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Red Line-Blue Line Connector


The Blue Line and Red Line are currently the only MBTA subway lines without a direct transfer to each other. Various proposals to connect the two lines together exist, including proposals to extend the Blue Line to the Charles/MGH station on the Red Line to create a free transfer, known as the Red Line-Blue Line Connector, or to construct pedestrian tunnels linking the State station on the Blue Line to the Downtown Crossing and Park Street stations on the Red Line, creating a Downtown "superstation". Today, transfers between the Red and Blue Lines can be made by riding the Green Line one stop between the Government Center and Park Street stations, or by riding the Orange Line one stop between the State and Downtown Crossing stations. However, these transfers require passengers to navigate multiple passages and staircases and increase rush-hour congestion on subway lines in the Downtown subway stations, contributing to delays in subway service.

As part of a lawsuit settlement relating to air quality mitigation for the Big Dig highway tunnel project, the Commonwealth of Massachusetts agreed to build a direct transfer connection between the Blue and Red Lines. The Blue Line would be extended beyond Bowdoin station, continuing 1500 ft beneath Cambridge Street to a new underground terminal at Charles/MGH, connecting to the existing elevated Red Line station. In addition to providing a direct transfer between the Red and Blue Lines, this would allow passengers from the North Shore of Boston to reach the Massachusetts General Hospital area directly without further transfers. The MBTA estimated this connection would induce 12,000 new daily boardings at Charles/MGH station, reducing vehicle miles traveled by 5,250 per day.

After failing to take any action for over a decade, and under threat of further lawsuits, the state finally agreed to start detailed engineering design for such an extension. Construction was expected to take six years, but a start date and funding scheme were never announced. The MBTA ultimately decided not to complete the design work necessary to build the Red/Blue Connector, as funding for constructing it was seen as an impossibility. The possibility of a public-private partnership (P3) to advance the project was studied in 2013. The U.S. Environmental Protection Agency formally released the state from its design obligation (as a Big Dig mitigation project) in 2015.

The Blue-Red Connector was mentioned in Boston's bid for Amazon HQ2 as a "clear goal" for the state. In 2018, the state commissioned a $50,000 study by the engineering firm Vanasse Hangen Brustlin (VHB). It estimated a much lower cost for the tunnel—between $200 million and $350 million, depending on the construction method used—and a total project cost of up to $500 million. The lower cost is due to consideration of the cut and cover construction technique, which would be cheaper but more disruptive to vehicle traffic.

The Summer 2018 draft of the MBTA's 2040 planning document includes a potential underground pedestrian walkway between State and Downtown Crossing stations, though the technical feasibility had not been evaluated.

Previous Connection
A physical rail connection between the Red and Blue Lines existed in the early part of the 20th century (prior to the MBTA assigning the color designations of the subway lines). Railcars from what is today the Blue Line could emerge from a ramp portal surfacing between Joy Street and Russell Street, just beyond Bowdoin station. The railcars would run on former streetcar track down Cambridge Street and then most of the distance to the western end of the Longfellow Bridge, connecting to what is now the Red Line just east of its Cambridge Subway portal, near what is now Kendall/MIT station. Because the tracks were unpowered, individual cars had to be towed along the street at night. This connection was never used in passenger service, but was used to transport Blue Line cars to the Eliot Street Yard maintenance shops then located near Harvard Square station. When the Blue Line eventually got its own maintenance shops, the connection was removed and the ramp portal was permanently covered in 1952.