher=Massachusetts Executive Office of Transportation and Public Works |archiveurl=https://web.archive.org/web/20160705150637/http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/StationLocation050508.pdf |archivedate=July 5, 2016}} The former Yard 8 (located between the GLX tracks and Inner Belt Road) was chosen as the site for a maintenance and storage facility.{{Cite web |date=May 2, 2008 |title=Green Line Extension Project: Summary of Support Facility Evaluations/Site Selections |url=http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/SummarySuppFacility050508.pdf |publisher=Massachusetts Executive Office of Transportation and Public Works |archiveurl=https://web.archive.org/web/20160705150627/http://greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg6_050508/SummarySuppFacility050508.pdf |archivedate=July 5, 2016}} The project was widely supported in Somerville, where it was seen as a development catalyst and a correction for past transportation injustices, but was less popular in more suburban Medford.{{cite news |url=https://www.newspapers.com/clip/87438353/the-boston-globe/ |title=Rail plan offers change to get back on track |first= Eric |last=Moskowitz |newspaper=Boston Globe City Weekly |date=October 12, 2008 |pages=1, [https://www.newspapers.com/clip/87438749/the-boston-globe/ 10] |via=Newspapers.com}} Several potential tunnel alternatives – from Ball Square to {{bts|Alewife}}, an underground station at Union Square, and tunneling all or part of the Medford Branch – were analyzed in 2008 and found not to be cost-effective.{{cite book |archiveurl=https://web.archive.org/web/20170228145212/http://greenlineextension.eot.state.ma.us/documents/about/Topics/DraftDoc_TunnelAlts_112508.pdf |archivedate=February 28, 2017 |url=http://greenlineextension.eot.state.ma.us/documents/about/Topics/DraftDoc_TunnelAlts_112508.pdf |title=Consideration of Tunnel Alignment Alternatives |publisher=Massachusetts Executive Office of Transportation & Public Works |author=Vanasse Hangen Brustlin, Inc. |page=30}}

File:MysticValleyParkway MBTALowellLineBridge.jpg

The Massachusetts Executive Office of Transportation and Public Works submitted an Expanded Environmental Notification Form (EENF) to the Massachusetts Executive Office of Environmental Affairs in October 2006. The EENF identified a Green Line extension with Medford and Union Square branches as the preferred alternative, and sought permission to conduction a single environmental impact report.{{cite web |archive-url=https://web.archive.org/web/20160705151301/http://greenlineextension.eot.state.ma.us/documents/RelRegulatory/ExpandedENF.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/RelRegulatory/ExpandedENF.pdf |title=Green Line Extension Expanded Environmental Notification Form |date=October 2006 |publisher=Massachusetts Executive Office of Transportation and Public Works |author=TranSystems |pages=4–6}} That December, the Secretary of Environmental Affairs issued a certificate that instead required the preparation of separate draft (DEIR) and final (FEIR) environmental impact reports.{{cite web |archive-url=https://web.archive.org/web/20160705151236/http://greenlineextension.eot.state.ma.us/documents/RelRegulatory/SecretaryCertificate.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/RelRegulatory/SecretaryCertificate.pdf |date=December 1, 2006 |title=Certificate of the Secretary of Environmental Affairs on the Expanded Environmental Notification Form |first=Robert W. Jr. |last=Golledge |publisher=Massachusetts Executive Office of Environmental Affairs}} Work on the DEIR began in September 2007.{{cite web |archive-url=https://web.archive.org/web/20160705141002/http://greenlineextension.eot.state.ma.us/documents/PubMtgs/StaWrkshpsWinter2008/StaWrkshpsProjOverview.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/PubMtgs/StaWrkshpsWinter2008/StaWrkshpsProjOverview.pdf |title=Green Line Extension Project Station Workshops |page=5 |date=Winter 2008 |author=Massachusetts Executive Office of Transportation and Public Works}}

The DEIR was released in October 2009. West Medford was eliminated as a possible terminus due to the cost of modifying bridges over the Mystic River and Mystic Valley Parkway, as well as safety issues with two grade crossings.{{rp|2}} The proposed Medford Hillside station was replaced with College Avenue to improve access from the neighborhood to the north.{{rp|5}} The preferred alternative had branches to Route 16 and Union Square; however, due to cost constraints, the Route 16 terminus was deferred to a second phase, with the proposed alternative terminating at College Avenue.{{Cite book |url=https://web.archive.org/web/20160705134146/http://greenlineextension.eot.state.ma.us/docs_draftEIR.html |title=Green Line Extension Project Draft Environmental Impact Report / Environmental Assessment and Section 4(f) Statement |date=October 2009 |publisher=Massachusetts Executive Office of Transportation and Public Works; Federal Transit Administration |chapter=Chapter 3: Alternatives |chapter-url=http://greenlineextension.eot.state.ma.us/documents/draftEIR/Vol1Text/10_DEIR_EA_V1_CH3_Alts.pdf |archive-url=https://web.archive.org/web/20160705144443/http://greenlineextension.eot.state.ma.us/documents/draftEIR/Vol1Text/10_DEIR_EA_V1_CH3_Alts.pdf |archive-date=July 5, 2016}} {{cbignore}}{{rp|7}}

The FEIR was released in June 2010, with an estimated project cost of $845 million (equivalent to ${{inflation|US-GDP|845|2009}} million in {{inflation year|US-GDP}}). The primary change from the DEIR was the relocation of the maintenance facility about {{convert|1/4|mile}} to the east (adjacent to the MBTA Commuter Rail Maintenance Facility) due to local objections to the original site.{{Cite book |url=https://web.archive.org/web/20160705134140/http://greenlineextension.eot.state.ma.us/docs_finalEIR.html |title=Green Line Extension Project Final Environmental Impact Report |date=June 2010 |publisher=Massachusetts Executive Office of Transportation and Public Works; Federal Transit Administration |chapter=Executive Summary |chapter-url=http://greenlineextension.eot.state.ma.us/documents/FinalEIR/ExecutiveSummary.pdf |archive-url=https://web.archive.org/web/20160705141336/http://greenlineextension.eot.state.ma.us/documents/FinalEIR/ExecutiveSummary.pdf |archive-date=July 5, 2016}} {{cbignore}} In July 2010, the Massachusetts Department of Transportation (MassDOT) announced that the project was delayed to October 2015.{{cite news |url=https://www.newspapers.com/clip/87456626/the-boston-globe/ |title=Starts and Stops: Long-awaited Green Line extension to Somerville, Medford delayed again |newspaper=Boston Globe |first= Eric |last=Moskowitz |date=July 11, 2010 |page=B2 |via=Newspapers.com}}

In November 2010, the MBTA reached an agreement with Pan Am Railways and the NorthPoint developers under which the MBTA would receive property on the east side of O'Brien Highway needed for the new Lechmere station; in return, Pan Am would receive the existing Lechmere station site for redevelopment. The agreement, which also included MBTA trackage rights on the Worcester Branch and in New Hampshire, was amended in January 2011 and finalized that March.{{cite web |archiveurl=https://web.archive.org/web/20160705132622/http://greenlineextension.eot.state.ma.us/documents/about/Topics/AmendedLandXchgAgmt020711.pdf |archivedate=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/about/Topics/AmendedLandXchgAgmt020711.pdf |date=January 4, 2011 |title=Amended and Restated Development and Land Exchange Agreement |publisher=Massachusetts Department of Transportation}}{{cite press release |url=https://blog.mass.gov/transportation/mbta/mbta-new-lechmere-station-spurs-development/ |title=New Lechmere Station Spurs Development |date=March 3, 2011 |publisher=Massachusetts Department of Transportation |access-date=October 20, 2021 |archive-date=October 20, 2021 |archive-url=https://web.archive.org/web/20211020221551/https://blog.mass.gov/transportation/mbta/mbta-new-lechmere-station-spurs-development/ |url-status=dead }}

An additional delay, with service beginning between late 2018 and 2020, was announced in August 2011. This delay was due to difficulties with land acquisition – due to issues with the Greenbush Line reopening, the state decided to acquire all property before beginning construction – and concerns about cost controls and financing.{{cite news |url=https://www.newspapers.com/clip/87455079/the-boston-globe/ |title=Green Line extension put off until 2018 |first=Matt |last=Byrne |newspaper=Boston Globe |date=August 2, 2011 |page=B2 |via=Newspapers.com}} The delays beyond the legal deadline of December 31, 2014, created a requirement for MassDOT to implement interim projects to reduce emissions. The selected interim measures were increased midday frequency in the corridor (Green Line service to Lechmere plus bus routes {{MBTABus|80}}, {{MBTABus|88}}, {{MBTABus|91}}, {{MBTABus|94}}, and {{MBTABus|96}}), the purchase of hybrid vehicles for The Ride, and completion of new parking garages at {{bts|Salem}} and {{bts|Beverly}} stations.{{cite web |url=https://www.mass.gov/files/documents/2018/08/02/SIP18ComStatReport.pdf |title=State Implementation Plan – Transit Commitments: 2018 Status Report |pages=8, 9 |publisher=Massachusetts Department of Transportation |date=July 3, 2018}}

File:Press conference for Green Line Extension FFGA, January 5, 2015.jpg

In June 2012, the project was accepted into the preliminary engineering phase of the Federal Transit Administration (FTA) New Starts program – a requirement to access federal funding. By that time, the project was planned to cost $1.34 billion, including $200 million in finance charges.{{cite web |archiveurl=https://web.archive.org/web/20160705132547/http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/prelim_approval_letter061112.pdf |archivedate=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/prelim_approval_letter061112.pdf |date=June 11, 2012 |title=Re: Preliminary Engineering Approval for the Green Line Extension (GLX) Light Rail Transit Project |first=Mary Beth |last=Mello |publisher=Massachusetts Department of Transportation}} The project received a Finding of No Significant Impact (FONSI) from the FTA in July 2012.{{cite web |archive-url=https://web.archive.org/web/20160705141242/http://greenlineextension.eot.state.ma.us/documents/ev_Assess/fonsi_070912.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/ev_Assess/fonsi_070912.pdf |title=Finding of No Significant Impact |date=July 9, 2012 |publisher=Federal Transit Administration}} This allowed the MBTA to open bidding on the Phase 1 construction contract. The $13 million contract was awarded to Barletta Heavy Division that December.{{cite web |archive-url=https://web.archive.org/web/20150710031827/http://www.massdot.state.ma.us/Portals/17/docs/sip/2013%20SIP%20Annual%20Report%20-%20final.pdf |archive-date=July 10, 2015 |url=http://www.massdot.state.ma.us/Portals/17/docs/sip/2013%20SIP%20Annual%20Report%20-%20final.pdf |page=19 |date=July 1, 2013 |title=State Implementation Plan – Transit Commitments: 2013 Status Report |publisher=Massachusetts Department of Transportation}}{{cite web |url=https://bc.mbta.com/business_center/bidding_solicitations/awarded_contracts/?cnumber=E22CN01 |title=Harvard Street And Medford Street Railroad Bridge Reconstruction And 21 Water Street Demolition |date=2013 |publisher=Massachusetts Bay Transportation Authority |archive-url=https://web.archive.org/web/20211124015437/https://bc.mbta.com/business_center/bidding_solicitations/awarded_contracts/?cnumber=E22CN01 |archive-date=November 24, 2021}}{{rp|14}} Unlike later parts of the project, it used the traditional design–bid–build procurement method.{{cite book |url=https://marroninstitute.nyu.edu/uploads/content/Boston-Case_The-Story-of-the-Green-Line-Extension.pdf |title=The Boston Case: The Story of the Green Line Extension |publisher=NYU Marron Institute of Urban Management |first1=Eric |last1=Goldwyn |first2=Alon |last2=Levy |first3=Elif |last3=Ensari |date=December 9, 2020}}{{rp|14}}

The City of Somerville, MassDOT, and the MBTA reached an agreement in August 2012 to open the Union Square Branch by early 2017, with construction to begin in 2014.{{cite press release |url=https://www.somervillema.gov/news/city-massdot-mbta-sign-pact-green-line-station-development-union-square |title=City, MassDOT, MBTA Sign Pact on Green Line Station Development for Union Square |date=August 9, 2012 |publisher=City of Somerville}}{{cite news |url=https://www.newspapers.com/clip/87459487/the-boston-globe/ |title=Union Square site for T station |first=Matt |last=Byrne |newspaper=Boston Globe |date=August 9, 2012 |page=NO3 |via=Newspapers.com}} In September 2013, MassDOT awarded a $393 million (equivalent to ${{inflation|US-GDP|393|2013}} million in {{inflation year|US-GDP}}), 51-month contract for the construction of Phase 2/2A – Lechmere station, the Union Square Branch, and the first segment of the Medford Branch to Washington Street station – with the stations to open in early 2017.{{Cite news |last=Orchard |first=Chris |date=September 25, 2013 |title=$393 Million Approved to Bring Green Line to Union Square, Washington Street |work=Somerville Patch |url=http://somerville.patch.com/groups/politics-and-elections/p/393-million-approved-to-bring-green-line-to-union-square-washington-street |access-date=September 26, 2013}}{{Cite news |date=September 26, 2013 |title=State approves $393m for three new stations on Green Line |work=The Boston Globe |url=https://www.boston.com/yourtown/news/somerville/2013/09/state_approves_393m_for_three_new_stations_on_green_line.html |archive-url=https://web.archive.org/web/20130927021244/https://www.boston.com/yourtown/news/somerville/2013/09/state_approves_393m_for_three_new_stations_on_green_line.html |archive-date=September 27, 2013}} MassDOT intended to seek $557 million (equivalent to ${{inflation|US-GDP|557|2013}} million in {{inflation year|US-GDP}}) in federal funds for Phase 3 (construction of the maintenance facility) and Phase 4 (construction of the remainder of the Medford Branch), which were to be completed in 2019 or 2020.{{Cite news |last=Orchard |first=Chris |date=July 29, 2013 |title=Construction Firm Hired for Green Line Extension |work=Somerville Patch |url=http://somerville.patch.com/groups/business-news/p/construction-firm-hired-for-green-line-extension |access-date=July 29, 2013}}

In April 2014, governor Deval Patrick signed a $12.8 billion bonding bill, which included up to $1.3 billion (equivalent to ${{inflation|US-GDP|1.3|2014}} billion in {{inflation year|US-GDP}}) for the Green Line Extension.{{cite news |url=https://apnews.com/article/af1870278b6348509b26b38a0f2e4334 |title=Gov. Patrick signs transportation funding bill |date=April 18, 2014 |publisher=Associated Press}} Later that month, MassDOT announced that the $39 million Somerville Community Path extension would be included in the GLX project.{{cite press release |url=http://blog.mass.gov/transportation/mbta/green-line-extension-community-path-funding/ |title=Green Line Extension: Community Path Funding |date=April 30, 2014 |publisher=Massachusetts Department of Transportation |access-date=November 22, 2021 |archive-date=November 22, 2021 |archive-url=https://web.archive.org/web/20211122064521/http://blog.mass.gov/transportation/mbta/green-line-extension-community-path-funding/ |url-status=dead }} In May, MassDOT approved a $118 million contract with CAF USA to build 24 Type 9 LRVs to expand the Green Line fleet for GLX service.{{cite press release |url=https://www.mbta.com/news/2014-05-14/board-approves-purchase-new-green-line-cars-buses |title=Board Approves Purchase of New Green Line Cars and Buses |date=May 14, 2014 |publisher=Massachusetts Bay Transportation Authority}} In September 2014, the MBTA indicated that the cost would be $2.3 billion – $1.6 billion direct cost plus $400 million contingency and $300 million finance charges. This represented a $200 million increase in direct costs due to the addition of the Somerville Community Path extension, additional viaduct work near Lechmere, and additional construction management by design contractor AECOM/HNTB.{{cite news |url=https://www.boston.com/news/business/2015/08/28/the-long-depressing-history-of-green-line-extension-cost-increases/ |title=The long, depressing history of Green Line extension cost increases |newspaper=Boston Globe |first=Adam |last=Vaccaro |date=August 28, 2015}}{{cite news |url=https://www.wbur.org/news/2014/09/13/green-line-extension-cost-rises-to-2-billion |title=Green Line Extension Cost Rises To $2 Billion |newspaper=WBUR |date=September 13, 2014 |first=Andy |last=Metzger}} In December 2014, the FTA indicated that it would provide $996 million (equivalent to ${{inflation|US-GDP|0.996|2014|r=1}} billion in {{inflation year|US-GDP}}) of the $2.3 billion (equivalent to ${{inflation|US-GDP|2.3|2014|r=1}} billion in {{inflation year|US-GDP}}) total project cost, with the state funding the remaining portion.{{Cite news |last=Annear |first=Steve |date=December 2, 2014 |title=Government Will Pay for Nearly Half of the MBTA's Green Line Extension Project |work=Boston Magazine |url=http://www.bostonmagazine.com/news/blog/2014/12/02/mbta-green-line-extension-project-funding/ |access-date=October 28, 2021 |archive-date=January 25, 2022 |archive-url=https://web.archive.org/web/20220125072702/https://www.bostonmagazine.com/news/2014/12/02/mbta-green-line-extension-project-funding/ |url-status=dead }} The Full Funding Grant Agreement (FFGA) was signed in January 2015.

Internal cost estimates began to diverge even before funding was arranged. Construction costs were estimated at $1.17 billion by construction manager White Skanska Kiewit (WSK) in December 2013, with total project cost of $2.35 billion. However, a month later, project manager HDR/Gilbane produced estimates of $853 million and $1.83 billion. The MBTA budgeted $1.99 billion in June 2014 for total cost ($2.3 billion including finance charges), using the HDR/Gilbane estimate; this estimate was announced in September and used for the FFGA.{{cite news |url=https://www.boston.com/news/local-news/2016/01/15/report-green-line-extension-budget-issues-brewed-long-before-crisis/ |title=Report: Green Line extension budget issues brewed long before crisis |newspaper=Boston Globe |first=Adam |last=Vaccaro |date=January 15, 2016}}

In August 2015, the MBTA disclosed that projected costs had increased by $700 million–1 billion from the previous $1.99 billion figure.{{Cite web |last=Dungca |first=Nicole |date=August 24, 2015 |title=Green Line extension could cost another $1 billion |url=https://www.bostonglobe.com/metro/2015/08/24/mbta-green-line-extension-cost-billion-more-than-projected/dU65AoqBXDs4T33K97AMXN/story.html |publisher=The Boston Globe |archiveurl=https://web.archive.org/web/20160304092552/https://www.bostonglobe.com/metro/2015/08/24/mbta-green-line-extension-cost-billion-more-than-projected/dU65AoqBXDs4T33K97AMXN/story.html |archivedate=March 4, 2016}} Prices of several portions of the project had risen substantially, with Phase 2/2A rising from $387 million to $898 million.{{cite news |url=https://www.wbur.org/news/2015/08/24/ballooning-cost-green-line |title=Ballooning Cost Throws Future Of Green Line Extension Into Question |newspaper=WBUR |first=Andy |last=Metzger |date=August 24, 2015}} Critics including the CLF blamed the use of construction manager/general contractor (CM/GC) procurement process, under which WSK was able to set the cost of each subcontract, rather than a traditional process where the costs were set during bidding.{{cite news |archiveurl=https://web.archive.org/web/20151019045425/https://www.bostonglobe.com/metro/2015/09/14/contracting-process-cited-ballooning-costs-green-line-extension/2GIx45SiQdXotzJZJtmB5N/story.html |archivedate=October 19, 2015 |title=Process blamed for Green Line project's soaring cost |url=https://www.bostonglobe.com/metro/2015/09/14/contracting-process-cited-ballooning-costs-green-line-extension/2GIx45SiQdXotzJZJtmB5N/story.html |date=September 14, 2015 |first=Nicole |last=Dungca |newspaper=Boston Globe}} In December 2015, the MBTA ended its contracts with WSK and three other firms. Construction work in progress continued, but no new contracts were awarded.{{cite news |url=https://www.wbur.org/news/2015/12/10/green-line-extension-contracts |title=MBTA Ending Several Contracts Associated With Green Line Extension Project |newspaper=WBUR |date=December 10, 2015 |first=Abby Elizabeth |last=Conway}} At that time, cancellation of the project was considered possible, as were elimination of the Union Square Branch and other cost reduction measures.{{cite news |url=https://www.wbur.org/news/2015/12/09/green-line-extension-what-to-do |title=Axing Green Line Extension Still On The Table, Pollack Says |newspaper=WBUR |date=December 9, 2015 |first=Abby Elizabeth |last=Conway}}{{cite web |url=https://old.mbta.com/uploadedfiles/About_the_T/Board_Meetings/2015%2012%2009%20GLX%20VE%20MassDOT%20and%20FMC%20Boards%20ISSUE%20FINAL%20copy.pdf |title=Cost Reduction Opportunities |author=Arup |date=December 9, 2015 |publisher=Massachusetts Bay Transportation Agency}}

File:Longwood MBTA station, Brookline MA.jpg

In May 2016, the MassDOT and MBTA boards approved a modified project that had undergone value engineering to reduce its cost. Stations were simplified to resemble D branch surface stations rather than full rapid transit stations, with canopies, faregates, escalators, and some elevators removed. Two bridge replacements were avoided, and two others were reduced in scale by building a new span behind one abutment. The vehicle maintenance facility was reduced by half, with storage for 44 LRVs rather than 88. The southern section of the Community Path was removed – prompting criticism from trail advocates – and the number of street access points was reduced. These changes were projected to reduce total project cost back to the $2.3 billion established in the FFGA.{{cite book |title=Interim Project Management Team Report: Green Line Extension Project |url=https://old.mbta.com/uploadedfiles/About_the_T/Board_Meetings/GLXBOARDREPORTFINALv2.pdf |publisher=MBTA Fiscal and Management Control Board and the MassDOT Board of Directors |date=May 9, 2016 |pages=1–19}}{{Cite web |date=May 10, 2016 |title=State OK's a cut-down Green Line extension |url=https://www.newspapers.com/clip/89356496/the-boston-globe/ |first=Nicole |last=Dungca |newspaper=Boston Globe |pages=A1, [https://www.newspapers.com/clip/89356514/the-boston-globe/ A9] |via=Newspapers.com}}

That August, the FTA indicated it was "committed in principle" to the project but expressed reservations that any delays to the "optimistic" schedule could increase the project cost.{{cite news |url=https://www.bostonglobe.com/metro/2016/08/29/feds-make-reservations-clear-about-green-line-extension-but-encourage-moving-forward/wSL6e0aIeqGGpNJSWmjszO/story.html |archive-url=https://web.archive.org/web/20190119053326/https://www.bostonglobe.com/metro/2016/08/29/feds-make-reservations-clear-about-green-line-extension-but-encourage-moving-forward/wSL6e0aIeqGGpNJSWmjszO/story.html |archive-date=January 19, 2019 |title=Feds have reservations about Green Line, but encourage state to move forward |first=Nicole |last=Dungca |newspaper=Boston Globe |date=August 29, 2016}} A new project manager was hired in November 2016.{{cite news |url=https://www.bostonglobe.com/metro/2016/11/07/new-manager-named-lead-green-line-extension-project/jTVg6HytD4GPkSdkaTe2wI/story.html |archive-url=https://web.archive.org/web/20190827104217/https://www.bostonglobe.com/metro/2016/11/07/new-manager-named-lead-green-line-extension-project/jTVg6HytD4GPkSdkaTe2wI/story.html |archive-date=August 27, 2019 |title=New manager named to lead Green Line extension project |first=Nicole |last=Dungca |newspaper=Boston Globe |date=November 7, 2016}} In December 2016, the MBTA reached funding agreements under which Cambridge would contribute $25 million and Somerville $50 million. the MBTA announced a new planned opening date of 2021 for the extension.{{cite news |last=Dungca |first=Nicole |date=December 7, 2016 |title=New Green Line stations are delayed until 2021 |url=https://www.bostonglobe.com/metro/2016/12/07/new-green-line-stations-opening-delayed/S9Gc1c6PtbiSz7Wj3FVKkM/story.html |newspaper=Boston Globe |archive-url=https://web.archive.org/web/20161209145509/https://www.bostonglobe.com/metro/2016/12/07/new-green-line-stations-opening-delayed/S9Gc1c6PtbiSz7Wj3FVKkM/story.html |archive-date=December 9, 2016}} The FTA approved the revised cost estimate in April 2017.{{Cite news |last=Dungca |first=Nicole |date=April 4, 2017 |title=Green Line extension gets back on track |work=Boston Globe |url=https://www.newspapers.com/clip/89362518/the-boston-globe/ |pages=A1, [https://www.newspapers.com/clip/89362525/the-boston-globe/ A9]}} The first federal funds for the project were received in July 2017.{{Cite news |last=Vaccaro |first=Adam |date=July 17, 2017 |title=Federal officials fork over cash for Green Line extension |work=Boston Globe |url=https://www.bostonglobe.com/metro/2017/07/17/feds-fork-for-green-line-extension/flfSectIiSMt70fKkkadMP/story.html |archive-url=https://web.archive.org/web/20180810042331/https://www.bostonglobe.com/metro/2017/07/17/feds-fork-for-green-line-extension/flfSectIiSMt70fKkkadMP/story.html |archive-date=August 10, 2018}}

In February 2017, three consortia were shortlisted for the new design-build contract. The MBTA issued a final request for proposal to those three teams in May 2017. Proposals were required to be below an affordability limit of $1.319 billion in order to keep total project costs below $2.3 billion. Six additive options – elements removed during value engineering – were to be included if the teams could still meet cost and schedule requirements: station canopies, additional elevators at some stations, public art, an additional Community Path street connection, full-length extension of the Community Path, and improvements to the vehicle maintenance facility.{{cite press release |url=http://blog.mass.gov/transportation/mbta/mbta-green-line-extension-final-request-for-proposal-for-design-build-contract/ |title=MBTA Green Line Extension: Final Request for Proposal for Design-Build Contract |publisher=Massachusetts Department of Transportation |date=May 23, 2017 |access-date=November 23, 2021 |archive-date=November 23, 2021 |archive-url=https://web.archive.org/web/20211123012750/http://blog.mass.gov/transportation/mbta/mbta-green-line-extension-final-request-for-proposal-for-design-build-contract/ |url-status=dead }} In August 2017, construction manager CH2M was removed from the project to avoid a conflict of interest, as it was being acquired by Jacobs Engineering Group, which was also bidding on the construction contract.{{cite news |url=https://www3.bostonglobe.com/metro/2017/08/28/major-contractor-green-line-extension-removed-from-project/RYNbiHuNFYpxRHlhF4bjGL/story.html |archive-url=https://web.archive.org/web/20180312084111/https://www3.bostonglobe.com/metro/2017/08/28/major-contractor-green-line-extension-removed-from-project/RYNbiHuNFYpxRHlhF4bjGL/story.html |archive-date=March 12, 2018 |title=Major contractor on Green Line extension removed from project |newspaper=Boston Globe |first=Adam |last=Vaccaro |date=August 29, 2017}}

The three proposals were received in September 2017.{{rp|23}} Two of the three proposals were certified in October 2017 as meeting the affordability limit.{{cite press release |url=http://blog.mass.gov/transportation/mbta/mbta-green-line-extension-project-receiveds-affordability-limit-certifications-from-design-build-teams/ |title=MBTA Green Line Extension Project Receives Affordability Limit Certifications from Design Build Teams |publisher=Massachusetts Department of Transportation |date=October 23, 2017 |access-date=November 23, 2021 |archive-date=November 23, 2021 |archive-url=https://web.archive.org/web/20211123012748/http://blog.mass.gov/transportation/mbta/mbta-green-line-extension-project-receiveds-affordability-limit-certifications-from-design-build-teams/ |url-status=dead }} On November 17, 2017, the MBTA selected GLX Constructors (a consortium of Fluor Enterprises, the Middlesex Corporation, Herzog Contracting Corporation, and Balfour Beatty Infrastructure) to build the project. The consortium's base bid was $954 million, with all six additive options included; the $1.08 billion contract included contingency funds.{{Cite press release |title=Green Line Extension Project Design-Build Team Firm Selected |date=November 17, 2017 |publisher=Massachusetts Department of Transportation |url=http://blog.mass.gov/transportation/mbta/green-line-extension-project-design-build-team-firm-selected/ |last1=Jessen |first1=Klark |archive-url=https://web.archive.org/web/20220128223614/http://blog.mass.gov/transportation/mbta/green-line-extension-project-design-build-team-firm-selected/ |archive-date=January 28, 2022}}{{cite web |url=https://cdn.mbta.com/sites/default/files/fmcb-meeting-docs/2017/november/2017-11-20-fmcb-glx-update.pdf |title=GLX Program Update |date=November 20, 2017 |publisher=Massachusetts Bay Transportation Authority}}{{cite book |url=https://cdn.mbta.com/sites/default/files/projects/glx/contract/glx-technical-proposal-first-half.pdf |title=Response to the Request for Proposal for the Green Line Extension Design Build Project |publisher=GLX Constructors |date=September 2017}} ([https://cdn.mbta.com/sites/default/files/projects/glx/contract/glx-technical-proposal-second-half.pdf Volume 2]) The contract was awarded on November 20, 2017.{{cite news |url=https://www.bostonglobe.com/metro/2017/11/20/green-line-extension-contract-officially-approved/LpPWSUubsnzWbFtgTceDhI/story.html |archive-url=https://web.archive.org/web/20180124110730/https://www.bostonglobe.com/metro/2017/11/20/green-line-extension-contract-officially-approved/LpPWSUubsnzWbFtgTceDhI/story.html |archive-date=January 24, 2018 |title=Green Line extension contract officially approved |date=November 20, 2017 |newspaper=Boston Globe |first=Adam |last=Vaccaro}}

Several elements of the reduced-cost project design were criticized by community advocates and local politicians. E. Denise Simmons criticized the scaled-down station designs at Union Square and East Somerville for having long ramps rather than elevators, saying they were not sufficient for accessibility.{{cite news |url=https://www.cambridgeday.com/2019/03/19/anger-grows-over-design-of-green-line-stations-that-limit-access-and-add-distance-for-disabled/ |title=Anger grows over design of green line stations that limit access and add distance for disabled |first=Marc |last=Levy |date=March 19, 2019 |newspaper=Cambridge Day |archive-url=https://web.archive.org/web/20190325003510/https://www.cambridgeday.com/2019/03/19/anger-grows-over-design-of-green-line-stations-that-limit-access-and-add-distance-for-disabled/ |archive-date=March 25, 2019}} The Community Path extension is {{convert|10|feet}} wide, rather than the {{convert|11|feet|adj=on}} minimum in federal guidelines. The Friends of the Somerville Community Path criticized the path width, saying it would be a safety issue as cyclists in the same direction could not safely pass each other.{{Cite news |last=Vaccaro |first=Adam |date=May 13, 2019 |title=Somerville's getting a brand new bike path with the Green Line extension. Is it wide enough? |newspaper=The Boston Globe |url=https://www.bostonglobe.com/metro/2019/05/13/somerville-getting-brand-new-bike-path-with-green-line-extension-wide-enough/yN9ryYa2fDyZDWQGcO40PJ/story.html |archive-url=https://web.archive.org/web/20190514004737/https://www.bostonglobe.com/metro/2019/05/13/somerville-getting-brand-new-bike-path-with-green-line-extension-wide-enough/yN9ryYa2fDyZDWQGcO40PJ/story.html |archive-date=May 14, 2019}}

File:Proposed Mystic Valley Parkway station site (1), March 2022.JPG

The 1991 agreement to build the GLX specified "Ball Square/Tufts University" as the terminus; the 2005 update to the agreement substituted "Medford Hillside". By 2008, plans called for stations at Medford Hillside (between College Avenue and Winthrop Street) and Route 16/{{bts|Mystic Valley Parkway}}. However, the 2009 draft environmental impact report replaced the Medford Hillside station with one slightly to the south at College Avenue, and deferred Mystic Valley Parkway to a future second phase.{{rp|7}} During the comment periods for the 2010 final environmental impact report and the 2011 environmental assessment, some residents in Medford and Somerville questioned the advantages and legality of this change, claiming that College Avenue was not part of the Medford Hillside neighborhood and thus that the Mystic Valley Parkway station was needed to fulfill the commitment.{{cite web |url=http://greenlineextension.eot.state.ma.us/documents/FinalEIR/GLX_mtg20063010.pdf |archive-url=https://web.archive.org/web/20140222201618/http://greenlineextension.eot.state.ma.us/documents/FinalEIR/GLX_mtg20063010.pdf |archive-date=February 22, 2014 |title=Public Meeting – Summary Minutes |date=June 30, 2010 |publisher=Massachusetts Department of Transportation}} In January 2012, MassDOT stated that "the position of MassDOT and the MBTA on the configuration of the Green Line Extension is supported and has been reinforced by multiple regulatory agencies overseeing the [State Implementation Plan], including MassDEP."{{Cite web |last=Fichter |first=Katherine S. |date=January 10, 2012 |title=Responses to Comments on the October 2011 Environmental Assessment |url=http://greenlineextension.eot.state.ma.us/documents/ev_Assess/commentResponse011012.pdf |archive-url=https://web.archive.org/web/20140309111801/http://greenlineextension.eot.state.ma.us/documents/ev_Assess/commentResponse011012.pdf |archive-date=March 9, 2014 |page=6 |publisher=Massachusetts Department of Transportation}}

Construction of the Mystic Valley Parkway station was later planned from Boston MPO funds for 2016–2020 after the rest of the line was to be complete; however, this funding was reallocated to the main project after the cost overruns.{{cite news |url=https://patch.com/massachusetts/somerville/op-ed-build-green-line-extension-rt-16 |title=Op-Ed: Build The Green Line Extension To Rt. 16 |first=Christine |last=Barber |author-link=Christine Barber |date=November 10, 2017 |newspaper=Somerville Patch |access-date=November 28, 2021}} Some environmental review for the extension has taken place, with a notice of project change released in October 2017.{{cite book |url=https://www.mass.gov/doc/notice-of-project-change-0/download |title=Notice of Project Change: Green Line Extension to Mystic Valley Parkway |date=October 2017 |publisher=Massachusetts Department of Transportation}}

An extension of the Union Square Branch to {{bts|Porter}} has also been proposed by local officials.{{cite news |url=https://www.cambridgeday.com/2022/03/01/lechmere-union-square-t-stops-open-march-21-as-council-reminds-of-porter-square-connection/ |title=Lechmere, Union Square T stops open March 21 as council reminds of Porter Square connection |first=Marc |last=Levy |date=March 1, 2022 |newspaper=Cambridge Day |access-date=March 2, 2022}} Union Square station is designed so as to not preclude such an extension.{{cite web |url=https://www.mass.gov/doc/union-square-branch-glx-roll-plan-4/download |title=Union Square Branch – GLX Roll Plan 4 |date=November 2019 |publisher=Massachusetts Bay Transportation Authority}}{{cite web |url=https://www.mass.gov/doc/glx-community-working-group-november-5-2019-meeting-minutes/download |title=November 5, 2019 Community Working Group Meeting – Summary Minutes |date=November 5, 2019 |page=1 |publisher=Massachusetts Department of Transportation}}

Phase 1 consisted of the reconstruction of two railroad bridges (over Harvard Street in Medford and over Medford Street in Somerville) for Green Line tracks, and the demolition of a disused MBTA facility at 21 Water Street in Cambridge to make room for the new Lechmere station.{{cite web |archive-url=https://web.archive.org/web/20160705135443/http://greenlineextension.eot.state.ma.us/documents/PubMtgs/Phase1/Phase1_presentation_030513.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/PubMtgs/Phase1/Phase1_presentation_030513.pdf |title=Green Line Extension Phase 1 Early Bridge & Demolition Public Meeting |date=March 5, 2013 |publisher=Massachusetts Department of Transportation}} Construction began with a groundbreaking ceremony held at the Medford Street bridge on December 11, 2012.{{Cite press release |date=December 11, 2012 |title=Green Line Extension Phase 1 Construction Begins |url=http://blog.mass.gov/transportation/mbta/green-line-extension-phase-1-construction-begins/ |publisher=Massachusetts Department of Transportation |access-date=November 24, 2021 |archive-date=November 24, 2021 |archive-url=https://web.archive.org/web/20211124062841/http://blog.mass.gov/transportation/mbta/green-line-extension-phase-1-construction-begins/ |url-status=dead }}{{Cite news |last=Rosenberg |first=Steven A. |date=December 5, 2013 |title=Somerville poised to grow along Green Line |work=The Boston Globe |url=https://www.bostonglobe.com/metro/regionals/north/2013/12/05/somerville-poised-grow-along-green-line/OnY8VW8fhT8aVZqKcw4X2K/story.html |archive-url=https://web.archive.org/web/20180816015053/https://www.bostonglobe.com/metro/regionals/north/2013/12/05/somerville-poised-grow-along-green-line/OnY8VW8fhT8aVZqKcw4X2K/story.html |archive-date=August 16, 2018}} Notice to proceed was issued to Barletta Heavy Division on January 31, 2013, and construction started in March.{{Cite news |date=March 20, 2013 |title=MBTA gets set to lay tracks |work=The Somerville News |url=http://www.thesomervillenews.com/archives/36388 |archive-url=https://web.archive.org/web/20130324024945/http://www.thesomervillenews.com/archives/36388 |archive-date=March 24, 2013}} The 21 Water Street facility was demolished in August 2014.{{Cite web |last=MassDOT |date=August 25, 2014 |title=2014_08_25 MBTA Building at 21 Water St in Cambridge Demolition_2 |url=https://www.flickr.com/photos/massdot/15034565052/in/set-72157633388240699/ |publisher=Massachusetts Department of Transportation |via=Flickr}} Originally planned to last until early 2015, Phase 1 work was completed in October 2015.{{cite web |archive-url=https://web.archive.org/web/20160331224527/http://www.massdot.state.ma.us/Portals/17/docs/sip/2015_SIP_Annual_Report_Final.pdf |archive-date=March 31, 2016 |url=http://www.massdot.state.ma.us/Portals/17/docs/sip/2015_SIP_Annual_Report_Final.pdf |title=State Implementation Plan – Transit Commitments: 2015 Status Report |page=16 |date=August 28, 2015 |publisher=Massachusetts Department of Transportation}}

Notice to proceed with the Type 9 LRV contract was given to CAF in September 2014.{{cite web |url=https://old.mbta.com/uploadedfiles/About_the_T/Board_Meetings/E.%20MBTA%20Type%209%20Board%20Update%20Mar%2020%202017%20Rev%2010%20w-notes-video.pdf |title=Green Line Type 9 Project Update |page=2 |date=March 27, 2017 |publisher=Massachusetts Bay Transportation Authority}} The first LRV was delivered in March 2018 and entered service that December.{{cite news |url=https://www3.bostonglobe.com/metro/2018/03/24/first-new-green-line-cars-has-arrived/CmzKpY7No7qxV0sdgDJ06I/story.html |archive-url=https://web.archive.org/web/20180328213012/https://www3.bostonglobe.com/metro/2018/03/24/first-new-green-line-cars-has-arrived/CmzKpY7No7qxV0sdgDJ06I/story.html |archive-date=March 28, 2018 |title=First of 24 new Green Line cars has arrived |first=Adam |last=Vaccaro |date=March 24, 2018 |newspaper=Boston Globe}}{{Cite press release |title=New MBTA Green Line Car goes into Passenger Service |date=December 21, 2018 |publisher=Massachusetts Bay Transportation Authority |url=https://www.mbta.com/news/2018-12-21/new-mbta-green-line-car-goes-passenger-service}} The remaining 23 LRVs were delivered in 2018–2020 and entered service in 2019–2021.{{cite magazine |magazine=Rollsign |publisher=Boston Street Railway Association |title=MBTA Vehicle Inventory as of February 28, 2021 |pages=8, 9 |first=Jonathan |last=Belcher |date=January–February 2021 |volume=58 |issue=1/2}}

File:GLX Phase 1.svg|alt=A map of the GLX corridor with the Medford Street bridge, Harvard Street bridge, and 21 Water Street circled|Map of Phase 1 construction locations

File:Somerville mayor Curtatone at GLX groundbreaking.JPG|alt=Joseph Curtatone speaking at a podium|Somerville mayor Joseph Curtatone at the 2012 groundbreaking ceremony

File:Green Line Extension 2014 08 21 MBTA Building at 21 Water St in Cambridge Demolition Progress 1 - Copy (14855773018).jpg|alt=A cinderblock building being demolished by an excavator|Demolition of the 21 Water Street facility in August 2014

File:Laying new spans on the Harvard Street bridge, July 2015.JPG|alt=A crane lifting a steel beam onto a bridge|Harvard Street bridge work in July 2015

File:Type 9 on first day of revenue service, December 2018.jpg|alt=A modern light rail vehicle at an underground station|Type 9 LRV on its first day of service in 2018

{{quotebox|quote=I swore publicly that I would never come to another groundbreaking of the Green Line because I had already been to three. Today is different because this one is real. It’s been a long time coming.|author=Mike Capuano, US Representative and former Somerville mayor, on the 2018 groundbreaking|width=300px}}

Some construction work on the main project, including piers for the Red Bridge viaduct, took place in 2014–15 before the project was put on hold.{{cite web |archive-url=https://web.archive.org/web/20160705143010/http://greenlineextension.eot.state.ma.us/documents/wrkGroup/febMtg2015/presentation022315.pdf |archive-date=July 5, 2016 |url=http://greenlineextension.eot.state.ma.us/documents/wrkGroup/febMtg2015/presentation022315.pdf |title=GLX Working Group Presentation |date=February 23, 2015 |publisher=Massachusetts Department of Transportation}} The FTA released the first $100 million in funding in December 2017, allowing the MBTA to issue a notice to proceed for the main construction contract.{{cite press release |url=https://www.mbta.com/news/2017-12-21/federal-funds-issued-mbta-green-line-extension-project |title=Federal Funds Issued for MBTA Green Line Extension Project |date=December 21, 2017 |publisher=Massachusetts Bay Transportation Authority}} Some work like tree clearing, removal of old siding tracks, and geotechnical boring took place in the first half of 2018, while design of stations and other complex elements continued.{{cite web |url=https://www.mass.gov/doc/march-8-2018-0/download |title=GLX Project-Wide Public Meeting |date=March 7, 2018 |publisher=Massachusetts Department of Transportation}}{{cite web |url=https://www.mass.gov/doc/july-18-2018/download |title=GLX General Public Meeting |date=July 18, 2018 |publisher=Massachusetts Department of Transportation}} A groundbreaking ceremony was held on June 25, 2018.{{cite news |url=https://www.wbur.org/news/2018/06/25/green-line-extension-groundbreaking |title=Officials Break Ground On Green Line Extension |newspaper=WBUR |date=June 25, 2018 |access-date=November 24, 2021}} Viaduct construction, drainage work, and retaining wall and noise wall erection began in the second half of 2018.{{cite web |url=https://cdn.mbta.com/sites/default/files/fmcb-meeting-docs/2019/01-january/2019-01-14-fmcb-glx-update-original.pdf |title=Green Line Extension Update |date=January 14, 2019 |publisher=Massachusetts Department of Transportation}} Temporary relocation of the Lowell Line tracks, which allowed for the construction of retaining walls to widen the cut to accommodate the GLX tracks, was completed in October 2018. By the end of 2018, station designs were 60% complete.{{cite web |pages=14, 26 |url=https://www.mass.gov/doc/january-30-2019-glx-public-meeting-presentation/download |title=GLX Project Open House |date=January 30, 2019 |publisher=Massachusetts Department of Transportation}}

The Homans Building, a former food distribution facility adjacent to the Gilman Square station site, was demolished in April 2019.{{cite press release |url=https://www.mbta.com/projects/green-line-extension-glx/update/homans-building-demolition |title=Homans Building Demolition |date=April 19, 2019 |publisher=Massachusetts Bay Transportation Authority}} The pace of construction increased in mid-2019, with annual spending increasing from $170 million to $400 million.{{cite news |url=https://www.bostonglobe.com/metro/2019/04/21/slowly-but-surely-green-line-extension-coming-along/pVGdQ6TsSMmdU8p91zvBmL/story.html |archive-url=https://web.archive.org/web/20190423131635/https://www.bostonglobe.com/metro/2019/04/21/slowly-but-surely-green-line-extension-coming-along/pVGdQ6TsSMmdU8p91zvBmL/story.html |archive-date=April 23, 2019 |date=April 21, 2019 |first=Adam |last=Vaccaro |title=Making tracks: Pace of work on Green Line extension project is picking up |newspaper=Boston Globe}} Four station designs reached 100% completion in October 2020, with the remaining three nearly complete. Construction reached 20% completion in November 2019.{{Cite news |last=Thompson |first=Katie |date=November 15, 2019 |title=Construction on Green Line extension 20 percent complete |work=WCVB |url=https://www.wcvb.com/article/construction-on-green-line-extension-20-percent-complete/29811265 |archive-url=https://web.archive.org/web/20210624202351/https://www.wcvb.com/article/construction-on-green-line-extension-20-percent-complete/29811265 |archive-date=June 24, 2021}} Viaduct spans were being installed by that time, and the commuter rail tracks were shifted to the east side of the cut (allowing construction on the Green Line tracks and stations to proceed) late in 2019.{{cite web |url=https://www.mass.gov/doc/glx-public-meeting-presentation-november-19-2019/download |title=GLX Project Public Meeting |date=November 19, 2019 |publisher=Massachusetts Department of Transportation}}

The project required the temporary closure of three road bridges (Broadway, School Street, and Medford Street) and one underpass (Washington Street) for bridge reconstruction. All but School Street closed between March and May 2019; School Street closed in April 2020, with Washington Street and Broadway reopening that May and June.{{cite web |url=https://www.mass.gov/doc/bridge-closures-fall-2021/download |title=GLX Bridge Closure Matrix |date=August 17, 2021 |publisher=Massachusetts Department of Transportation}} Medford Street reopened in July 2022 and School Street in December 2022.{{cite web |url=https://www.mass.gov/doc/bridge-closures-fall-2022/download |title=Bridge Closures |date=November 1, 2022 |publisher=Massachusetts Department of Transportation}}{{cite press release |url=https://www.somervillema.gov/news/school-street-bridge-reopens-saturday-december-10 |title=School Street Bridge Reopens Saturday, December 10 |date=December 8, 2022 |publisher=City of Somerville}} Green Line service was cut back from Lechmere to North Station effective May 24, 2020, to permit connection of the Lechmere Viaduct to the new GLX viaduct.{{cite press release |url=https://mbta.com/news/2020-04-15/glx-update-mbta-announced-dedicated-bus-lanes-slated-charles-river-dam-road |title=GLX Update: MBTA Announced Dedicated Bus Lanes Slated for Charles River Dam Road |date=April 15, 2020 |publisher=Massachusetts Bay Transportation Authority}} (The work was originally expected to require closing the viaduct for 17 months – the third major disruption of Lechmere service since 2004 – causing opposition to the closure in Cambridge.{{Cite news |last=Levy |first=Marc |date=February 26, 2014 |title=Second 17-month T disruption looms for Lechmere; public market idea still alive |work=Cambridge Day |url=http://www.cambridgeday.com/2014/02/26/second-17-month-service-disruption-looms-for-lechmere-public-market-idea-still-alive/ |access-date=May 2, 2014}} In November 2019, plans were revised to reduce this to 11 months,{{Cite news |last=Levy |first=Marc |date=November 20, 2019 |title=Buses will be back for 11 months at Lechmere as green line extension T project rolls onward |work=Cambridge Day |url=https://www.cambridgeday.com/2019/11/20/buses-will-be-back-for-11-months-at-lechmere-as-green-line-extension-t-project-rolls-onward/}} although the viaduct remained closed until the start of service to Union Square in 2022, a period of 22 months.) Demolition of the old northern section of the Lechmere Viaduct began on June 6, 2020.{{Cite press release |title=GLX to Begin Demolishing Section of Lechmere Viaduct This Weekend |date=June 5, 2020 |publisher=Massachusetts Bay Transportation Authority |url=https://www.mbta.com/news/2020-06-05/glx-begin-demolishing-section-lechmere-viaduct-weekend}} The main section of the viaduct was rehabilitated during the closure under a separate project.{{cite web |url=https://cdn.mbta.com/sites/default/files/2019-12/2019-12-09-fmcb-K-lechmere-viaduct-project-accessible.pdf |title=Repair/Rehabilitation of East Cambridge (Lechmere) Viaduct |first=Karl E. |last=Eckstrom |date=December 9, 2019 |publisher=Massachusetts Bay Transportation Authority}}

The project was over 50% completed by October 2020.{{Cite press release |title=Baker-Polito Administration, Transportation Officials Visit Green Line Extension Project |date=October 1, 2020 |publisher=Massachusetts Bay Transportation Authority |url=https://www.mbta.com/news/2020-10-01/baker-polito-administration-transportation-officials-visit-green-line-extension}} Most station platform work took place in the second half of 2020; by the end of the year, steel canopies and other structures were under construction at several stations.{{cite web |url=https://www.mass.gov/doc/glx-virtual-public-meeting-presentation-december-9-2020/download |title=GLX General Public Meeting |date=December 9, 2020 |publisher=Massachusetts Department of Transportation}} The final concrete span of the Red Bridge viaduct was poured in December 2020, with ballast laid later that month and track laying starting in January 2021.{{cite web |url=https://www.mass.gov/doc/glx-virtual-public-meeting-presentation-january-5-2021/download |pages=18, 19 |title=GLX Community Working Group Monthly Meeting #38 |date=January 5, 2021 |publisher=Massachusetts Department of Transportation}} By March 2021, the Union Square Branch was expected to open in October 2021, followed by the Medford Branch in December 2021.{{Cite web |date=March 29, 2021 |title=Report from the General Manager |url=https://cdn.mbta.com/sites/default/files/2021-03/2021-03-29-fmcb-9-report-from-general-manager.pdf |publisher=Massachusetts Bay Transportation Authority |page=20}} By the beginning of June 2021, 65% of track was in place, as were 8 of 9 signal houses.{{Cite web |last=Wagner |first=Jeff |date=June 1, 2021 |title=GLXC Construction Update |url=https://www.mass.gov/doc/glx-virtual-cwg-meeting-presentation-june-1-2021/download |publisher=Massachusetts Bay Transportation Authority}}

In June 2021, the MBTA indicated an additional delay, due in part to effects from the COVID-19 pandemic, under which the Union Square Branch was planned to open in December 2021, followed by the Medford Branch in May 2022.{{Cite web |last=Dalton |first=John |date=June 21, 2021 |title=Green Line Extension Update |url=https://cdn.mbta.com/sites/default/files/2021-06/2021-06-21-fmcb-14-green-line-extension-update.pdf |page=19 |publisher=Massachusetts Bay Transportation Authority}}{{Cite news |last=Lisinski |first=Chris |date=June 22, 2021 |title=Green Line extension to Medford delayed five months |publisher=Boston Globe |url=https://www.bostonglobe.com/2021/06/22/metro/green-line-extension-medford-delayed-five-months/ |archive-url=https://web.archive.org/web/20210624204228/https://www.bostonglobe.com/2021/06/22/metro/green-line-extension-medford-delayed-five-months/ |archive-date=June 24, 2021}} The first test train was moved to the new VMF in August 2021 to begin testing of the Union Square Branch. Medford Branch testing was then expected to begin in late 2021 or early 2022. The Community Path extension will open along with the Medford Branch, as it is used for construction access.{{Cite news |last=MilNeil |first=Christian |date=August 3, 2021 |title=Green Line Extension Update: Trains Arrive in Somerville |work=Streetsblog Mass |url=https://mass.streetsblog.org/2021/08/03/green-line-extension-update-trains-arrive-in-somerville/}} The D branch was extended to North Station on October 24, 2021, with the B and C branches moved to Government Center, as part of changes in preparation for the opening of the extension.{{cite web |archiveurl=https://web.archive.org/web/20211014192326/https://www.mbta.com/alerts/subway |archivedate=October 14, 2021 |title=Alerts: Subway |url=https://www.mbta.com/alerts/subway |date=October 14, 2021 |publisher=Massachusetts Bay Transportation Authority}}{{cite news |url=https://www.boston.com/news/local-news/2021/10/22/green-line-terminal-station-changes-glx-testing/ |title=A 'subtle' but permanent change is coming to the Green Line this weekend |first=Nik |last=DeCosta-Klipa |date=October 22, 2021 |newspaper=Boston Globe |accessdate=October 24, 2021}} In October 2021, the Union Square Branch opening was delayed to March 2022 due to delays with a substation at Red Bridge, with the Medford Branch opening likely delayed past May 2022.{{cite news |url=https://www.boston.com/news/local-news/2021/10/21/green-line-extension-union-square-branch-delay-march/ |title=The opening of the first Green Line Extension branch has been delayed — again |newspaper=Boston Globe |date=October 21, 2021 |first=Nik |last=DeCosta-Klipa}} Train testing on the Union Square Branch began in December 2021.{{cite press release |url=https://www.mbta.com/projects/green-line-extension-glx/update/test-trains-now-running-the-green-line-extension |title=Test Trains Now Running on the Green Line Extension |date=December 23, 2021 |publisher=Massachusetts Bay Transportation Authority}}

The project reached 85% completion in November 2021. That month, MassDOT moved to return the contributions from Cambridge and Somerville, as the combination of construction being under budget and American Rescue Plan Act funds being received meant the municipal monies were not needed.{{cite web |url=https://cdn.mbta.com/sites/default/files/2021-11/11-17-2021-5-and-6-green-line-extension.pdf |title=GLX Municipal Contributions |date=November 17, 2021 |publisher=Massachusetts Department of Transportation}} Medford Branch testing began in May 2022 following the March 2022 opening of the Union Square Branch.{{cite press release |url=https://www.mbta.com/projects/green-line-extension-glx/update/train-testing-begins-new-green-line-medford-branch |title=Train Testing Begins on New Green Line Medford Branch |date=July 5, 2022 |publisher=Massachusetts Bay Transportation Authority}} Total project cost is estimated to be $2.28 billion: $0.996 billion from the federal government and $1.28 billion from state and other sources. Daily ridership on the extension is projected to be 45,000 by 2030.{{Cite web |title=About the Green Line Extension Project |url=https://www.mass.gov/info-details/about-the-green-line-extension-project |access-date=November 27, 2021 |publisher=Massachusetts Department of Transportation}}

File:Brush clearing for Medford Branch construction, April 2018.jpg|alt=Brush being fed into a wood chipper next to a railway line|Brush clearing on the Medford Branch in April 2018

File:Broadway bridge demolition (1), March 2019.jpg|alt=A bridge being demolished by four excavators|Broadway bridge under reconstruction in March 2019

File:Homan Building demolition, April 2019.webm|alt=A video of a large brick building being demolished by a wrecking ball|Demolition of the Homans Building in April 2019

File:Iron worker on Red Bridge viaduct, September 2019.jpg|alt=A worker atop a partially complete bridge|An ironworker on the Red Bridge viaduct in September 2019

File:Steel frame erection at GLX Vehicle Maintenance Facility, May 2020.jpg|alt=A metal frame for a large building|The frame of the vehicle maintenance facility in May 2020

File:Aerial view of Lechmere station construction, May 2020.png|alt=An overhead view of a partially built elevated railway station|The new Lechmere station under construction in May 2020

File:Dust control for Lechmere Elevated demolition, June 2020.jpg|alt=Water being sprayed onto an excavator demolishing an elevated railway viaduct|Demolition of the northern section of the Lechmere Viaduct in June 2020

File:Union Square station platform construction (2), November 2020.JPG|alt=A railway station platform with the frame of a metal canopy|Union Square station with canopy frame in November 2020

File:Somerville Community Path ramp to Cross Street under construction, July 2021.jpg|alt=A concrete ramp under construction next to a railway line|Ramp for the Somerville Community Path in July 2021

File:Magoun Square station under construction (2), December 2021.JPG|alt=A light rail station under construction in an open cut|Magoun Square station nearing completion in December 2021

File:MBTA 3849 at Union Square station, March 2022.jpg

Plans prior to construction called for the Union Square Branch to be through-routed with the E Branch and the Medford Branch to be through-routed with the D Branch.{{Cite web |date=January 6, 2011 |title=MBTA Light Rail Transit System OPERATIONS AND MAINTENANCE PLAN |url=http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/NewStartsSubmittal_FY2012/Attachments/Attachment_10P_OMP_010611.pdf |archive-url=https://web.archive.org/web/20170307152841/http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/NewStartsSubmittal_FY2012/Attachments/Attachment_10P_OMP_010611.pdf |archive-date=March 7, 2017 |publisher=Massachusetts Bay Transportation Authority}}{{Cite web |date=January 2012 |title=Travel Forecasts: Systemwide Stats and SUMMIT Results |url=http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/NewStartsSubmittal_FY2012/Attachments/Attachment_3_Combined.pdf |archive-url=https://web.archive.org/web/20170307152239/http://greenlineextension.eot.state.ma.us/documents/FTA_NewStarts/NewStartsSubmittal_FY2012/Attachments/Attachment_3_Combined.pdf |archive-date=March 7, 2017 |website=Green Line Extension Project: FY 2012 New Starts Submittal |publisher=Massachusetts Department of Transportation}} However, in April 2021, the MBTA indicated that these would be reversed, with the D going to Union Square and the E to Medford/Tufts.{{Cite news |last=DeCosta-Klipa |first=Nik |date=April 9, 2021 |title=The MBTA is planning to open part of the Green Line Extension this October |work=Boston Globe |url=https://www.boston.com/news/local-news/2021/04/09/mbta-green-line-extension-union-square-october |access-date=April 9, 2021}} The D and E branches were chosen for the extension because they serve the Longwood Medical Area; the D branch was assigned to the shorter Union Square Branch because its western leg is longer than that of the E branch. The Union Square Branch was initially served by the E branch rather than the D branch.{{cite web |archive-url=https://web.archive.org/web/20211130001042/https://www.mbta.com/projects/green-line-extension-glx |archive-date=November 30, 2021 |url=https://www.mbta.com/projects/green-line-extension-glx |title=Green Line Extension (GLX) |publisher=Massachusetts Department of Transportation}}

Pre-revenue service, where trains on the Union Square Branch were operated on a revenue schedule but without passengers aboard, began on January 16, 2022.{{cite magazine |title=MBTA Current Events |page=3 |magazine=Rollsign |date=November–December 2021 |volume=58 |issue=11–12 |publisher=Boston Street Railway Association}} On February 24, 2022, the MBTA announced that Lechmere and the Union Square Branch would open on March 21, while the Medford Branch would open in "late summer".{{cite press release |url=https://www.mbta.com/projects/green-line-extension-glx/update/green-line-extension-glx-union-square-branch-opens-march |title=Green Line Extension (GLX) Union Square Branch Opens March 21 |date=March 18, 2022 |publisher=Massachusetts Bay Transportation Authority}}{{Cite news |last=Lisinski |first=Chris |date=February 24, 2022 |title=Green Line Extension service to begin March 21 |url=https://www.wbur.org/news/2022/02/24/mbta-somerville-green-line-open |access-date=February 25, 2022 |website=WBUR}} Service to Union Square began on March 21 as scheduled.{{cite press release |last1=MacCormack |first1=Terry |title=Baker-Polito Administration Celebrates Opening of the Green Line Extension |url=https://www.mass.gov/news/baker-polito-administration-celebrates-opening-of-the-green-line-extension |publisher=Government of Massachusetts |date=March 21, 2022 |access-date=October 24, 2022 |archive-date=December 4, 2022 |archive-url=https://web.archive.org/web/20221204085822/https://www.mass.gov/news/baker-polito-administration-celebrates-opening-of-the-green-line-extension |url-status=dead }} In August 2022, the MBTA indicated that the Medford Branch opening was delayed to late November 2022 due to several factors including additional testing of the traction power system. The Union Square Branch was also closed from August 22 to September 18, 2022; the closure allowed for final integration of the Medford Branch, elimination of a speed restriction on the Lechmere Viaduct, demolition of the Government Center Garage, and other work.{{cite press release |url=https://www.mbta.com/news/2022-08-05/building-better-t-glx-medford-branch-open-late-november-2022-shuttle-buses-replace |title=Building A Better T: GLX Medford Branch to Open in Late November 2022; Shuttle Buses to Replace Green Line Service for Four Weeks between Government Center and Union Square beginning August 22 |date=August 5, 2022 |publisher=Massachusetts Bay Transportation Authority}} D and C branch trains served Union Square from August 6 to 21, 2022, while the E branch was closed for unrelated work, and primarily D branch service has served Union Square since September 19. The Medford Branch opened on December 12, 2022.{{cite press release |url=https://www.mbta.com/news/2022-12-12/mbta-celebrates-opening-the-green-line-extension-medford-branch |publisher=Massachusetts Bay Transportation Authority |title=MBTA Celebrates Opening of the Green Line Extension Medford Branch |date=December 12, 2022}}

Somerville signed a lease agreement with the MBTA for the Community Path in February 2023.{{cite news |url=https://mass.streetsblog.org/2023/03/01/somerville-approves-community-path-lease-agreement-opening-delayed-til-april/ |title=Somerville Approves Community Path Lease Agreement; Opening Delayed 'Til April |newspaper=Streetsblog Mass |date=March 1, 2023 |first=Christian |last=MilNeil |access-date=March 1, 2023}} The extension opened on June 10, 2023.{{cite press release |url=https://www.mbta.com/news/2023-06-09/glx-community-path-open-june-10 |title=GLX Community Path to Open on June 10 |date=June 9, 2023 |publisher=Massachusetts Bay Transportation Authority}} The Union Square Branch was closed from September 18 to October 10, 2023, during repairs to Squires Bridge, which carries the McGrath Highway over the tracks.{{cite press release |url=https://www.mbta.com/news/2023-08-28/september-service-changes-will-allow-crews-continue-improvement-work-across-mbta |title=September Service Changes Will Allow Crews to Continue Improvement Work Across MBTA System |date=August 28, 2023 |publisher=Massachusetts Bay Transportation Authority}} The closure was originally planned for July 18 to August 28, but was delayed and shortened due to public criticism.{{cite news |url=https://www.bostonglobe.com/2023/06/29/metro/that-new-green-line-branch-union-square-t-is-closing-it-42-days-this-summer/ |title=That new Green Line branch to Union Square? The T is closing it for 42 days this summer. |first=Daniel |last=Kool |newspaper=Boston Globe |date=June 29, 2023 |archive-url=https://web.archive.org/web/20230630062950/https://www.bostonglobe.com/2023/06/29/metro/that-new-green-line-branch-union-square-t-is-closing-it-42-days-this-summer/ |archive-date=June 30, 2023}}{{cite press release |url=https://www.mbta.com/news/2023-06-29/july-service-changes-will-allow-crews-continue-track-improvement-work-across-mbta |title=July Service Changes Will Allow Crews to Continue Track Improvement Work Across MBTA System |date=June 29, 2023 |publisher=Massachusetts Bay Transportation Authority}}{{cite news |url=https://www.wbur.org/news/2023/07/05/somerville-bridge-mbta-sumner-tunnel-delay |title=Project requiring Green Line Extension closure postponed to September |newspaper=WBUR |date=July 5, 2023 |first=Chris |last=Lisinski |access-date=July 6, 2023}}

In June 2023, the MBTA added {{convert|600|feet}} of temporary speed restrictions on GLX tracks – as slow as {{convert|3|mph}} – due to defects with the track gauge. This was increased to {{convert|1|mile}} in September 2023.{{cite news |url=https://www.bostonglobe.com/2023/09/26/metro/mbta-green-line-extension-new-slow-zones/ |title=New Green Line extension already so defective that trains are forced to move at walking pace |first=Taylor |last=Dolven |newspaper=Boston Globe Staff |date=September 26, 2023 |archive-date=September 27, 2023 |archive-url=https://web.archive.org/web/20230927022756/https://www.bostonglobe.com/2023/09/26/metro/mbta-green-line-extension-new-slow-zones/}} The speed restrictions were lifted in October.{{cite news |url=https://www.wbur.org/news/2023/10/11/boston-somerville-glx-union-square-slow-zones |title=MBTA Green Line service at Union Square reopens ahead of schedule with all slow zones lifted |newspaper=WBUR |date=October 11, 2023 |first=Katie |last=Cole |access-date=October 11, 2023}} Later that month, the MBTA disclosed that the too-narrow track gauge was known by the MBTA as early as April 2021. To fix the issues, 50% of Union Square Branch track and 80% of Medford Branch track needed to be regauged by moving the tie plates.{{cite news |url=https://www.bostonglobe.com/2023/10/19/metro/green-line-extension-update/ |archive-url=https://web.archive.org/web/20231019193119/https://www.bostonglobe.com/2023/10/19/metro/green-line-extension-update/ |archive-date=October 19, 2023 |first1=Taylor |last1=Dolven |first2=Laura |last2=Crimaldi |first3=Sean P. |last3=Murphy |first4=Hanna |last4=Krueger |newspaper=The Boston Globe |date=October 19, 2023 |title=Brand new Green Line extension in much worse shape than previously disclosed, T chief says}} The work began on November 27, 2023; it was not completed by the intended date of December 10.{{cite press release |url=https://www.mbta.com/news/2023-11-16/december-service-changes-will-allow-crews-continue-improvement-work-across-mbta |title=December Service Changes Will Allow Crews to Continue Improvement Work Across MBTA System |date=November 16, 2023 |publisher=Massachusetts Bay Transportation Authority}}{{cite news |url=https://www.bostonglobe.com/2023/12/21/metro/mbta-green-line-extension-issues/ |archive-url=https://web.archive.org/web/20231221182552/https://www.bostonglobe.com/2023/12/21/metro/mbta-green-line-extension-issues/ |archive-date=December 21, 2023 |title=The MBTA's new Green Line extension has a long history of trouble. It's still not fixed. |newspaper=The Boston Globe |date=December 21, 2023 |first1=Taylor |last1=Dolven |first2=Laura |last2=Crimaldi |first3=Sean P. |last3=Murphy}}

In December 2023, the MBTA Board voted to acquire a property to expand the vehicle maintenance facility for future two-car trains of Type 10 vehicles. A tentative settlement reached with the property owner will also allow pedestrian connections to be built between East Somerville station and the Inner Belt area.{{cite web |url=https://cdn.mbta.com/sites/default/files/2023-12/%236.%20Inner%20Belt%20Final%20Presentation%20to%20Board%20Public%20Session%20V12.12.23.pdf |title=Inner Belt Land Acquisition: Presentation to MBTA Board of Directors |first=Richard |last=Henderson |date=December 13, 2023 |publisher=Massachusetts Bay Transportation Authority}}

{{clear right}}

File:USQ D2.3 construction, September 2022.JPG

The GLX is expected to have substantial economic benefits for Somerville. Along with Assembly station, it will increase the proportion of the city's population within walking distance of rapid transit from 15% to 85%; {{convert|192|acres}} of land (mostly near Union Square) were opened for redevelopment in parallel with the project. Transit construction can result in gentrification – and displacement in turn – as wealthier residents seek to live close to stations, though this varies substantially depending on other factors like development planning.{{cite journal |title=How Does Light Rail Transit (LRT) Impact Gentrification? Evidence from Fourteen US Urbanized Areas |first1=Dwayne Marshall |last1=Baker |first2=Bumsoo |last2=Lee |journal=Journal of Planning Education and Research |year=2019 |volume=39 |issue=1 |pages=35–49 |doi=10.1177/0739456X17713619|s2cid=148788209 }} The 1984 opening of Davis station (Somerville's only transit station until Assembly station opened in 2014) resulted in gentrification and rising housing prices in the Davis Square neighborhood.{{cite journal |url=http://reconnectingamerica.org/assets/Uploads/kahnree2007.pdf |title=Gentrification Trends in New Transit-Oriented Communities: Evidence from 14 Cities That Expanded and Built Rail Transit Systems |first=Matthew E. |last=Kahn |year=2007 |volume=35 |issue=2 |pages=155–182 |journal=Real Estate Economics|doi=10.1111/j.1540-6229.2007.00186.x |s2cid=59143290 }}{{cite news |url=https://tuftsdaily.com/features/2017/12/05/living-near-tufts-no-longer-tough-part-town-davis-square-gentrified/ |title=Living near Tufts: No longer the tough part of town; Davis Square gentrified |first=Constantinos |last=Angelakis |date=December 5, 2017 |newspaper=Tufts Daily |access-date=November 28, 2021}}

Residents and politicians raised concerns about gentrification and displacement resulting from the project even before construction began.{{cite news |url=https://www.newspapers.com/clip/89733013/the-boston-globe/ |title=Big dreams in Somerville |first=Steven A. |last=Rosenberg |newspaper=Boston Globe |date=December 5, 2013 |pages=P1, [https://www.newspapers.com/clip/89733105/the-boston-globe/ P11] |via=Newspapers.com}} A February 2014 study found that 740 to 810 households in the GLX corridor were at risk of displacement from projected rent increases, up to 475 at risk from conversion of apartments to condominiums, and 245 at risk from expiration of housing subsidies. Property tax increases were not expected to cause significant displacement. Some 6,300 to 9,000 new housing units would be needed by 2030 to prevent additional displacement.{{cite web |archive-url=https://web.archive.org/web/20140706063021/http://www.mapc.org/sites/default/files/Dimensions_of_Displacement_Final_Draft_2_10_14.pdf |archive-date=July 6, 2014 |url=http://www.mapc.org/sites/default/files/Dimensions_of_Displacement_Final_Draft_2_10_14.pdf |title=The Dimensions of Displacement: Baseline Data for Managing Neighborhood Change in Somerville's Green Line Corridor |date=February 2014 |publisher=Metropolitan Area Planning Council}}

The areas around Union Square and East Somerville stations were expected to have the highest rent increases – up to 67% in some instances. The US2 mixed-use development in Union Square, which is primarily replacing light industrial buildings, is intended as an anti-gentrification measure by increasing housing supply and subsidizing nearby households and businesses at risk of displacement.{{cite news |archive-url=https://web.archive.org/web/20150709071210/http://www.bostonglobe.com/opinion/2014/06/30/somerville-the-little-city-that-could/1e287zFYLmzpZG4i2TjvQJ/story.html |archive-date=July 9, 2015 |url=http://www.bostonglobe.com/opinion/2014/06/30/somerville-the-little-city-that-could/1e287zFYLmzpZG4i2TjvQJ/story.html |title=Boston needs ideas — from Somerville |first=Paul |last=McMorrow |newspaper=Boston Globe |date=July 1, 2014}} By late 2014, both residential and commercial rents were rising more than typical in Union Square.{{Cite news |last=Kooker |first=Naomi |date=December 9, 2014 |title=Green Line plan brings economic tension to Union Square in Somerville |work=Boston Globe |url=https://www.bostonglobe.com/business/2014/12/09/green-line-extension-plan-brings-economic-tension-somerville-union-square/aataVlAvWcjqcWxmPRzk2J/story.html |archive-url=https://web.archive.org/web/20181118203205/https://www.bostonglobe.com/business/2014/12/09/green-line-extension-plan-brings-economic-tension-somerville-union-square/aataVlAvWcjqcWxmPRzk2J/story.html |archive-date=November 18, 2018}}

Title VI analysis conducted in May 2021 indicated that the project would result in "disparate benefit to nonminority populations and a disproportionate benefit to non-low-income populations" – primarily due to demographic changes in the project area since planning began – though both protected populations would see an overall increase in service.{{cite web |url=https://cdn.mbta.com/sites/default/files/2021-05/2021-05-24-fmcb-20-glx-title-vi-equity-analysis-ctps-findings.pdf |title=Green Line Extension: Title VI Service and Fare Equity Analysis |date=May 12, 2021 |first1=Steven |last1=Andrews |publisher=Central Transportation Planning Staff |first2=Blake |last2=Acton}} The MBTA Board voted to address the disparity by retaining service on the route {{MBTABus|80}} bus (which had been planned for discontinuance when the GLX opened) and as part of an ongoing bus network redesign.{{cite web |url=https://cdn.mbta.com/sites/default/files/2021-05/2021-05-24-fmcb-20-glx-title-vi-equity-analysis-accessible.pdf |title=GLX Title VI Equity Analysis |date=May 24, 2021 |first=Lynsey |last=Heffernan |publisher=Massachusetts Bay Transportation Authority}}{{cite news |url=https://www.boston.com/news/local-news/2021/05/25/mbta-green-line-extension-equity/ |title=MBTA finds that the Green Line Extension will disproportionately benefit richer, whiter riders |date=May 25, 2021 |newspaper=Boston Globe |first=Nik |last=DeCosta-Klipa |access-date=November 29, 2021}} By 2021, home sale prices in Somerville had increased by 40% since 2016.{{cite news |url=https://www.wcvb.com/article/real-estate-market-heats-up-as-end-of-green-line-extension-project-nears/36379560 |title=Real estate market heats up as end of Green Line Extension project nears |first=Katie |last=Thompson |date=May 10, 2021 |newspaper=WCVB |access-date=November 29, 2021}} Somerville was formerly popular with artists due to lower prices than Boston and Cambridge, but artists have reported that affordable studio space is largely nonexistent, in part due to GLX-related gentrification.{{cite news |url=https://www.wbur.org/news/2021/08/09/somerville-artists-studios-disappearing |title=In Somerville, Affordable Studio Space For Artists Is Rapidly Disappearing |date=August 9, 2021 |first=Jenn |last=Stanley |newspaper=WBUR |access-date=November 29, 2021}}

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{{Reflist}}

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{{Attached KML}}

• [https://www.mass.gov/green-line-extension-project-glx MassDOT project page]
• [https://www.mbta.com/projects/green-line-extension-glx MBTA project page]
• [http://www.somervillestep.org STEP (Somerville Transportation Equity Partnership)]
• 2014 animations: [https://www.youtube.com/watch?v=nuhM3Vxc_O8 Medford Branch], [https://www.youtube.com/watch?v=UYQsB3wQF84 Union Square Branch]

{{MBTA}}

Category:Green Line (MBTA)

Category:Railway lines opened in 2022

Category:Transportation in Cambridge, Massachusetts

Category:Transportation in Medford, Massachusetts

Category:Transportation in Somerville, Massachusetts

Category:Green Line Extension