Union Square station (Somerville)
| Company type | Light rail station |
|---|---|
| Industry | Public transportation |
| Founded | March 21, 2022 |
| Headquarters | Somerville, Massachusetts , United States |
Area served | Somerville, Massachusetts |
| Products | Light rail transit services (MBTA Green Line) |
Union Square station serves as a light rail stop on the Massachusetts Bay Transportation Authority (MBTA) Green Line within the southeastern Somerville neighborhood known as Union Square. This accessible terminus consists of a single island platform positioned between two tracks on the Union Square Branch, which runs parallel to the Fitchburg Line. The station commenced operations on March 21, 2022, as part of the Green Line Extension (GLX) project that introduced two new northern branches to the Green Line network.
The site originally hosted a station on the Fitchburg Railroad named Prospect Street, established in the 1840s and renamed Union Square around 1875. This older station ceased operation and was demolished by 1938. Although various Green Line extension plans emerged throughout the 20th century, a dedicated Union Square branch was only conceptualized in the early 2000s. After assessing multiple potential locations, officials selected the Prospect Street site alongside the Fitchburg Line corridor in 2009. The MBTA pledged in 2012 to open this station by 2017 and awarded a construction contract in 2013.
Due to escalating expenses, a comprehensive review of the GLX project occurred in 2015. A streamlined station design was unveiled in 2016, followed by a combined design-build contract awarded in 2017. Construction kicked off in early 2020 and reached near completion by late 2021. Initially, service was provided by the Green Line E branch, but currently, the station is served by the Green Line D branch. A major development initiative is ongoing adjacent to the station.
Station design
Located just east of the Prospect Street bridge and approximately south of the Union Square intersection, Union Square station lies along a northwest–southeast axis defined by the Fitchburg Line. The two-track Union Square Branch of the Green Line runs north of these commuter rail tracks. The station includes a single island platform measuring approximately long and wide, situated about east of Prospect Street between the Green Line tracks and fully sheltered by a canopy.
The platform height is set at for accessible boarding on existing light rail vehicles (LRVs), with provisions to raise it to for future level boarding compatible with Type 9 and Type 10 LRVs. It is also engineered for potential extension up to in length. A starter booth is located at the platform’s eastern end, with an emergency exit path leading toward Allen Street.
The entrance plaza is positioned east of the Prospect Street bridge beside a utility structure. A pedestrian walkway connects this plaza to the platform and includes fare vending machines near its western end. Tail tracks extend alongside this walkway, designed to accommodate future extension toward Porter station. Immediately north of the plaza lies "Station Plaza," developed concurrently with an adjacent building. The primary entrance provides access from Prospect Street via an elevator and stairs that connect to the bridge.
Public art installations feature Passage, a sculptural archway created by Matthew Trimble spanning over the platform walkway, as well as murals incorporated into station signage. Bicycle amenities include racks for 34 bicycles within the entrance plaza and a covered shelter capable of housing an additional 86 bikes. Several MBTA bus routes serve stops located near this station.
Railroad station
The Charlestown Branch Railroad reached Somerville in 1841 and commenced operations on January 5, 1842, before being incorporated into the Fitchburg Railroad in 1846. Shortly thereafter, Prospect Street station opened near Medford Street (present-day Webster Avenue) to serve the Sand Pit Square neighborhood. During the mid-1800s, it mainly accommodated trains on the Lexington Branch. In the 1860s, the adjacent square was renamed Union Square, and by approximately 1875, the station adopted the Union Square designation.
By 1849, Prospect Street had been elevated onto a bridge spanning the railroad tracks, whereas Webster Street continued to cross at grade level. Beginning in 1900, Somerville initiated plans to eliminate eleven grade crossings, including five along the Fitchburg mainline. A 1906 proposal suggested raising 1.8 miles of track to remove these crossings; however, this plan was ultimately not implemented.
After the removal of the Somerville Avenue grade crossing in 1908–09, construction commenced in April 1911 to elevate Webster Street above the railroad. The elevation project raised Webster Street and nearby structures by roughly 20 feet, while the tracks were lowered slightly. A specialized bridge was built to support a heavy water main. The original station building, which was 67 years old at that time, was replaced with a larger facility located on the southern side of the tracks; this work was completed in December 1911.
Competition from horsecar and later electric streetcars caused a decline in ridership; by 1917, Union Square and Somerville stations were served by only four to five daily Watertown Branch trains alongside some off-peak locals. Due to decreasing passenger numbers, the station building was converted for manufacturing use by 1924. Service had dwindled further by 1929 to just one outbound and two inbound Watertown Branch trains. Passenger operations ceased entirely on July 9, 1938, coinciding with the closure of the Watertown Branch. The station structure was demolished sometime between 1936 and 1940.
The idea of adding an MBTA Commuter Rail Fitchburg Line stop at Union Square has resurfaced periodically; as of 2003, a station was anticipated within five years. According to the 2004 state Program for Mass Transportation, such a facility would attract about 390 daily riders. In 2012, a Union Square commuter rail station was proposed as a temporary air quality mitigation strategy due to delays in the Green Line Extension project; however, MassDOT rejected this plan owing to high costs and scheduling challenges.
Alignment
Proposals for extending rapid transit northwest from date back to 1922. Throughout the twentieth century, various plans suggested extending rapid transit along the Boston and Maine Southern Division (currently known as the Lowell Line) toward or beyond ; notably, the closest station to Union Square on this line was approximately eastward. In the 1980s, corridor studies considered a direct extension reaching Union Square as an option. A state agreement made in 1991 with the Conservation Law Foundation specified a "Green Line Extension To Ball Square/Tufts University". The 2003 Program for Mass Transportation evaluated potential Green and Blue Line extensions to , including routes diverging from the Lowell Line right-of-way to directly serve Union Square.
An updated agreement in May 2005 incorporated a Union Square branch into the Green Line Extension plans. The Beyond Lechmere Northwest Corridor Study, conducted as a Major Investment Study/Alternatives assessment, examined multiple light rail and bus rapid transit alternatives, including one featuring a branch to Union Square. In October 2006, Massachusetts’ Executive Office of Transportation and Public Works submitted an Expanded Environmental Notification Form (EENF) that identified a Green Line extension with branches to Medford and Union Square as preferred options; notably, the Union Square Branch was planned along the Fitchburg Line right-of-way. Later that December, environmental regulators required that a Somerville Avenue alignment for this branch be analyzed within the draft environmental impact report (DEIR).
By early 2008, three potential alignments were under consideration: a surface route following the Fitchburg Line east of Prospect Street; another surface alignment along Somerville Avenue west of Prospect Street; and a single-track loop combining these two routes with an underground station beneath Prospect Street south of Somerville Avenue. Official confirmation of Union Square as a future station site occurred in May 2008. Additional tunnel options for an underground station at Union Square—either involving a short tunnel near Prospect Street or an extended tunnel beneath Somerville Avenue—were studied that year but deemed not cost-effective.
Station design and contracts
The Draft Environmental Impact Report (DEIR) published in October 2009 favored the Fitchburg Line alignment because it offered cost savings, enhanced reliability through grade separation, and required fewer property acquisitions compared to other options. Initial designs featured a curved platform equipped with faregates positioned at the western end, alongside a two-story station structure that connected to the Prospect Street bridge and provided direct platform access from the north.
By May 2011, modifications shifted the platform further east and moved the kiss-and-ride zone to the north side of the headhouse. In February 2012, plans proposed an expanded upper-level headhouse as the main entry point, enabling closure of the lower entrance to facilitate a possible future extension to . Updates in June 2013 eliminated a mechanical penthouse, revised lobby layouts, and introduced bicycle parking near the upper entrance.
In August 2012, an agreement among Somerville, MassDOT, and MBTA stipulated that the City would purchase $8 million worth of land for the station through the Somerville Redevelopment Authority while granting MBTA a permanent easement; transit-oriented development rights above would remain with the City. Both MBTA and MassDOT pledged to handle site remediation, initiate construction by spring 2014, and aim for station operation by late 2016 or early 2017.
Somerville authorized an $8 million bond in October 2012—allocating $6 million for land acquisition and $2 million toward cleanup and planning efforts. The North Prospect block was acquired via eminent domain for $4.5 million in June 2013, with property clearances completed by August. Additionally, the city secured a $1 million EPA grant dedicated to environmental remediation.
In September 2013, MassDOT awarded a $393 million contract spanning 51 months for Phase 2/2A construction, covering Lechmere station, the Union Square Branch, and the Medford Branch segment up to Washington Street; these stations were slated to open in early 2017. Cleanup activities commenced in September 2014, with final station designs completed by late that year.
Redesign
In August 2015, MBTA disclosed that Phase 2A expenses had escalated dramatically from $387 million to $898 million, triggering a thorough reassessment of the Green Line Extension project. By December 2015, MBTA ended contracts with four firms and paused awarding new ones while allowing ongoing work to proceed. Considerations included canceling the project or removing the Union Square Branch to control costs.
In May 2016, boards of MassDOT and MBTA approved a value-engineered redesign aimed at reducing expenditures. The stations were simplified to resemble surface stops on the Green Line D branch by eliminating canopies, faregates, escalators, and several elevators. At Union Square station, entry was confined to the plaza north of the platform, removing direct access from the Prospect Street overpass. These cutbacks drew criticism from community members and elected officials concerned about accessibility issues—particularly reliance on extended ramps rather than elevators. MBTA then announced a revised opening timeline targeting 2021.
A design-build contract was awarded in November 2017. The selected design restored six features previously removed, including full-length canopies at every station. Station design advanced from no completion in March 2018 to full finalization by October 2019. The finalized plan relocated a utility building between tracks to maintain flexibility for potential future extensions.
Redevelopment
The inauguration of the station triggered extensive redevelopment efforts in Union Square and its surrounding neighborhoods. In 2009, zoning changes were implemented to designate commercial corridors and sites suitable for transit-oriented development; subsequently, a 2012 revitalization strategy appointed a lead developer for the area. Similar to the broader GLX project, the Union Square redevelopment encountered opposition from community members concerned about gentrification and the displacement of existing residents. A 2014 analysis anticipated that rents near the Union Square and East Somerville stations could rise by as much as 67%.
The USQ mixed-use project, which replaced former light industrial facilities, seeks to address displacement risks by increasing housing availability and providing subsidies to at-risk households and businesses. Despite these initiatives, by late 2014, rental rates for both housing and commercial spaces in Union Square were climbing at a pace exceeding regional averages. In November 2019, USQ developer US2 pledged to finance an elevator linking the station with the Prospect Street bridge. Construction of the initial new buildings adjacent to the station commenced in 2021, with completion targeted for 2022–23.
Construction and opening
The official groundbreaking ceremony occurred on June 25, 2018. Following the completion of design work, foundation construction started in January 2020. By early August 2020, the station platform had been poured, with canopy assembly beginning in September. Track installation was completed in October 2020. By April 2021, a signal hut was installed, and overhead catenary wires were added in May. Although elevator access to the Prospect Street bridge experienced delays, accessible pedestrian pathways remained available. Electrical installations began mid-2021; by November, canopy lighting and next-train arrival displays were operational.
Initially, plans called for the E Branch to serve Union Square. However, in April 2021, the MBTA announced that the D Branch would instead provide service to this station. Despite this change, service began with E Branch trains until testing on the Medford Branch commenced. The station's opening was originally scheduled for October 2021 but was postponed to December 2021 due to supply chain disruptions and then further delayed until March 2022 because of issues with a power substation. Train testing started in December 2021, followed by pre-revenue operations beginning January 16, 2022.
The Union Square Branch officially launched on March 21, 2022; elevator service became available in late April. From August 6 through August 21, 2022, C and D branch trains served Union Square while E branch maintenance was underway. The branch then closed from August 22 to September 18 to complete integration with the Medford Branch and finalize infrastructure upgrades. After reopening, a combination of D and E branch trains operated at Union Square until November 1, when E branch pre-revenue service commenced on the Medford Branch.
On April 20, 2023, the temporary ramp connecting to Prospect Street was closed for construction of a permanent walkway; both the Station Plaza and permanent path opened on October 23, 2023. The branch was again closed between September 18 and October 10 for repairs to Squires Bridge spanning the tracks. This closure was initially planned for July–August but was postponed and shortened following public feedback.
Local authorities have suggested extending service further toward Porter. In February 2022, Cambridge City Council requested that construction activities around Union Square be managed so as not to impede such an extension.