The Red-Blue Connector: A half-mile of subway that benefits an entire region

November 10, 2025

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The Red-Blue Connector: A half-mile of subway that benefits an entire region

November 9, 2025

By Will Palmer, Elias Fen, and James Aloisi

How long is too long to wait for all subway lines on the MBTA to be connected?

100 years?

This December, it will be 101 years since the Boston Globe first reported on the idea to connect the MBTA’s Red and Blue lines, noting that riders “using either the East Boston Tunnel [the Blue Line] or the Cambridge Subway [the Red Line] could change cars at Charles St, instead of transferring at Scollay Square and Park Street, the most congested parts of the whole system … This would have a distinct tendency to remove this congestion and would therefore be a highly desirable end in itself.”

A century later, the Globe’s description remains accurate: the Red and Blue lines remain the only two subway lines on the T that do not connect. Riders must make two zigzag transfers, using the Green or Orange lines, to travel between them. Not only is it inconvenient for riders, it also increases congestion and decreases capacity at Park Street and Government Center. These pressures on system capacity will only worsen with time.

It’s easy to look at the short length of the proposed Red-Blue Connector – less than half a mile – and mistake it for a project with small impact. Nothing could be further from the truth. Connecting the Red Line and Blue Line is a small project with a huge impact, and the time to do it is now, as Massachusetts General Hospital is in the process of rebuilding its campus facing Cambridge Street above the proposed subway connection.

Today, many of the region’s major job centers and key destinations, like the Longwood Medical Area, Back Bay, and Downtown Boston, can all be reached from every corner of the rapid transit network with at most a single transfer. Employers in these areas (and indeed anywhere along the Green and Orange lines) can therefore leverage excellent transit access to attract talent from across the region.

Employers in Cambridge, however – including in Kendall Square, one of Greater Boston's biggest job and innovation hubs – are systemically disadvantaged in this respect. Unlike their peers, these businesses, labs, and schools can't effectively appeal to some of the densest neighborhoods in the region, in East Boston, Revere, and surrounding communities. Both employers and residents suffer from suboptimal access to transit and opportunities, due to the gap separating the Red and Blue lines.

Many riders endure this tedious commute nevertheless, straining all other subway lines in the process. As described by the Globe a century ago, these riders have no choice but to squeeze on to already-crowded Green and Orange Line trains, and already-crowded platforms at Park Street and Downtown Crossing stations, all because of this 2,500-foot gap in our subway system.

The Red-Blue Connector closes this gap. It balances capacity and mobility on our rapid transit network, gives Kendall employers the benefit of better access for potential employees, and gives Blue Line riders better access to jobs in Kendall and elsewhere along the Red Line. Even riders who never set foot on the Blue Line would benefit, as crowding is reduced on trains and platforms throughout downtown.