This is the map I've been looking at. Individual census blocks, within 10km of Park Street, colored by Housing Unit density. You can click on each block for more details.
Blue Line heavy rail along that route to Needham is a way better proposal than extending the D that way or the Orange Line from the east. It would give the speed of the Orange Line but serve a corridor with many more destinations of interest to Needhamites (you'd struggle to find many people moving between Needham and Roslindale as opposed to Newton).
No, I disagree. Needham-Newton Traffic can be served just fine by a light rail service, you won't struggle at all to fill an Orange Line train with Needhamites moving to Back Bay or Ruggles, and if you've already dug up half of Storrow to get the Blue that far, there's no reason not to send it to Oak Square instead (with the eventual goal of restoring transit to Watertown).
Blue-eats-D is a terrible idea.
My only other complaint with that map is that the Mass Ave. Subway / Line 10 splits off of the Red Line at Andrew instead of JFK/UMass, but that's comparatively minor.
The Needham Line corridor cuts across a rather large swath of protected and uninhabitable land that makes it much less appealing for upgrading to rapid transit, especially considering the D branch would traverse a denser area with a lot of potential around 128. The 1945 MTA plan even had a heavy rail Riverside Line branching to Needham and the Orange Line continuing past West Roxbury to Dedham. Obviously the West Roxbury-Dedham corridor has been compromised, but the extension to West Roxbury would still be wildly successful.
The Blue-D combination just seems so natural. I'd guess that the two lines, meaning D from Riverside to Government Center and the entire Blue, see similar passenger numbers, which would make it a very used line across its whole route. The D may actually have the leg up now, but the Blue Line has massive potential for substantial increases with an extension to Lynn.
The point there would be to maximize the number of single transfers from the three lines that converge. Otherwise, everyone would have to make a double transfer to get from Line 10 to Line 12 (changing first at JFK/UMass and then at Andrew, or vice-versa)
The Blue-D combination just seems so natural. I'd guess that the two lines, meaning D from Riverside to Government Center and the entire Blue, see similar passenger numbers, which would make it a very used line across its whole route. The D may actually have the leg up now, but the Blue Line has massive potential for substantial increases with an extension to Lynn.
As a former resident of Newton who grew up minutes from the D and used it often, it would be awful for Newton (and worse for Needham) to convert that line to HRT. Newton folks tend to use the Green Line to get between parts of Newton more than to get to Boston - I know of very few people who regularly went beyond Chestnut Hill - and for that purpose LRT as it's currently built works fine. This is even more important when talking about the extension to Needham, since that line isn't grade separated and would be pretty well embedded in village centers. Even where HRT exists at grade (I'm thinking about Chicago here), it tends to be ugly and uninviting, with heavy fencing of the ROW due to the third-rail safety issue. LRT is much less intimidating.
People in Needham won't be using this service to get to Boston since they'll have either truncated CR or Orange Line for that, making fewer stops at higher speeds. Similarly, folks from Riverside and points west won't (and don't) go all the way into Boston that way much, since under a full build-out there would be DMU or HRT along the Pike.
As I've said before, the D and Needham lines are primarily intra-suburban lines with redundant faster spokes to Downtown. That's about as clear-cut a context for LRT as you can get.
What about keeping the D as light rail, four-tracking from Kenmore to Park Street what isn't four-tracked already, cutting the D back to Park Street, and converting one of the other Green Line branches to Heavy Rail? You'd get two HRT tracks and two LRT tracks from Kenmore to Park, and cross-platform transfers from heavy rail to light rail. It'd be a bit of an engineering challenge and probably require an elevated ROW, but hey, this is Crazy Pitches.
Would the B branch be better served as Heavy Rail?
What about keeping the D as light rail, four-tracking from Kenmore to Park Street what isn't four-tracked already, cutting the D back to Park Street, and converting one of the other Green Line branches to Heavy Rail? You'd get two HRT tracks and two LRT tracks from Kenmore to Park, and cross-platform transfers from heavy rail to light rail. It'd be a bit of an engineering challenge and probably require an elevated ROW, but hey, this is Crazy Pitches.
Would the B branch be better served as Heavy Rail?
A "bit" of an engineering challenge? Try a humongous engineering challenge. That's Back Bay landfill. All the buildings are sitting on wood stilts. You've got hundreds of pumps balancing the water table. There is no freaking way the Central Subway is getting touched between Mass Ave. and Boylston. They could build it in the first place because the landfill was new and there were tons of open lots on Boylston. The filled-in density wouldn't work. At least not on old, unreinforced infrastructure like that. Under Boylston is a lot different than, say, the Pru complex where the landfill was compressed flat to support the weight of the ex-train yards that moved in the second the filling was finished. I mean, the Copley elevator project started causing the church outside to develop masonry cracks. That's how fragile the underground dependencies are under those streets.
If you're going to add extra track capacity to Kenmore...the Riverbank Subway is it. Or Huntington Ave. BERy had both of those proposals going for a reason. The diggable places in town are under the B and E reservations, under the NEC, in the cleared Big Dig fill (under, around, etc.) and on the Pike frontage roads. For the same reason BRT under Chinatown was a batshit insane idea, quadding the Central Subway ain't gonna work without costing billions in overruns and royally, royally screwing up the surface for years on end. For something a parallel route offset several blocks would get them sooner, at half the cost, with a fraction of the frayed nerves.
Here's the most practical way of going, in my opinion - I think this will raise some ire, but I model this after real multimodality like you can see in Toronto.
GLX, Central Subway and D Line - complete heavy rail conversion
B and C become street-running light rail OVER the central subway, primarily through the Back Bay in one-way pairs along Newbury and Boylston using one current parking lane of each street. Kenmore's overbuilt bus shelter can now be used for these light rail lines, which, downtown, loop around the Commons to connect at Park Street.
E tunnel from Prudential gets continued cut-and-cover along Stuart Street, rises to a surface median where Stuart/Kneeland widens, and continues up Atlantic into the SL tunnel to South Station and out to the Seaport. The disused Tremont Street Tunnel can be repurposed - its northernmost section as a pedestrian concourse between the Boylston Street heavy rail station and a light rail Stuart/Charles street station; the section south of Stuart Street as an F line light rail branch from the E mainline to Dudley.
Whatcha think? Ready to bring back the streetcars?
As a former resident of Newton who grew up minutes from the D and used it often, it would be awful for Newton (and worse for Needham) to convert that line to HRT. Newton folks tend to use the Green Line to get between parts of Newton more than to get to Boston - I know of very few people who regularly went beyond Chestnut Hill - and for that purpose LRT as it's currently built works fine.
Personally, I'd much rather bring back the El, but I am too young to remember the old Els, so perhaps my judgment is flawed. Alas...
As it stands, I don't know if I'm ready to get on board with more surface-running.
Here's the most practical way of going, in my opinion - I think this will raise some ire, but I model this after real multimodality like you can see in Toronto.
GLX, Central Subway and D Line - complete heavy rail conversion
B and C become street-running light rail OVER the central subway, primarily through the Back Bay in one-way pairs along Newbury and Boylston using one current parking lane of each street. Kenmore's overbuilt bus shelter can now be used for these light rail lines, which, downtown, loop around the Commons to connect at Park Street.
E tunnel from Prudential gets continued cut-and-cover along Stuart Street, rises to a surface median where Stuart/Kneeland widens, and continues up Atlantic into the SL tunnel to South Station and out to the Seaport. The disused Tremont Street Tunnel can be repurposed - its northernmost section as a pedestrian concourse between the Boylston Street heavy rail station and a light rail Stuart/Charles street station; the section south of Stuart Street as an F line light rail branch from the E mainline to Dudley.
As somebody who has lived in Newton, within a mile of the D, for the past 21 years, I disagree. I found this used to be the case in the old price structuring, but that all changed in 2007. When it became the same price no matter where you were leaving from/going to, and the free rides going outbound ended, people adapted. Now, I find the majority of trips people I know take are going to Resevoir or beyond, while 5+ years ago it was within Newton.