Great ideas,
@The EGE! Some more specific comments:
The intention of that is not to serve as an Urban Ring, but to create a more meshed network where not every line has to go through downtown.
I definitely agree with this: It's worth considering subway trunks that do not necessarily go through the narrowly defined "Downtown Boston", or the Shawmut Peninsula.
That's what I like the most about the Kendall-Back Bay idea -- it double duties in both:
- As an "extended downtown" radial trunk, without deviating too far from the core downtown; (In comparison, a line through LMA gives up too much downtown-oriented traffic)
- As an "inner ring" that shuffles riders across lines, while still passing through important nodes and offering enough time savings.
I'd say that there are still available alignments through the "core downtown", however. The most popular alignments are essentially given by the NSRL studies:
- Central Artery (South Station - Aquarium - North Station)
- Congress St (South Station - Post Office Sq - North Station/Haymarket)
One of them will presumably be taken by NSRL, but whichever remaining alignment makes total sense for rapid transit. While they're somewhat duplicative to the Green and Orange lines, both have unique and intriguing benefits.
In a world where we can afford this "final core downtown trunk", my preference is to connect the Chelsea-Tobin Bridge line to it instead of to Kendall-Back Bay.
But I agree that if we can only afford one new north-south subway east of Mass Ave
(and even that may be a stretch), this is the best.
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There are three likely north-south corridors through Everett, northern Chelsea, and Revere: Broadway, US 1, and Broadway.
US 1 gets chosen a lot on crayons because it splits the difference between the Orange and Blue lines, but it doesn't hit the main nodes. I think it's justifiable to hit both Broadway corridors, since it puts most of the area within walk/bike radius of a station rather than still requiring bus for most trips.
At least in my view, Route 1 is almost entirely a matter of cost savings. An El above Route 1 will likely be an order of magnitude cheaper than subways under either Broadways, given similar distances. Route 1 can also recoup the rider base of the 111 bus, which seems quite transit-friendly. But in a more idealized world, I agree that the two Broadways are better.
I'll also highlight:
A radial Everett - Chelsea - Tobin line (as you've shown) is absolutely worth considering. It's somewhat roundabout for Everett, but much better than no radial service at all.
There's a bit of choose-your-own-adventure with the north ends of the branches. The Everett branch could terminate at Overlook (as shown here) with a possible park-and-ride, continue north to Saugus, turn east earlier to hit Linden Square and Northgate, or even turn west to Malden. The Revere Branch could terminate at Northgate (as shown here) or beyond, or turn east to Wonderland, or head northeast to Lynn.
Ending the Everett branch at Overlook is a unique idea, and probably driven by the housing developments there. I don't think it's a good P&R location, though: you need new ramps, and nearby residents are likely to complain about a new P&R at what's otherwise well inside a housing project.
IMO, Northgate is a better P&R position; or, if you still want to serve Overlook, you can continue north of Route 1 to the suburban mall
(Lowe's), which also has existing ramps to Route 1. Both locations combine parking with existing commercial activities, and offer room for denser redevelopment.
On station placement in Chelsea, I feel quite strongly that the most "central" Chelsea station should be on a trunk, not an individual branch; and that it should be at either Chelsea Sq (
2nd St) or Bellingham Sq (
Chelsea City Hall), the two main commercial areas of Chelsea, or somewhere in between. Admiral's Hill is too sparse, and the denser Downtown Chelsea shouldn't get only half the capacity.
In my crayons, I generally put the stop at 4th St or 5th St, which also approximately maximizes coverage in the 1/2-mile walkshed. It should be feasible to swing back to Everett from there -- even by following Route 1 as an El, and especially if you're using TBM.
On the other hand:
I don't love having only one branch connect with regional rail in Chelsea, but I don't think it's the end of the world either.
That I agree with. While there are good chances for TOD at the Mystic Mall / "Chelsea Market" station, geometry really hurts it here, especially for the Revere Broadway branch.
What I do love is the connection at Admiral's Hill. The TBM from one of the branches turns southeast and runs through Eagle Hill and Logan, then under the harbor to the Transitway. Direct graded-separated connection from the northern suburbs to the Seaport, Eagle Hill added to the subway network, and direct grade-separated Logan access.
The UR connection is an interesting idea, and really showcases the power of not being limited to existing ROWs (Grand Junction) when you build a subway.
(Even though the Eastern Ave station does deserve some form of good service.)
That said, if I were to build one single river crossing in this area, my pick would actually be the
"cross-Charlestown subway": Airport Terminals - East Boston - Charlestown - Sullivan. This actually functions as an effective circumferential route between OL and BL, and allows efficient Malden-Airport trips in ways that few other alignments can. Given the expense of a river crossing, I feel this offers better value for the whole region than one that mostly benefits Chelsea (and your Teal Line by extension), if we have to choose.
(Chelsea will still have the 104.)
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I'm inclined to have separate Copley and Back Bay stations; the lines are ~1000 feet apart, which would make for some long transfers. This would also reduce the crowding on the platforms.
My rationale for a combined Copley-Back Bay station was largely feasibility and cost. Copley station, in particular, can't be placed north of Boylston St due to narrow streets there and proximity to Old South Church. The Boylston-St James block is much wider, but still next to Boston Public Library (and there may be impacts to Trinity Church as well). For these reasons, I had eyed on the St James-Stuart block as the station site, which argues more strongly for a combined station.
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There are various possibilities for interacting with a potential light rail branch to Nubian - the light rail line could share a four-track subway, or run on the surface since it wouldn't be taking all the bus transfers at Nubian.
While there are clear benefits of running on Harrison Ave (closer to Boston Medical Center and BU Medical Campus), I doubt that a surface light rail can run there given narrow streets: Washington St is much better for a streetcar. So if a surface streetcar is included
(which is a good idea in general), I'd have different alignments, with the streetcar on Washington and the Back Bay subway on Harrison, Albany, or even I-93.
(The calculus changes if you want the LRT branch to also be a subway.)
There are also possibilities for a southern branch - to Southie via Andrew or Broadway, or the LMA via Roxbury Crossing, or down Geneva or Talbot towards the Red Line. I didn't include any of them here.
Another possibility is the "Red X", where this line can head to JFK/UMass
(or possibly Fields Corner) and take over one of the Red Line branches, allowing frequency increases for both Ashmont and Braintree.
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This seems about the right stop spacing, but you could justify more or fewer stops.
Assuming the Teal Line is fully underground, it seems like this would be easily justified if Fairmount Line never gets upgraded to proper rapid-transit-level* service, but more questionable if it does. Two "rapid transit" lines in close parallel here doesn't seem worth it, even after considering Blue Hill Ave being a successful transit corridor. I prefer terminating the line around the Four Corners/Geneva station (or further southeast to Fields Corner).
(However, I have somewhat low confidence on this, and I wouldn't be totally surprised if a BHA subway is still worth building even after Fairmount improvements.)
* "Rapid transit level" here refers to trains every 6-8 minutes or less, and ideally with NSRL to provide connections to the Green, Orange and possibly Blue lines.
