Redesign the Urban Ring

[Teban54]

However, I feel like there's a glaring flaw with this analysis, which is that it entirely excludes CR transfers. On an average weekday in Fall 2024, ~6,800 passengers per day boarded the CR at Back Bay (And curiously, around 7,100 alighted.) I don't know how many of those passengers went and transferred to the OL or GL at Copley, but given that Back Bay isn't that strong of a employment node, it's probably a very significant chunk. If even half of those passengers are removed from Back Bay's subway ridership, since for the most part they don't care where they transfer to the Urban Ring, the disparity between BU+Longwood and Back Bay decreases. I will say however, this doesn't really touch the point about strong Back Bay-Cambridge demand.

That's a great point! There are two ways of accounting for CR transfers:

1. Use the 2015-17 Passenger Survey to get the number of subway riders at Back Bay, Copley and South Station who came from commuter rail.
2. Use the 2018 Commuter Rail ridership counts to get total commuter rail ridership at these stations, then use the 2015-17 Passenger Survey to estimate the percentage of CR riders that transferred from rapid transit.

Granted, both are pre-Covid data which differ significantly from today's commuter rail ridership patterns, and neither account for Amtrak - but that's the best we can do.

Station	Back Bay	Copley	South Station (RL only)
Fall 2024 weekday ridership *	10493	9955	15901
Fall 2019 weekday ridership *	16727	13899	27214
(Method 1) Number of riders from CR, 2015-17 **	5358, 34.4%	1050, 8.4%	10170, 34.6%
(Method 1) "Pure rapid transit" riders, Fall 2019 (Simple subtraction)	11369	12849	17044
(Method 1) "Pure rapid transit" riders, Fall 2019 (Applies 2015-17 percentage to 2019 ridership)	10977	12734	17792
(Method 1) "Pure rapid transit" riders, Fall 2024 (Applies 2015-17 percentage to 2024 ridership)	6886	9121	10396
(Method 2) Total CR ridership, 2018 *	8747	N/A	27530
(Method 2) Number of CR riders from subway, 2018 (see spoiler)	3316	N/A	8377
(Method 2) "Pure rapid transit" riders, Fall 2019 (Simple subtraction of 2018 numbers)	13411	N/A (13899)	18837
(Method 2) "Pure rapid transit" riders, Fall 2024 (Applies 2019 % of pure riders to 2024 ridership)	8413	N/A (9955)	11006

* Average between boardings and alightings. South Station figures include transfers from Silver Line SL1/2/3. (Note that Back Bay has much more alightings than boardings in 2024, and South Station has more alightings than boardings in 2019.)
** Percentages are computed as (CR transfers) / (accessing the station as first MBTA mode + bus/SL transfers + rapid transit transfers + CR transfers).

Spoiler: CR riders and subway transfers at South Station and Back Bay

Completely excluding CR riders knocks down Back Bay's (and South Station's) rapid transit riderships by 20-40%, and Copley's ridership by less than 10%.

But this doesn't change the main conclusions from the earlier analysis:

• Each of Back Bay and Copley stations still has ridership several times higher than LMA. (The latter is ~2,400 between the three D/E branch stations.)
• Copley alone still has ridership comparable to Kendall, and the combined Copley-Back Bay ridership still surpasses Kendall.

Another point is that considering CR transfers may make an even stronger case for a "ring" / circumferential route through Back Bay. It captures a larger share of CR riders at Back Bay, compared to separate Urban Ring stations at Ruggles and Lansdowne (the latter may not even materialize), while offering a much more direct route to Kendall. This route is more effective at rerouting CR - South Station - Kendall trips, relieving pressure on the core segment of the Red Line.

And back to something I mentioned briefly in my previous comment, Mass Ave is right there. Light rail along the route of the 1 would go a long ways towards serving that Back Bay demand plus that Cambridge to Symphony demand that actually outpaces demand to LMA.

If we're explicitly aiming for a low-cost, not-God-mode proposal, then I agree that Mass Ave surface LRT/BRT is the best compromise to meet Cambridge-Back Bay demand.

But if we broaden our scope to more aggressive, imaginative and costlier proposals, I'd argue that a direct route to Copley-Back Bay stations is the way to go:

• Better destinations: Hynes Convention Center is too far from the center of the Back Bay neighborhood. Likewise, Kendall (or even Tech Square) stations serve the main job destinations much better than Mass Ave (Central-MIT). You can even say that Symphony is not ideal.
• Reliability: A Mass Ave surface line will likely be too slow, and I'd wager that it's only capable of handling "local" demand. This makes it less attractive for replacing downtown transfers.
• Network effects: A Kendall-Back Bay line has much better Commuter Rail integration and relieves the Grand Junction line from many duties, in ways that a Mass Ave line doesn't.

That said, in a low-cost world, it's possible that BRT may be the best way to go for Mass Ave:

• The key challenges for any Mass Ave surface route are dedicated transitways and (hopefully) signal priority. If you can tackle these, BRT and LRT can be equally reliable.
• More importantly, BRT has much greater flexibility for branching. The nature of Mass Ave -- many strong nodes that are offset from the corridor -- induces many plausible branches, which favor BRT over LRT:
  • South: Back Bay (proper), LMA, Ruggles, Kenmore/BU, JFK/UMass or Andrew
  • North: Harvard, Kendall, Union Sq Somerville, Western Ave/Lower Allston

I've been crayoning a Mass Ave BRT system for a while, and I hope to write about it at some point.

 

[JeffDowntown]

When calculating LMA transit demand, you need to include the LMA Shuttle system. 37 busses, it carries more than 7,000 daily riders to other T locations (mostly Red and Orange Lines).

 

[Teban54]

When calculating LMA transit demand, you need to include the LMA Shuttle system. 37 busses, it carries more than 7,000 daily riders to other T locations (mostly Red and Orange Lines).

That's a good point. I did find out from an earlier analysis (not published yet) that the GL D/E branch stations at LMA have higher alightings from downtown than boardings to downtown, meaning that more people take the Green Line to LMA than from LMA.

Do you have any sources and/or detailed analyses for the ridership of LMA shuttles?

Regardless, I don't think this changes the analysis significantly because:

• OL's ridership at Ruggles as a whole (not just limited to LMA shuttles) is still lower than Back Bay
  • Ruggles alone also only has 7,979 boardings, which means the 7,000 data that you cited probably includes both directions -- so 3,500 would be a more comparable figure
• People taking shuttles to JFK/UMass would only be influenced by the southern quadrant of the Urban Ring, whereas this discussion mostly concerns the western/SW quadrants
• AFAIK, shuttles to Harvard (the M2) are limited to Harvard ID holders
• Today's travel demand data for Cambridge-LMA, which includes non-transit trips, isn't particularly high
  • This is more of a "missed opportunity" situation, rather than a lack of latent demand; but still
• In my line of thoughts, the "Outer Ring" (Harvard-LMA) is always a mainstay; the question is what kind of additional service should be layered on top of it

 

[JeffDowntown]

That's a good point. I did find out from an earlier analysis (not published yet) that the GL D/E branch stations at LMA have higher alightings from downtown than boardings to downtown, meaning that more people take the Green Line to LMA than from LMA.

Do you have any sources and/or detailed analyses for the ridership of LMA shuttles?

Regardless, I don't think this changes the analysis significantly because:

• OL's ridership at Ruggles as a whole (not just limited to LMA shuttles) is still lower than Back Bay
  • Ruggles alone also only has 7,979 boardings, which means the 7,000 data that you cited probably includes both directions -- so 3,500 would be a more comparable figure
• People taking shuttles to JFK/UMass would only be influenced by the southern quadrant of the Urban Ring, whereas this discussion mostly concerns the western/SW quadrants
• AFAIK, shuttles to Harvard (the M2) are limited to Harvard ID holders
• Today's travel demand data for Cambridge-LMA, which includes non-transit trips, isn't particularly high
  • This is more of a "missed opportunity" situation, rather than a lack of latent demand; but still
• In my line of thoughts, the "Outer Ring" (Harvard-LMA) is always a mainstay; the question is what kind of additional service should be layered on top of it

Sorry, I am not aware of any detailed breakdown of the LMA usage. My understanding, though is all three main routes have significant usage.
(They restrict M2 to Harvard ID holders precisely because it is used heavily.)

 

[eber]

Sorry, I am not aware of any detailed breakdown of the LMA usage. My understanding, though is all three main routes have significant usage.
(They restrict M2 to Harvard ID holders precisely because it is used heavily.)

Here's an excerpt of Longwood Collective's data from around 2022 with pre/post pandemic ridership. There's probably better data somewhere else but this is a starting-point. (From "Longwood Collective Annual Report FY22")

It also has a blurb about specific routes, like the Fenway route being used by people who park / come from landsdowne CR stop for example.

 

[Riverside]

A small passing thought (not to overlook all of the really interesting analysis above): I wonder if a Kendall-Back Bay Line could be achieved via the Longfellow Bridge (or a new bridge right next to it) and then down the Esplanade to Beacon St. Then "Choose Your Own Adventure" how to actually get to "downtown" Back Bay from there. It's roundabout, but maybe that's not as bad as it seems.

 

[HenryAlan]

I've always thought something like this sketch made significantly more sense than an actual ring. What we need are lines serving cross-town routes and more outlying locations. The ring concept only partly addresses the need, giving more service to the idea that it is primarily a transfer route between already reachable areas. Your map seems far more useful for actual destination and origin pairings.

 

[Longfellow]

I like brown, but it is dumping more service to Lechmere, which is not dense and has almost no businesses. I almost wonder if it should jog north, but I don't know exactly where it would go. Maybe closer to Inman.

 

[TheRatmeister]

I like brown, but it is dumping more service to Lechmere, which is not dense and has almost no businesses. I almost wonder if it should jog north, but I don't know exactly where it would go. Maybe closer to Inman.

Honestly I think it should just join the Grand Junction.

 

[Teban54]

Lechmere, which is not dense and has almost no businesses.

I strongly disagree. Most of the screenshot below show the Cambridge Crossing developments just northeast of Lechmere station; a few others are apartment buildings to the west.

In comparison, here's the entire area from Inman Square (bottom) to Union Square Somerville (top):

The Cambridge Crossing website shows several companies setting up offices there. So while I'm not sure why the area has unimpressive figures in residents and jobs in the 2020 census or the latest LODES data, I still think there's strong potential from the developments there.

 

[Longfellow]

Almost all the buildings in that photo of Inman are dense lowrise multifamily, one of the densest housing types we have in Boston. I agree it would be great they built more than one apartment building at CX. The problem is that they built labs and a park... and the labs might not be fully leased. Red X shows parcels within a few blocks that don't have an appreciable number of people living at them. And this is borne out in what businesses see for demand--the only business lechmere ""square"" supports is a citizen's bank.

Yes it's cool that CX has a Tatte. I think that the development is flawed but great for Cambridge. But I don't really think it deserves it the way other neighborhoods do.

 

[TheRatmeister]

There is definitely development around Lechmere. It's just that said development is already very well served by the GL and OL, and would seemingly require 1 mile of extra subway as opposed to .5 miles of elevated if you want to both hit Cambridge Crossing, and have a transfer to the GL at Lechmere.

If you go via the GJ meanwhile, the transfer can be done fairly easily with a GL infill at Inner Belt.

 

[Teban54]

There is definitely development around Lechmere. It's just that said development is already very well served by the GL and OL, and would seemingly require 1 mile of extra subway as opposed to .5 miles of elevated if you want to both hit Cambridge Crossing, and have a transfer to the GL at Lechmere.
View attachment 63537

If you go via the GJ meanwhile, the transfer can be done fairly easily with a GL infill at Inner Belt.
View attachment 63539

A GLX infill at the flying junction that you labeled is likely infeasible for a few reasons:

• Any Green Line platform will need 225' of length for two Type 10 cars. The westbound Union Square ramp only has 160', and that includes the unbuilt ramp NE to GLMF.
• There seems to be a series of elevation changes on both "lines" (the Medford branch main line and the westbound Union Square ramp), although it's hard to see the exact elevation changes from Google Maps.

A much more realistic way to connect to the D/E branches west of Lechmere (with a Lowell Line transfer as a bonus) has already been discussed on this board several times before -- the "East Somerville alignment". This comment from @Riverside, and the chains of comments before/after, illustrate the alignment pretty well:

This has also been considered in real-world proposals before:

Nevertheless, in my sketches above, I still opted for Lechmere because:

• The East Somerville alignment is already taken by the Grand Junction Line (lime) in my map
• The development at Lechmere and its potential means that it can quite plausibly become a destination node on its own in the future, by the time any Urban Ring is seriously considered. This would increase the benefits of having a line running directly through it, instead of requiring another one-stop transfer -- much like Kendall.

 

[TheRatmeister]

Any Green Line platform will need 225' of length for two Type 10 cars. The westbound Union Square ramp only has 160', and that includes the unbuilt ramp NE to GLMF.

You need a slightly curved platform but this part is not a problem. I don't see anything in the design standards which would prohibit this.

There seems to be a series of elevation changes on both "lines" (the Medford branch main line and the westbound Union Square ramp), although it's hard to see the exact elevation changes from Google Maps.

As long as the grade doesn't exceed 1% it's fine. I can't tell if that's the case but it does not look particularly steep.

The Lowell Line station is a nice bonus but if you do a Charlestown/Chelsea branch with a station at Community College, you can also have CR interchange for all the Northside lines there.

 

[Teban54]

As long as the grade doesn't exceed 1% it's fine. I can't tell if that's the case but it does not look particularly steep.

According to the GLX Technical Proposal (document page 4-152, PDF page 12), looks like the grades are:

• 1.554% at the "No. 6 turnout", where outbound Union Sq branch splits from the Medford/Tufts "mainline"
• 1.001% at the "No. 10 turnout", where inbound Union Sq branch joins the Medford/Tufts "mainline"
• The figure doesn't show the precise figures for intermediate sections, but the track looks concave, so the grades are presumably between 1.001% and 1.554%

Given that the entire platform in your idea would lie between the two turnouts, they will likely face grades steeper than 1.001%, thus killing the proposal.

 

[TheRatmeister]

According to the GLX Technical Proposal (document page 4-152, PDF page 12), looks like the grades are:

• 1.554% at the "No. 6 turnout", where outbound Union Sq branch splits from the Medford/Tufts "mainline"
• 1.001% at the "No. 10 turnout", where inbound Union Sq branch joins the Medford/Tufts "mainline"
• The figure doesn't show the precise figures for intermediate sections, but the track looks concave, so the grades are presumably between 1.001% and 1.554%

Given that the entire platform in your idea would lie between the two turnouts, they will likely face grades steeper than 1.001%, thus killing the proposal.

View attachment 63550

From the same document, the Union Sq platform would be on a section with a gradient of approximately 0.5% so that side is totally fine. But you're right that the Medford side is steeper than 1%.

That being said, I would argue quite strongly that a viaduct needing modifications does not kill a proposal. There is no reason we must take existing infrastructure of any form, road or rail, as static and unchanging. Obviously it adds cost but I strongly suspect that the reduced length for the UR (and only needing one station rather than two) is more than enough to make up for that.

 

[Teban54]

That being said, I would argue quite strongly that a viaduct needing modifications does not kill a proposal. There is no reason we must take existing infrastructure of any form, road or rail, as static and unchanging. Obviously it adds cost but I strongly suspect that the reduced length for the UR (and only needing one station rather than two) is more than enough to make up for that.

I'll not elaborate too much here, but my verdict is that the "Brickbottom Junction modification" alignment is only cleanly optimal if you're dead set on routing the Urban Ring from Grand Junction to Community College, giving up Sullivan altogether. In this scenario, yes, it's the only viable option for a transfer to the GLX Medford branch.

But the moment you include Sullivan in consideration:

• The East Somerville - Sullivan alignment has almost negligible construction impacts (compared to a partial shutdown of the E for months if not years).
• It also has better walksheds (than a station surrounded by a literal rail interchange, the CRMF, and a highway).
• Their distances between Grand Junction and Sullivan are similar, with likely the same number of stops (the Brickbottom alignment will probably want a stop at the Twin City Plaza area anyway). The transfer walkways at East Somerville and a Twin City Plaza-ish infill will also be shorter than a Sullivan-Bound Grand Junction station.
• East Somerville does require a short tunnel between the D/E branches, but so will any Grand Junction route for crossing the Fitchburg ROW to Sullivan.
• (The main disadvantage of the East Somerville alignment is the number of curves.)

I think Sullivan is a better transfer point than Community College for many reasons. Much better bus transfers; much better transfer geometry from northside Orange Line; likely better redevelopment potential (Sullivan's location is more advantageous); and the ability to continue north to Everett.

 

[TheRatmeister]

The East Somerville - Sullivan alignment has almost negligible construction impacts (compared to a partial shutdown of the E for months if not years).

I mean, I'd think such a modification could be done by just raising the track and adjusting the height of the wires rather than actually modifying the concrete viaduct. The actual height adjustment we're talking about here is a little over 1 foot at its maximum. Assuming that can be done, that's more like weekend work.

It also has better walksheds (than a station surrounded by a literal rail interchange, the CRMF, and a highway).

Maybe a little? But the large adjacent Morgan Ave parcel is being redeveloped and there's a significant amount of development coming up along Rt 28.

I think Sullivan is a better transfer point than Community College for many reasons. Much better bus transfers; much better transfer geometry from northside Orange Line; likely better redevelopment potential (Sullivan's location is more advantageous); and the ability to continue north to Everett.

I'd say it's pros and cons. Here's a (probably incomplete, feel free to add more) list for both stations:

Pros	Cons
Sullivan	Shorter bus routes to Everett, Somerville, and Medford Easy surface level OL transfer, could possibly even be redesigned into a cross platform transfer Close to residential development in Somerville plus plenty of open space for redevelopment Can continue a new line to Everett	Being right next to 93 really limits development potential With heavy sound deadening it's probably okay for commercial but I doubt we'll see any residential on that site anytime soon. Misses interchange with Lowell and Fitchburg Lines
Community College (Should probably be renamed to something else in this scenario)	Interchange with all Northside CR lines Adjacent to existing and ongoing development at Cambridge Crossing Potential for new adjacent development in current nearby parking lots Can continue a new line to Chelsea	Also right next to 93 so future development on those parking lots has the same problem as at Sullivan Same caveats about commercial being more feasible than residential. OL transfer is not great unless the UR station is underground Terrible bus terminal, Maybe by reusing the truck pad this could be fixed? Any buses could be extended along Rutherford Ave, the proposed median running lanes there would make that trip very fast. Misses the main cross-Camberville route (109) Hopefully the 101 can alleviate this somewhat but it's at best a highly imperfect substitute, and really serves a different purpose.

I'm really not sure which way to go on that. It's one big reason why I have both in my UR on my fantasy map. I think Community College has strong potential as a 'megahub' between the OL, UR, CR, and some buses, while Sullivan is likely to continue to be a powerhouse for bus transfers. They both lend themselves better to different continuations, which is the other major reason they both feature in my fantasy maps. So maybe trying to pick one is just a poor idea in the first place.

 

[samsongam]

I mean, I'd think such a modification could be done by just raising the track and adjusting the height of the wires rather than actually modifying the concrete viaduct. The actual height adjustment we're talking about here is a little over 1 foot at its maximum. Assuming that can be done, that's more like weekend work.

Maybe a little? But the large adjacent Morgan Ave parcel is being redeveloped and there's a significant amount of development coming up along Rt 28.

I'd say it's pros and cons. Here's a (probably incomplete, feel free to add more) list for both stations:

Pros	Cons
Sullivan	Shorter bus routes to Everett, Somerville, and Medford Easy surface level OL transfer, could possibly even be redesigned into a cross platform transfer Close to residential development in Somerville plus plenty of open space for redevelopment Can continue a new line to Everett	Being right next to 93 really limits development potential With heavy sound deadening it's probably okay for commercial but I doubt we'll see any residential on that site anytime soon. Misses interchange with Lowell and Fitchburg Lines
Community College (Should probably be renamed to something else in this scenario)	Interchange with all Northside CR lines Adjacent to existing and ongoing development at Cambridge Crossing Potential for new adjacent development in current nearby parking lots Can continue a new line to Chelsea	Also right next to 93 so future development on those parking lots has the same problem as at Sullivan Same caveats about commercial being more feasible than residential. OL transfer is not great unless the UR station is underground Terrible bus terminal, Maybe by reusing the truck pad this could be fixed? Any buses could be extended along Rutherford Ave, the proposed median running lanes there would make that trip very fast. Misses the main cross-Camberville route (109) Hopefully the 101 can alleviate this somewhat but it's at best a highly imperfect substitute, and really serves a different purpose.

I'm really not sure which way to go on that. It's one big reason why I have both in my UR on my fantasy map. I think Community College has strong potential as a 'megahub' between the OL, UR, CR, and some buses, while Sullivan is likely to continue to be a powerhouse for bus transfers. They both lend themselves better to different continuations, which is the other major reason they both feature in my fantasy maps. So maybe trying to pick one is just a poor idea in the first place.

My three main issues for me with the idea of a Community College mega station are

1. It's not all that far from North Station or enough of a center to warrant a CR stop to me. As you mentioned, it's flanked by a highway, which limits its development potential so it's probably not going to be much of a center. Placing a major transfer point so close to North Station feels redundant to me.

2. There are a lot of tracks through here connecting Fitchburg, Lowell, the Maintenance Facility, and the yard. Presumably, you'd have to simplify some of the track layout. How much flexibility are you giving up by building platforms right at the end (maybe beginning?) of all the interchanges?

3. If we see NSRL as a long term goal, an underground stop here would be incredibly expensive/ impossible, whereas infills at Sullivan and East Somerville (maybe somewhere near Union Sq. too?) fits in perfectly fine with that future reality and allows for transfers.

 

[Teban54]

Community College CR station

IF a mega station here is feasible, I can see the great value that it would add.

• Proximity to Cambridge Crossing is the biggest asset here, as the CR ROW is even closer to some offices than Lechmere is. Cambridge Crossing is no Kendall and no Back Bay at the moment, but it still has potential as a decent TOD, before even considering possible developments north/east of I-93. The CR ROW is also closer to the developments than the Orange Line is, offsetting walkability disadvantages that affect the OL station.
• Another less trivial benefit is simplicity of a single CR station. Instead of the three northside CR lines each having its own transfer stop with the Urban Ring, this is the only alignment that allows a centralized transfer. It's much easier for operations and for riders to understand.

But in general, I remain skeptical of the idea -- precisely because of cost and feasibility.

In an NSRL world, Community College would not only be underground, but also along the northern portals:

The NSRL slides mention a maximum allowable grade of 3%. TL;DR: I played around with the numbers, and the original portal locations above may still work -- even with 800' level platforms, they don't seem to have steeper grades than the Back Bay - South Station grades in the same presentation. But given that the Back Bay portal in the slides has a grade of 3.65%, something seems fishy to begin with. (Perhaps I didn't subtract the depth of the tunnel itself?)

Still, this is already a complex area between the egress, branches, possible flying junctions for the branches, etc. Not only do additional engineering concerns have potential to worsen feasibility, but the added cost -- especially for another underground CR station (even though this one is much more feasible for C&C than the downtown stations) -- raises the question of whether it can win in a cost-benefit analysis against 3 surface CR stations (Twin City Plaza, East Somerville, Sullivan Sq).


If we're living without Community College CR

Without a CR mega station here, I argue that the value of bringing the Urban Ring to Community College drops significantly. From @TheRatmeister's comparison table, the major advantages unique to Community College are CR and Cambridge Crossing.

Granted, I've been of the belief that bringing the Urban Ring to Cambridge Crossing. But there's a reason why I always preferred doing it via Lechmere and not Community College:

• The "CC vs. Sullivan" decision has too much ripple effects on where the line would go further north/east. You're dealing with fundamentally different networks at that point:
  • Sullivan lets you continue to Encore and Everett easily, and also allows for the (more unconventional and costly) idea of a "cross-Charlestown subway" to Navy Yard, East Boston and Logan Airport.
  • While Community College still allows the Eastie/Airport connection, it effectively locks you into Chelsea for any radials.
  • For reasons described below, I think Chelsea is inherently less suitable for Urban Ring than Everett is.
• In contrast, the "Lechmere vs. Brickbottom vs. East Somerville" decision only affects local alignments. Any of the three can still get you to Sullivan and points north, along the more developed proposals. Even getting to Community College is feasible for all three (albeit ES-CC is a stretch).

While a Lechmere connection is a simpler question of "whether serving Lechmere is worth the cost", CC vs. Sullivan goes way beyond Cambridge Crossing and involves evaluating two network philosophies. That alone requires more careful consideration; not to mention that CC's effects on network topology trend towards a direction that I personally disagree with.

Keep in mind, the East Somerville alignment isn't hopeless with the Fitchburg and Lowell transfers, which eliminates a major con for Sullivan:

• A Lowell Line infill at East Somerville is easy peasy.
• The Fitchburg Line can probably afford an infill at Twin City Plaza (the McGrath / Squires Bridge vicinity), as long as it's offset from the GLX infill that would also be necessary here. It likely requires moving the support columns of the Squires Bridge (if not a full rebuild), but that's not nearly as complex as Brickbottom modifications.

I'll also briefly mention that Sullivan isn't running out of space for redevelopments -- the triangular parking lot between Main St and Cambridge St has roughly the same area as the CC parking lot between New Rutherford Ave and I-93. With ongoing plans to reconfigure Sullivan Sq's street grid, it has strong potential to be made more pedestrian-friendly and attract further developments. And if some industrial parcels there can be repurposed, it gives you much more space than CC.


Chelsea vs. Everett: The radial end of a "tangential" Urban Ring line

Most of this had been explained in my Kendall-Back Bay post, specifically the "Why radial line to Everett?" dropdown box:

A few additional points:

• Don't forget, a Tobin Bridge line can still serve as a radial line to both Everett and Chelsea, just with a more zigzag route.
• A Chelsea-downtown route doesn't necessarily need a new downtown subway (although it would be nice to have). The most realistic solution IMO is actually a Green Line branch from North Station. (Note that the Tobin Bridge is equally far from North Station vs. Community College.)