Green Line Reconfiguration

[F-Line to Dudley]

I never really got the purpose of feeding a Harvard Branch via GJ. If you're getting on a ring GL train at North Station and you want to get to Harvard, wouldn't you just get off at a Kendall transfer (yeah, yeah, it's not behind fare gates... ) and go two stops on Red rather than staying on Green for 6-8 mores stops?

The Harvard Branch always made more sense to me as being fed out of the central subway, or as part of the urban ring boomerang B inbound-D outbound-E inbound concept.

Well, yeah. But the way that one is situated the junction would be on the surface on the grassy knoll and could be fed any which way. Just like you could run Boston College service off the D via Reservoir and Chestnut Hill Ave. if you really wanted to. Doesn't mean there's a compelling reason to run it off the GJ, but you could if you wanted to. It would be set up right out of the box to do that if the hillside portal exists at all, the GJ LRT line exists at all, and the Harvard branch exists at all. The tunnel off the B subway popping out on the hillside and the tunnel popping out at BU West, however, just don't have the favorable angles to do similar either/or routings.

 

[vanshnookenraggen]

The Harvard Branch always made more sense to me as being fed out of the central subway, or as part of the urban ring boomerang B-inbound to D-outbound to E-inbound concept.

This is the beauty of tying the Urban Ring into the expanded Green Line. If you design it in phases then each phase will improve Green Line service and by the time it is all built out you have a full Urban Ring LRV and you already know what service patters will be best by seeing the ridership of each phase. Alon seems to be against this, I guess he prefers the all-or-nothing route but since it's so hard and expensive to build subways here I feel like a phased construction plan is the only way to kill two birds with one stone.

More generally, though, there are so major issues with the Urban Ring that can't be solved with more subways or more buses. It goes back to the way Boston grew with the hub-and-spoke design. Using the GJ looks good on paper until, as F-Line and many other have pointed out, you look at how the area surrounding it was developed.

The Everett/Chelsea/Airport corridor is also a challenge and one that I feel expanded Silver Line service is best for.

This leaves the major CBDs outside of downtown/Back Bay to be connected somehow and there are no easy ways to do this. Again, it seems the best way would be to upgrade the Green Line is phases that address the needs of each area and build out in such a way that a circuitous service could be implemented once each project is completed.

 

[F-Line to Dudley]

This is the beauty of tying the Urban Ring into the expanded Green Line. If you design it in phases then each phase will improve Green Line service and by the time it is all built out you have a full Urban Ring LRV and you already know what service patters will be best by seeing the ridership of each phase. Alon seems to be against this, I guess he prefers the all-or-nothing route but since it's so hard and expensive to build subways here I feel like a phased construction plan is the only way to kill two birds with one stone.

More generally, though, there are so major issues with the Urban Ring that can't be solved with more subways or more buses. It goes back to the way Boston grew with the hub-and-spoke design. Using the GJ looks good on paper until, as F-Line and many other have pointed out, you look at how the area surrounding it was developed.

The Everett/Chelsea/Airport corridor is also a challenge and one that I feel expanded Silver Line service is best for.

This leaves the major CBDs outside of downtown/Back Bay to be connected somehow and there are no easy ways to do this. Again, it seems the best way would be to upgrade the Green Line is phases that address the needs of each area and build out in such a way that a circuitous service could be implemented once each project is completed.

I threw this together more as an example than thorough plan.

Urban Ring/Green Line Phased Plan

Phase 1: Green Line Harvard Branch off Comm Ave.
Phase 2: Huntington Ave extension (using Francis St alignment to connect with Riverside line)
Phase 3: Comm Ave subway extension past Packards Corner (I have a portal for the B branch after Packards Corner but the subway could also head west under Brighton Ave to Allston and beyond)
Phase 4: Connecting each line via Urban Ring.
- The alignment with the least additional tunneling would go under Blanford St and loop back to connect with the Riverside line.
- After Longwood the UR would connect with the Huntington Ave Ext until Ruggles where it would enter a new tunnel to Melnea Cass Blvd.
- At Melnea Cass Blvd the line would run either elevated or at grade (or a combination) to Mass Ave where it would run elevated around the Mass Ave Connector/I93 interchange and terminate at Andrew Sq Red Line.

An alignment such as this is, IMO, smarter than one more focused on connecting the Orange Line to Kendall Sq via the GJ. Besides hitting more of the major employment centers around Boston it also acts as a bypass for the Red Line. I've seen many a plan on here with a Red Line branch under Mass Ave but that will always be a recipe for disaster given Red Line commuter patterns. This UR alignment sticks close to Mass Ave as possible while using as much existing ROW as possible, upgrading that ROW, and siphoning off Red Line riders that would normally transfer at Park St.

I'm not arguing this is the best alignment but rather an example of how the phased plan can be accomplished. In regards to terminating at Andrew Sq I feel like this is a better compromise than continuing to JFK/UMass as Andrew is a larger bus transfer hub, is closer to the residential section of Southie, and is close to the South Bay Center which may be redeveloped and even if not is a large shopping destination.

For purposes of load-balancing Grand Junction LRT really helps. A Central Subway flanked by the Huntington tunnel to the south and the GJ to the north. That's what allows you to throw the service patterns in a blender. Including multiple types of circuit service. The GJ, not requiring tunneling costs other than the much easier cut-and-cover job under the B reservation to BU Bridge, is the easier place to start. You probably do have ample capacity by this point to do the Chelsea leg off the 4-way Brickbottom Jct. with the flanks established.

As for the Harvard spur...you have to fork it at BU Bridge. The streets up near Packards are way, way too narrow for that. And you have a pre-existing interface to get on-trajectory to Harvard at the point where the GJ runs along the Pike. For this reason, if you're going to bury the B for the 'boomerang' loop at Kenmore onto the D (since the cross-Brookline tunnel actually proposed is a nonstarter), BU Bridge and the line split at "BU Central Under" is the only tunneling that really matters. Once you spit back to the surface at Pleasant St. it's on the other side of the worst of the B traffic clogs. You would of course be able to continue the tunnel if there was ever reason to plow into Allston. I just don't see that ever rising to the level of urgency.



May have been lost in old threads, but you DON'T have to build the N-S Link in order to free up the Grand Junction for a flip to LRT. It takes this:

-- A full-service southside commuter rail maint facility so the equipment swaps to Boston Engine Terminal no longer have to be daily. At the very least something that can maintain 100% of the southside coach fleet, any electric vehicles, DMU's, and so on. 92-day diesel locomotive inspections, heavy repair of cars that are going to be out-of-service for awhile...that's still fine to send to BET.

-- Enough fleet expansion that south and north are self-sustaining without need for constant trading of equipment. i.e. If stuff needs a load-balancing, make that north-south trip once every 3 weeks instead of once a day.

-- Upgrades of the Pan Am Worcester Branch to minimum 40 MPH speeds. It takes 5 hours right now to do a north-south swap by that route. Doubt we're going to see that until somebody buys out Pan Am (east/non-Norfolk Southern side of the system). If the moves only have to happen once a week instead of once a day, that ends up cost-neutral for ops on fuel consumption, number of crews who have to be qualified on the connecting route, etc.

-- Cut a maint deal with Amtrak to maintain the Downeaster trainsets at BET, since instead of daily swaps via the GJ to/from their facility at Southampton Yard they'll likewise need to limit their equipment shuffles to once a week on an MBTA piggyback to keep it cost-neutral.


That's probably a few hundred mil in eat-your-peas stuff, most of it tied up in the southside maint facility and buffing out the rolling stock reserves, but long-term it's kind of needed regardless. Do that and an LRT Ring segment on the GJ is de-coupled from any dependency on the N-S Link advancing on similar schedule. They are functionally independent projects if you take the much smaller-potatoes steps above to backstop the commuter rail fleet needs.

 

[George_Apley]

That's probably a few hundred mil in eat-your-peas stuff, most of it tied up in the southside maint facility and buffing out the rolling stock reserves, but long-term it's kind of needed regardless.

I was thinking that too. Won't BET need some relief eventually when fleet gets expanded? Another maintenance facility will probably be needed even if the NSRL gets done.

 

[asap_mozart]

There's whatever's left of the medford branch?

 

[F-Line to Dudley]

There's whatever's left of the medford branch?

All 2500 ft. of it. It's 1000% obliterated past the cold storage warehouse on Middlesex Ave. You can't even trace the ROW from there so many backyard swimming pools have been built on it in the 40 years since it was chopped back that far. GLX gets physically closer to Medford Square than anything spurrable off Orange is capable of getting.


That's a future walking path from the west side of Fellsway and a footbridge over the lone surface track for reaching Rivers Edge Dr. whenever that track gets abandoned. Which is a plus mobility gain for that neighborhood that has poor walking access to the waterfront and Wellington station. But that's the only prospect that spur is good for. I'm not sure why people keep imagining a transit branchline on that thing. It's all gone.

 

[George_Apley]

All 2500 ft. of it. It's 1000% obliterated past the cold storage warehouse on Middlesex Ave. You can't even trace the ROW from there so many backyard swimming pools have been built on it in the 40 years since it was chopped back that far. GLX gets physically closer to Medford Square than anything spurrable off Orange is capable of getting.


That's a future walking path from the west side of Fellsway and a footbridge over the lone surface track for reaching Rivers Edge Dr. whenever that track gets abandoned. Which is a plus mobility gain for that neighborhood that has poor walking access to the waterfront and Wellington station. But that's the only prospect that spur is good for. I'm not sure why people keep imagining a transit branchline on that thing. It's all gone.

People imagine it going underground to Medford Square. I've fancied that in the past... but I don't think it gets remotely enough bang for the mountains of bucks it would require.

 

[vanshnookenraggen]

Once the GLX opens bus lines will be reconfigured and Medford Center will be fine with that. When I was still in Arlington I had a friend of mine live off Main and George St in Medford so I got used to taking the bus from Harvard or Davis. That is a hike but not terrible (since we worked in Harvard Sq). Once the GLX opens the bus to Medford Center becomes quick enough to deal with any issues.

I don't really remember the plans for the Rt 16 station but I feel like that is in a better position for a bus terminal than College Ave. Right now you've got the 80, 94, and 96 which run through the College Ave/Boston Ave corridor. I can see these being reworked; the 96 will probably stay the same given the area it covers but the 80 could be rerouted to go from Arlington Center>College Ave >Medford Center>Malden Center or Wellington.

 

[vanshnookenraggen]

For purposes of load-balancing Grand Junction LRT really helps. A Central Subway flanked by the Huntington tunnel to the south and the GJ to the north. That's what allows you to throw the service patterns in a blender. Including multiple types of circuit service. The GJ, not requiring tunneling costs other than the much easier cut-and-cover job under the B reservation to BU Bridge, is the easier place to start. You probably do have ample capacity by this point to do the Chelsea leg off the 4-way Brickbottom Jct. with the flanks established.

As for the Harvard spur...you have to fork it at BU Bridge. The streets up near Packards are way, way too narrow for that. And you have a pre-existing interface to get on-trajectory to Harvard at the point where the GJ runs along the Pike. For this reason, if you're going to bury the B for the 'boomerang' loop at Kenmore onto the D (since the cross-Brookline tunnel actually proposed is a nonstarter), BU Bridge and the line split at "BU Central Under" is the only tunneling that really matters. Once you spit back to the surface at Pleasant St. it's on the other side of the worst of the B traffic clogs. You would of course be able to continue the tunnel if there was ever reason to plow into Allston. I just don't see that ever rising to the level of urgency.

UPDATED MAP

Urban Ring/Green Line Phased Plan

Phase 1: Green Line Comm Ave extension past BU Bridge with portal at BU West. BU Central station built bi-level for future UR connection.
Phase 2: Huntington Ave extension (using Francis St alignment to connect with Riverside line)
Phase 3: Connecting each line via Urban Ring.
- The alignment with the least additional tunneling would go under Blanford St and loop back to connect with the Riverside line.
- After Longwood the UR would connect with the Huntington Ave Ext until Ruggles where it would enter a new tunnel to Melnea Cass Blvd.
- At Melnea Cass Blvd the line would run either elevated or at grade (or a combination) to Mass Ave where it would run elevated around the Mass Ave Connector/I93 interchange and terminate at Andrew Sq Red Line.
Phase 4: Grand Junction Line built from BU Bridge to Sullivan Sq.

An alignment such as this is, IMO, smarter than one more focused on connecting the Orange Line to Kendall Sq via the GJ. Besides hitting more of the major employment centers around Boston it also acts as a bypass for the Red Line. I've seen many a plan on here with a Red Line branch under Mass Ave but that will always be a recipe for disaster given Red Line commuter patterns. This UR alignment sticks close to Mass Ave as possible while using as much existing ROW as possible, upgrading that ROW, and siphoning off Red Line riders that would normally transfer at Park St.

I'm not arguing this is the best alignment but rather an example of how the phased plan can be accomplished. In regards to terminating at Andrew Sq I feel like this is a better compromise than continuing to JFK/UMass as Andrew is a larger bus transfer hub, is closer to the residential section of Southie, and is close to the South Bay Center which may be redeveloped and even if not is a large shopping destination.

Edit: This map working yet?

 

[West]

UPDATED MAP

Urban Ring/Green Line Phased Plan

Edit: This map working yet?

yes, it is for me this morning

 

[Downburst]

I see it! Looks great, Van.

My only question is about the D/E connector at Brigham Circle- would that be an at-grade junction? If so, would it be subject to the same delays as Copley Junction, or would delays be reasonably fewer, as the junction would serve two branches instead of four?

 

[citylover94]

Would it work/ be possible to do it as a grade seperated junction so there isn't an issue with that or to do it as a two level subway with the urban ring and the E not sharing track?

 

[F-Line to Dudley]

I see it! Looks great, Van.

My only question is about the D/E connector at Brigham Circle- would that be an at-grade junction? If so, would it be subject to the same delays as Copley Junction, or would delays be reasonably fewer, as the junction would serve two branches instead of four?

It would work this way:

1. Cut and cover from Northeastern portal to Brigham. 1 mile of tunneling under the existing reservation footprint. Pretty straightforward.

2. Continue the cut-and-cover to Riverway under-street. About ~2000 ft. of more invasive tunneling. Significant surface impacts because of utility relocation, but as a 4-lane street with no curbside-abutting buildings exceeding 4 stories there wouldn't be any structural impacts. And the Mission Hill area is away from the landfill mush. As long as they can stage the surgery to be over with briskly enough it's pain you can swallow for the relatively self-contained project area.

3. Get on-alignment under the Riverway intersection to Brookline Village. This is where it gets fuzzy because there's no way of knowing +/- 500 ft. of the most realistic trajectory until the engineers study it. You sort of have to draw a rectangle between Riverway and the square, call that the "project limits", then assume there is some preferred alternative that'll emerge through EIS and engineering that accomplishes the major coals. But can't really make assumptions what that'll look like as lines on a map other than ballparking it and focusing on desired configuration.

4. Station and surface interface. Dependent on same assumptions/non-assumptions as #3.


This is my MS Paint concept of Brookline Village superstation:

Multi-directional access:
-- regular Riverside via Central Subway/Kenmore service
-- Riverside via Huntington Subway
-- Urban Ring-via-Kenmore to Huntington. (Note: involve the Harvard spur and this is your "save the 66" congestion solution for the heaviest Harvard-Longwood ridership on that bus, even though it's not a drop-in replacement for the full 66 routing and all destinations therein.)
-- Central Subway to Huntington Subway 'circuit' service
-- Huntington Subway to Arborway/Forest Hills. Streetcar tracks forking here and backtracking the 2 blocks to South Huntington. Assume that even though traffic's far less than awesome here on these 2 blocks, expunging that much Huntington Ave. surface mileage for the streetcar makes the shorter route to FH overall work way better than it did in its previous life.
-- Central Subway/Kenmore to Arborway/Forest Hills
-- Urban Ring-via-Kenmore to Arborway/Forest Hills

Air rights cover-over gets re-developed, and "super-platforms" under the overhang with different loading berths for different services spans the area where the tunnel splits and portals from very shallow depth. I suppose you could stretch the Kenmore-pointing junction further east to allow for some extra 4-track running room and an extra platform if you're concerned about congestion (less of a concern on the Riverside/Arborway-pointing junction) if the width is available under the air rights. I won't make that assumption on this MS Paint crayon sketch (because I flat-out forgot until after I'd already finished the sketch!), but that is a viable possibility. Let's say Riverside-via-Kenmore and Arborway-via-Kenmore takes the midsection of the platform where the tunnel is making its underground split, and Riverside-via-Huntington and Arborway-via-Huntington berths on the westerly edge. That's probably cleanest for keeping those lower-frequency branches out of each other's way.

The D/Huntington tunnel merges in both directions are fluid grade-separated junctions where D tracks spread around the center portals. Arborway split and the underground split are the only grade-separated junctions. Arborway, of course, low-volume, and the mixed patterns with UR or Central Subway-Huntington Subway circuit service well outslug the D-to-E frequencies so conflict potential is very limited.

Since this becomes a way bigger bus transfer point, the revamped air rights has a busway connection from the Kent/Station St. intersection to Pearl St. And the air rights itself gets rebuilt with potential for tall buildings on top instead of that lone parking deck that's such sub-optimal land use.

As noted, the whole works may have to shift around within this 1-block project area depending on what the engineers say. So this is subject to interpretation. Goal is just to get something resembling this as a super-node for diverging routes and have your ducks in a row on what you're willing to tweak or compromise away should the engineer-recommended routing come out less favorable (because none of us know enough yet to treat this layout at locked within +/- 500 ft.).

 

[vanshnookenraggen]

I see that being very difficult and expensive to build. I don't think the space required is there unless you want to eminent domain a few of those apartment buildings. That's why I prefer an alignment closer to Longwood; more room to work with as all you are digging though is empty park land.

Downburst: The way I imagine it is that the junction is bi-level with one direction on each level. It would be easier that way than a flying junction. The whole point is to eliminate as many at grade junctions as possible.

 

[George_Apley]

^ But what about digging down Francis? A lot of potential mitigation issues with the hospitals...

 

[F-Line to Dudley]

I see that being very difficult and expensive to build. I don't think the space required is there unless you want to eminent domain a few of those apartment buildings. That's why I prefer an alignment closer to Longwood; more room to work with as all you are digging though is empty park land.

Downburst: The way I imagine it is that the junction is bi-level with one direction on each level. It would be easier that way than a flying junction. The whole point is to eliminate as many at grade junctions as possible.

Longwood is even tougher. Longwood Ave.'s a 2-lane street (so is Francis), very tall NU and hospital buildings right up to curbside its entire length. Then crossing the Muddy River at its widest point. Then bang-bang interfacing with the D right next to the river and walking path. Going along Fenway via Louis Prang St. has similar issues of waterproofing around the Fens and a river crossing right where it interfaces with the D.

All that stupidity was part of the south half of the Phase III study's cross-Brookline tunnel recycling the old I-695 tunnel alignment. It's deader than dead for exactly the same reasons the 695 schematics weren't worth the paper they were printed on.


You don't have an easy interface, but BV has the street width for cut-and-cover tunneling and trajectory off Huntington. And the fewest by far wetlands to square. If you have to raze any buildings the Pearl block w/ that New England Institute of Art eyesore and the hospital office buildings are the most disposable/rebuildable of any. The apartment buildings flanking the air rights garage shouldn't be an issue, though. They're separated by 125 ft. on either side of the ROW with just that flimsy deck over the tracks between them, and set back ~30-40 ft. from curbside.

It's not without problems, but I'd much rather take my best shot here because cross-Longwood really really really isn't going to work. We found that out 45 years ago when the increasingly desperate tunnel concepts the state proposed as a last-ditch effort to save I-695 were on their final death spiral. The very inclusion of that routing in the UR Phase III grade separation concepts betrays considerable amount of un-seriousness on the state's part because they know this better than anyone.

 

[vanshnookenraggen]

You're totally right. I'm trying to build something rather complicated with all these different routes coming together. Straight up, if the D-E connection is ever built the only affordable way to do it might just be a tunnel under Huntington to the Washington/Boylston St intersection with a portal after the Washington St bridge and a new subway station basically where the NE Inst of Art is with no fancy reverse connection or UR link. Just send the D straight through Huntington, have the E terminate at Reservoir.

I see any subway construction between Brookline Village and Brigham Circle using a deep bore because of the narrow street and the high water table. It still may be possible to build a multi-directional interchange somewhere around BV but it will still be rather confined. The only place where you really have the space is going to be the Brookline Ave Playground and even as I type this I can hear the uproar.

I updated the map again but here is the changed part.

There is more space to actually construct the thing and all the delicate parts aren't right next to a flood prone waterway. The portals themselves will be behind buildings and the interlocking will be under dry land, deep enough to avoid flooding issues. It also allows for Brigham Circle station to be built as a proper terminal for E trains (and provisions for a tunnel through Mission Hill for all of you who still hold out hope for Arborway restoration). It is, admittedly, a very circuitous route for the UR but given the costs of the alternative it may be the only affordable way to build it.

 

[F-Line to Dudley]

You're totally right. I'm trying to build something rather complicated with all these different routes coming together. Straight up, if the D-E connection is ever built the only affordable way to do it might just be a tunnel under Huntington to the Washington/Boylston St intersection with a portal after the Washington St bridge and a new subway station basically where the NE Inst of Art is with no fancy reverse connection or UR link. Just send the D straight through Huntington, have the E terminate at Reservoir.

I see any subway construction between Brookline Village and Brigham Circle using a deep bore because of the narrow street and the high water table. It still may be possible to build a multi-directional interchange somewhere around BV but it will still be rather confined. The only place where you really have the space is going to be the Brookline Ave Playground and even as I type this I can hear the uproar.

I updated the map again but here is the changed part.

There is more space to actually construct the thing and all the delicate parts aren't right next to a flood prone waterway. The portals themselves will be behind buildings and the interlocking will be under dry land, deep enough to avoid flooding issues. It also allows for Brigham Circle station to be built with a loop for E trains. It is, admittedly, a very circuitous route for the UR but given the costs of the alternative it may be the only affordable way to build it.

Circuitous, but the cross-Brookline boondoggle would've skipped Kenmore. Which is insane. This way burying the B to BU Bridge under the reservation + a reconfigured Kenmore with B-to-D boomerang loop (probably lower-level since the upper-level loop is C/D-to-C/D only and would be a messy modification) is at most a straightforward 6 grade separated, fare-controlled stops if the convergence is at BV, 5 if the convergence is between BV and Longwood:

-- BU Central/BU Bridge (BC branch, Harvard branch + UR/Grand Junction transfers, 47 bus).
-- BU East
-- Kenmore
-- Fenway
-- Longwood
-- Brookline Vill. (if the lines fork there)


Cross-Brookline probably would've been BU West, Kent St., Longwood, LMA or something ridiculously low-upside like that. And outside of fare control on the surface side. +1-2 stations isn't a big performance difference when it's actually connected together on subway grade separation and can fling stuff on different trajectories. Or a congestion difference when talking how much poking a tunnel to BU Bridge 2 stops out cleans up the branch merging mess coming into Kenmore.


The only non-straightforward tunneling here is the BV interface. The 1 mile to Brigham is under the reservation footprint, same as the B. Under Huntington is a pain but has the width and lack of curbside tall buildings to sidestep the building mitigation. And then, take a deep breath with the most feasible injection on that 1500 ft. x 500 ft. "study area" rectangle around BV. Acknowledging that the engineers are going to have to do their job before we know within a couple dozen-feet's accuracy where the lines feasibly are going to plot on the map.

 

[vanshnookenraggen]

-- BU Central/BU Bridge (BC branch, Harvard branch + UR/Grand Junction transfers, 57 bus).
-- BU East
-- Kenmore
-- Fenway
-- Longwood
-- Brookline Vill. (if the lines fork there)

That is needlessly messy and expensive. The only station you need is BU Central which would be built basically between the current BU Central and East stations. You'd need the space in order to have the lines interchange effectively.

A reverse at Kenmore? Why? Anyone needing to continue to Kenmore or beyond would just transfer at BU Central to the Green Line and anyone at Kenmore needing to get to Fenway/Longwood/BV would just take the D. I can't really imagine there is going to be enough of a demand for a direct Cambridgeport/MIT to Kenmore service that can't be handled by the 1 bus.

Kenmore is where you transfer to other lines but the UR and Huntington Ave ext connects those lines (except the C) before Kenmore. The only instance you would need to get so many people to Kenmore is for Sox games and since the UR stops at Fenway you don't really need it to go to Kenmore. If you are making these upgrades then the BU Central becomes more of an important transfer hub; C trains will still connect at Kenmore but if you have the Huntington Ave subway extension then that will bypass Kenmore; only those people needing to go directly to Kenmore or Hynes will use it (a large number for sure but not enough to warrant a total rebuilding of Kenmore).

And if somehow the need is so great then you could just connect the GJ UR to Lechemere and run an UR loop through the Central Subway. I don't think that is the best use of resources but it's a hell of a lot cheaper than some second level Kenmore station with some reverse service that will tie up the UR.

Edit: Also, which I totally forgot about, is the culvert for the Stoney Brook which runs under Kenmore Sq (Deerfield St IIRC) so building anything below the existing Kenmore would have to deal with that.

The only non-straightforward tunneling here is the BV interface. The 1 mile to Brigham is under the reservation footprint, same as the B. Under Huntington is a pain but has the width and lack of curbside tall buildings to sidestep the building mitigation. And then, take a deep breath with the most feasible injection on that 1500 ft. x 500 ft. "study area" rectangle around BV. Acknowledging that the engineers are going to have to do their job before we know within a couple dozen-feet's accuracy where the lines feasibly are going to plot on the map.

Huntington is fine until Brigham. Between Brigham and BV you are going to have to deep bore for multiple reasons. And yeah, so much of this depends on actual engineering studies.

 

[F-Line to Dudley]

That is needlessly messy and expensive. The only station you need is BU Central which would be built basically between the current BU Central and East stations. You'd need the space in order to have the lines interchange effectively.

Station spacing. Entrance-to-entrance that well exceeds average subway station spacing in town by a bit. Especially if you're not spitting the back up onto the surface until Pleasant St.

A reverse at Kenmore? Why? Anyone needing to continue to Kenmore or beyond would just transfer at BU Central to the Green Line and anyone at Kenmore needing to get to Fenway/Longwood/BV would just take the D. I can't really imagine there is going to be enough of a demand for a direct Cambridgeport/MIT to Kenmore service that can't be handled by the 1 bus.

1. Because that's the operational match for the Urban Ring, which goes all the way across Brookline to Longwood. That one-seat service pattern needs to be part (not all, but part) of the picture for the 66'ers who need to get from Harvard to Longwood and CT2'ers who need to do the same out of Kendall and MIT. That's where the established demand is coming off that quadrant of the Ring. That established demand does not get served without some sort of move that gets you one-seat to the Longwood vicinity.

2. You gain few to none of the radial relief benefits if everything has to cram back down the Central Subway all the same. The 'boomerang' move between the B and D at Kenmore means this only occupies capacity on the D and this new BU Bridge subway extension, where there is plenty of room to give. Prevailing service patterns can be what you want them to be, but there has to be some diverging routes and short of the impossible cross-Brookline tunnel that's the most inocuous way to do it.

Kenmore is where you transfer to other lines but the UR and Huntington Ave ext connects those lines (except the C) before Kenmore. The only instance you would need to get so many people to Kenmore is for Sox games and since the UR stops at Fenway you don't really need it to go to Kenmore. If you are making these upgrades then the BU Central becomes more of an important transfer hub; C trains will still connect at Kenmore but if you have the Huntington Ave subway extension then that will bypass Kenmore; only those people needing to go directly to Kenmore or Hynes will use it (a large number for sure but not enough to warrant a total rebuilding of Kenmore).

If the UR misses Kenmore it's not doing what it's supposed to do. Phase II (the mixed grade separation/mixed street-running BRT plan) does boomerang out at the Kenmore bus station. The stupid Phase III grade separation plan would've removed that for the cross-Brookline boondoggle. Oh, boy...transit loss. BU Central is never ever ever going to be a substitute that stands on its own as Kenmore replacement. It works as the branch transfer where the B splits from the Harvard branch and GJ LRT, but Kenmore's a non-optional destination.

Not a total rebuild of Kenmore, either. The west end of the station and the way the branch tunnels split are locked into place. Can't change that. The upper-level loop only goes C/D-to-C/D. Can't change that.

So try dipping down east of the station where the Square is at its widest in a B-to-C/D lower loop that's about as inocuous as the upper-level loop. Pick one set of platforms to stop at on this service pattern; don't stop at the same station twice. Perhaps limit your station reconfig to shaving out the width and shifting around to get a set of passing tracks for whichever platform you skip (D side's probably better for that). And you can abandon the pretty useless upper loop if that's what get you the wall-shaving space for some passing track room.

Several potential ways to do it, but because of the tunnel alignments it is a "do no harm" goal.

And if somehow the need is so great then you could just connect the GJ UR to Lechemere and run an UR loop through the Central Subway. I don't think that is the best use of resources but it's a hell of a lot cheaper than some second level Kenmore station with some reverse service that will tie up the UR.

See above. Use the B tunnel's and D's capacity without fouling the Central Subway's routing at Kenmore and it's not a capacity ceiling.

Edit: Also, which I totally forgot about, is the culvert for the Stoney Brook which runs under Kenmore Sq (Deerfield St IIRC) so building anything below the existing Kenmore would have to deal with that.

All the better reason to stick that dip-under east of the station by Raleigh St.

Huntington is fine until Brigham. Between Brigham and BV you are going to have to deep bore for multiple reasons. And yeah, so much of this depends on actual engineering studies.

Meh. You might be able to get away with cut-and-cover up until you're right about to hit Riverway. But it's not a huge deal because at least there is real bedrock around Mission Hill.