This is a borderline God mode proposal: I was considering a LRT line running as a cut n cover, partially tunnel bored route from Central Square in Cambridge to Washington St and Mass Ave under Mass Ave (tunneling under Mass Ave bridge under the Charles).
This would replace a good chunk of the 1 and meant to replicate CT1. There could be a possible extension to BMC and Newmarket - to fully replicate the CT1 and to connect to a future Indigo line.
If this kept going, it could connect at Columbia Rd to proposed center-running LRT proposed by others.
This is kind of a mini Crenshaw K line - connecting to ends of a system on the west side.
Also, as a connector line - it would link red to green to orange to silver and indigo (eventually). If SL was converted to F Line to Nubian, then there would be an even better connection - not to get carried away.
This is a crazy pitch especially becausd I dont think the area is dense enough. Also - cost, engineering, politics.
Interesting proposal. Let's start with the good news:
First: it's pretty feasible on basic, mandatory-step-one "physically possible" grounds. The chosen route is nice and wide, no interacting with any of those nasty-hard-to-build under narrow streets some proposals rely on (including real-world proposals...looking at you, Essex St. Silver Line...) I'm not an engineer, but I do wonder about the feasibility of boring a tunnel under a river bridge (though I'm sure the people on the Cambridge-side shore of said bridge would be able to answer that concern), but it's not direct-constrained on the land immediately adjacent to the overwater section of the bridge, so it's probably quite feasible to tunnel just offset from the bridge if necessary.
Second: it hits lots of transfers to and from the radial lines along its route, providing ample connectivity. It's quite an alluring thing, a route that direct hitting that many transfer nodes with that much width to play with. Especially if it continued to JFK/UMass, it'd get you a large-segment circumferential route bracketed by the Red Line at both ends, potentially relieving some of the downtown transfer stress on the RL.
Now, the bad news:
First: the cost. Central Square has some problems as a starting point. The Red Line tunnel is already there under Mass Ave until Main Street, meaning you have two options, both of them annoying. You can either build your terminal underneath the existing Central station, which makes for a shorter transfer and better allows for future potential extension, but which requires deeper-down tunneling and underpinning the existing station and several hundred to a thousand or so feet of existing tunnel, which increases the cost. Or, you can build the terminal south of Main Street, where you could do it shallower and cheaper, though complicating the transfer by requiring either a long (and still not free) pedestrian tunnel or a kludgy surface transfer. The Charles River tunnel would be one of the T's longer water crossings, the river is quite wide there, which will increase the cost further. Utility would require transfers to the Green (at Hynes at the very least, where you at least don't have to underpin the entire station) and Orange (at Mass Ave, where you have to dig below the Northeast Corridor) and points beyond, all of which is a lot of money in tunnels and stations. All of which exacerbates...
Two: the connectivity problem. Mass Ave almost seems like it goes out of its way to avoid any of the major transfer nodes. Hynes, Symphony, Mass Ave OL, and Mass/Washington SL are
none of them major bus terminals, have no room to become major bus terminals, and are mostly (weirdly) about one stop away from a major bus terminal. That's a problem because the buses aren't going to be feeding into this line nearly as well as they are into others. So the double-transfer problem crops up; someone whose bus dumps them at Kenmore or Ruggles or Nubian would have to take the existing line one or two stops, then transfer to the new line. The existing 1 bus serves a more useful circumferential function than this proposal despite its 'worse' mode, in part because it can be fed by the big bus hubs at Nubian and Harvard. This can't do that. It just replaces the 1 bus with a more expensive, higher capacity (thus likely worse headways) mode along part of its route. Anyone whose destination isn't on the stretch between Central and Mass/Washington (or Newmarket slash JFK/UMass in a full-build version) would need to double-transfer, and they won't, they'll just ignore this line in favor of transferring at Park or DTX just like they do now.
Now, don't get me wrong, I like the idea of upgrading the Mass Ave corridor. I thought I recalled hearing something about them installing bus lanes, and if the MBTA wasn't so allergic to the very notion of street running, I could be intrigued by discussion of a surface LRT service of some kind. The circumferential service concept connecting the radial lines is genuinely beneficial and something the system absolutely could do with, but between the tunneling costs and the route missing both
all the major bus hubs
and Longwood Medical Area, I think it'd fail a cost-benefit analysis, especially compared to something lower-impact but much-cheaper like BRT-ing the 1.
(Not quite a pitch of my own, but I do wonder what people -
@Riverside for one - would think about the prospects of a [tunneled or surface] circumferential line that missed some or all of the bus hubs but hit the LMA. Is Longwood strong enough on its own that it'd be worth sacrificing some of the bus connections if it opened up the route possibilities?)