Getting Boston Moving: My Expansion proposals


Despite it’s challenges, maintenance backlogs, debt and safety record, the MBTA is a lifeline for the city of Boston, one that must be expanded over the next few years to help Massachusetts meet its climate goals, ease traffic congestion, and keep up with the growth of Boston.

The MBTA, or the Massachusetts Bay Transportation Authority is the transit network that covers the Boston Metropolitan Area.  The agency operates 4 rapid transit services – the red, blue, and orange lines, alongside the green line trolleys / Mattapan line.  The system was designed to be hub and spoke, meaning it disperses from Central Boston out to the suburbs on the outskirts of Boston.  This leaves many large gaps between subway lines near the end of their lines, and forces people to travel into downtown Boston to transfer between any of the rapid transit lines.

The Map

The Circle Line

The Circle Line has been one of the longest-proposed transit projects, just behind the Red-Blue connector and the Green Line Extension.  In my opinion, most proposals are flawed.  While the idea behind the proposal – linking the subway lines together without heading into downtown – is strong, that’s all the line is designed to do.  It services few new areas – increasing connectivity to areas that already have good transit service, while largely ignoring transit deserts.

When I think of circle lines, I immediately jump to the Overground network in London.  The network operates lines in a nearly complete loop (you need to change trains at Highbury & Islington to complete the full loop), however, it has branches off of the loop expanding service into suburbs on both sides of the Thames river.

My solution is to break the circle line apart, and expand it out to Waltham, Lynn, and Porter – the last 2 utilizing abandoned rail right of ways to save money.

Yellow line – A branch

Starting in Waltham, a major bus hub and commuter rail transfer, all 3 lines would follow the Charles River, paralleling a small part of the Charles River greenway – roughly at grade level.  After Watertown Square, the line would need to dip into a short tunnel under Arsenal street, heading above ground shortly before its stop at Arsenal Yards, and remaining above ground onto its first major Charles river crossing.  Branch A diverts away from Branch B to service the Harvard campus in Allston, where green line service has long been proposed.  The stations in Magazine Square and Cambridgeport give rapid transit services to neighborhoods that despite being less than one mile from the Back Bay, are only served by slow buses – the infuriatingly slow kind.  It would then join onto the Grand Junction line, following it through its Kendall / MIT station onto an elevated viaduct that takes it to Lechmere and Charlestown.

The stretch between Community College and Airport would need to be tunneled, assuming shutting the line down so a drawbridge can open is off-limits.  It would remain in its tunnel under the airport blue line station and under the Chelsea creek (A known pain-point for the SL3).  The line would utilize the SL3’s dedicated bus lanes until Chelsea station, saving money.

Ideally, the Everett bit (South Everett and Wehner Park) would use cut and cover – hopefully not completely breaking the bank.  The remaining leg up to Lynn would follow the Northern Strand bike trail.  [Bike trails converted to rail would remain]

Yellow line – B branch

The B branch is just the circle line, but with a twist at the southern end.  Rather than continuing around in a loop via Longwood & Cambridge, it joins the Fairmount line right of way, with an extension to Dedham mall.

Breaking up the loops fixes a large majority of the operational loop associated with loops.  Going back to the London Example, their loop line, the circle line, no longer operates in a loop.  This is due to a number of factors that make loop lines tough to operate – maintaining even spacing, managing operator breaks, and getting malfunctioning equipment off of these lines without causing cascading delays can be significantly tougher than on their terminal-ended counterparts.

The extension to Dedham solves another large operational problem, in conjunction with the orange line, of trying to find space to store all of the trains needed for operating the line.  I can’t think of a reasonable spot in downtown Boston where that could be done at a decent price.

Yellow line – C branch

This would just be a reactivation of the old, abandoned, Watertown branch.

Spacing is very tight in downtown Watertown, meaning without widening the right of way, the rail trail currently in place would need to go.  If this were ever built, I’d love to see a similar approach to the GLX taken, where the right of way is widened enough to fit in a wider bike trail.

The New Blue Line

Vanshnookenraggen has an excellent post on the future of the green line.  One of the ideas that he floated in that post was a green line tunnel under Huntington Ave (the street the E branch runs down) and a new redundant green line tunnel under Stuart St rather than Boylston St.  Both are awesome proposals, and I highly recommend reading it!

I figured: why not take it a step further and combine it with a frequently mentioned plan of converting the MBTA D branch into an extension of the blue line.

Notably, it diverts off Huntington Avenue, stopping closer to the center of the Longwood Medical Area.  The station would be located closer to Simmons University / Harvard Medical School rather than directly under the existing station.  

The final notable difference is the addition of a branch to Needham – a short 2 mile branch purely designed to connect the D branch to the Needham line.

The Remaining extensions

The GLX to West Medford and Porter, and the blue line to Lynn are just general, run-of-the-mill transit extensions that have been long proposed by people much more experienced than me.


A perfect analogy that I’ve heard from many people in the transportation sphere is that the MBTA needs to be able to walk and chew gum at the same time.  It’s important for the MBTA to maintain its current infrastructure at the same time as its expanding.  If it doesn’t expand, the system will be stuck in the past, not adapting well to new travel patterns, or going to the places that people actually want to go to.

Next week, I plan to release my commuter rail expansion plans, which are just as ambitious.  It has a bunch of existing, long-studied plans on it, alongside my own ideas for expansion!

Thanks for reading!


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