Green Line Reconfiguration

Java King

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Northland = Upper Falls, as the historic depot is at the Oak St. grade crossing and Northland is on the corner of Oak/Needham 1200 ft. away. That's the closest physical stop location.

As mentioned, the Avalon site (placemarked "Needham St. Station") was the weakest link in the proposed stop roster so unless the TOD on the corridor is so en fuego it merits an inbound spacer that one's almost certainly going to be the first cut.
That makes sense. You had originally said, Upper Falls, Fremont Street, right before 128; and that seemed too far away looking at the Google Map. :)
 

Java King

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If the Green Line Needham extension went to Needham Junction as F Line states, would Hershey be the end of the line for the Needham Commuter Rail, or would that commuter rail line have to be an Orange Line Extension to Hershey at the same time as the Green Line Extension to Needham Junction to make operational efficiency for the NEC?
 

F-Line to Dudley

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If the Green Line Needham extension went to Needham Junction as F Line states, would Hershey be the end of the line for the Needham Commuter Rail, or would that commuter rail line have to be an Orange Line Extension to Hershey at the same time as the Green Line Extension to Needham Junction to make operational efficiency for the NEC?
There would be no direct connection, and Hersey would be abandoned...but gain grade-separated rail trail extension for easy walk to Needham Jct. To compensate the 59 bus would be re-routed away from the Needham Jct. route duplication down Great Plain Ave. out of Needham Ctr., where it would direct-serve Hersey and the neighborhood by St. Sebastien's Academy before either turning @ 128 or doing something chained together through the Dedham bus desert. W. Rox (or VFW Pkwy., since the storage yard is going to be out by Millennium Park and that might cheaply serve up a'ight enough stop spacing for a 'bonus' extra stop next to Home Depot) are the end-of-line for Orange; Needham Jct. is end-of-line for Green (with station relocated to middle of wye/future-loop instead of wrapping around to the old depot building). Rail trail is backfilled from its current trail head west of the wye over 128 into City of Boston, where side-path enhancements on VFW Parkway can potentially direct-link it to the Emerald Necklace network.

Because for most of history the OL extension was to continue to (sadly now blocked) Dedham Center, not Needham/128, there is scarce data on demand for barreling across Cutler Park. Since Greendale Ave. off the Great Plain Ave. exit is mostly medium-low density single-family homes and zero mixed commercial anywhere near, it's widely speculated that a direct OL 128 siting would struggle mightily with all-day demand and run mostly empty all hours except for Pn'R rush...perhaps even needing to be cut back on late nights to W. Rox from too-low utilization. Presence of Green flanking 128 @ Highland Ave. in the TOD hotspot is going to suck up lion's share of the demand, and :15 service to Dedham Corporate on the Franklin Line cuts the legs out from such a Great Plain siting from the south. At minimum there is no way in hell that would be included in the initial build, because crossing Cutler Park for 1 stop is too expensive and too poorly-studied as of 2020 to lump in as monolith. Instead that's a consideration you can weigh pros/cons of extending later on if there's a viable hook for it. The base build, rather, stays pretty firmly Green-eats-to-Junction / Orange-eats-to-W. Rox and no over-kvetching about the middle. Hersey the least-of-all places to be concerned about, because it will be gaining a tag-team bus offset to Needham Ctr. and paved trail offset to Needham Jct. in the base build. Meeting up with vastly superior rapid transit headways when it gets there.
 
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Tallguy

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I have occasionally mused about the notion of sending some GL trolleys down to WRoxbury on the single line.....
 

nick

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When considering cost, technical feasibility, and benefits to Green Line reliability and capacity, what would be the most likely (not most wanted on this board) next GLX-like project or set of projects after the GLX? An “F Branch” extension to Dudley? Stuart or under-the-Pike realignment of the E Branch and removal of the Copley Junction? Seaport branch? Grand Junction branch?

For the sake of discussion, I’m not considering GL Transformation and Mattapan Trolley Transformation in this question since they are known and T-adopted projects. I’m more interested in thinking about realistic and likeliest next steps.
 

F-Line to Dudley

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When considering cost, technical feasibility, and benefits to Green Line reliability and capacity, what would be the most likely (not most wanted on this board) next GLX-like project or set of projects after the GLX? An “F Branch” extension to Dudley? Stuart or under-the-Pike realignment of the E Branch and removal of the Copley Junction? Seaport branch? Grand Junction branch?

For the sake of discussion, I’m not considering GL Transformation and Mattapan Trolley Transformation in this question since they are known and T-adopted projects. I’m more interested in thinking about realistic and likeliest next steps.
Probably GLX Union-Porter, because S.T.E.P. already has that earmarked as a future advocacy. Also wouldn't be any megaproject cost- or schedule-wise, which makes the follow-thru advocacy a lot easier.


Boylston-South Station + Transitway as LRT replacement for canceled Silver Line Phase III is the most five-alarm urgent, but that's not going to be so much as put to another study by this fraidy-cat Admin. Urban Ring NW quadrant should be talked up more with all the hullabaloo about Beacon Park/West Station, but that project is doing a fine job self-immolating in gridlock so also don't think that's going to be a focused discussion as long as this Admin. is in charge.
 

Tallguy

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I think that Needham comes first as Prov/Stoughton Fairmountand Franklin get electrified Needham will increasingly become "odd man out".
 

Riverside

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I spent a long time on New Year’s Eve playing around with a spreadsheet and thinking about the Bay Village Loop proposal. I’ve long been both enchanted and troubled by the idea, but really struggled to articulate my objections. I think I’ve managed to narrow it down at this point. This post was originally much longer, but I think I can make the point more succinctly. (Maybe.)

Basically, my objection comes down to, “The Bay Village Loop solves the wrong problems,” which may be a little harsh – it might be fairer to say “The Bay Village Loop solves important problems, but still leaves key issues unresolved, and thus undercuts its own benefits.”

Background

The Big Idea™ of the Bay Village Loop, like its proposed counterparts at Brickbottom and BU Bridge (and sometimes Brookline Village and/or Chestnut Hill Ave), is to reimagine the junction from a diverging Y into a multidirectional “roundabout”-like junction that allows trains to travel “branch to branch” without taking up capacity on the main trunk; in the case of the Bay Village Loop, the Central Subway north of Boylston is the main trunk.

More practically, the Bay Village Loop offers a sort of “meet in the middle” compromise that would simultaneously solve the problems of how to connect the Central Subway to a Huntington Ave Subway (via Back Bay), a LRT branch to Nubian, an LRT connection to the Silver Line Transitway, and a transfer to the Orange Line at Tufts Medical Center.

Those first two in particular are vital: an LRT line to Nubian has been the clear and obvious replacement for the El for decades, and a Huntington-Back Bay subway is critical for eliminating the bottleneck at Copley’s flat junction, and for the consolidation of the E and D Lines (necessary to open capacity for other expansions). Both of these probably should use the abandoned Tremont Street Subway, which already has a diverging flying junction to enable two branches.

These are serious needs, and the Bay Village Loop addresses them extremely elegantly. But it fails to address a more fundamental problem further north -- one that I see as threatening to the entire idea of a super-expanded Green Line.

Problem

Boylston to Park has a capacity of 40 trains per hour. (North of Park is a separate discussion, which we don’t need to deal with for this question.) Right now, those 40 trains are divided roughly evenly among four branches, to make for 6 minute peak headways (in theory, at least).

The definition of “rapid transit” is always situation-dependent, but in Boston, I would say that you need peak headways of 12 minutes or better (5 tph) to qualify as “rapid transit.” Certainly 15 minute headways would be outside the realm of “rapid transit”.

Now, on the face of it, this isn’t a problem – 40 trains per hour divided by 5 trains per hour per branch gives you 8 branches, which is roughly in the ballpark of what we usually talk about with the southern half of the LRT network:
  1. Harvard
  2. Boston College
  3. Cleveland Circle
  4. Riverside
  5. Needham
  6. Nubian

    plus maybe

  7. Oak Square
  8. Brookline Village (if all Highland Service rerouted to Huntington)
  9. Seaport
But. That’s 12-minute headways as a baseline. That’s not going to swing it on the branch to Nubian, where you definitely will need more than 5 trains per hour. (See discussion in addendum in following post.)

Robbing Peter to pay Paul

And this is where we hit my problem. As soon as you siphon a larger fraction of those 40 tph onto one branch, the others move, as a mathematical reality, out of the realm of rapid transit headways. If we assume 8 branches and 10 tph to Nubian, that alone forces every other branch to 14-minute peak headways.

And unfortunately, Nubian isn’t the only branch that would need an extra helping of those 40 tph.

The appeal of the multi-direction junction concept is to be able to bypass (literally and figuratively) those capacity limits by running extra trains on the branches that avoid the trunk. For example, the Bay Village Loop would allow extra trains on the Highland Branch to be routed instead over to the Seaport.

But there are at least three branches that would not be able to be addressed this way: Nubian, Boston College, and Harvard. Boston College and Harvard have no access to the Kenmore Loop; Harvard can be supplemented by service via the Grand Junction, but the Harvard-Kenmore service is going to be vital, particularly as Kenmore will become the transfer point for southside BRT Urban Ring. Harvard and Boston College (to say nothing of Oak Square) has no way to receive supplemental service via Kenmore – it all has to come from that pipe at Park Street.

For the sake of argument, let’s imagine that each of those three branches got 6 tph for 10-min headways. (I think this is too low anyway, but we’ll stay with it for the sake of argument.) That accounts for 18 of those 40 tph, leaving 22 tph to be divided up among Cleveland Circle, Brookline Village/Riverside/Needham (pick two of the three), and any other branches you try to add on (Oak Sq, South Huntington, Seaport, Grand Junction).

Let’s say you go with a “bare minimum” approach of six branches, each at 10-min headways (branches in italics have no supplement – strictly 10-min headways):
  • A) Harvard via Boston University
  • B) Boston College via Boston University
  • C) Cleveland Circle via Kenmore
  • D) Riverside via Kenmore
  • E) Needham via Bay Village
  • F) Nubian via Bay Village
At that point, you’re maxed out. You have 4 extra tph lying around to sprinkle on to a few branches – maybe you can lower those 10-min headways to 8-min – but that’s it.

If you want to add more branches, or improve frequencies on any particular branch, you will have to cut frequencies on other branches and move them out of rapid transit territory.

And remember: the bypass trick won’t work on branches to Harvard, Oak Square, Commonwealth, Nubian, or Grand Junction via Kenmore. So you’re again forced to choose between two bad options: prioritize those and require more forced transfers on other branches; or live with 12-15 minute peak headways.

Whither The Seaport?

And notice – through all of this, I haven’t even mentioned sending trains to the Seaport. Feeding the Seaport from the “Kenmore faucet” is workable, but feeding the Seaport from the “Park Street faucet” simply isn’t, unless you’re willing to sacrifice other branches.

Now, one positive of the Bay Village loop is that it would enable trains to run directly from Huntington to the Seaport – let’s call them the “Teal Line”, running alongside “Green Line” trains to Park Street.

There are many benefits. For one, it obviates the need for a “Track 61 shuttle”; it also sets you up for a rail replacement for Massport’s Logan Express shuttle bus service. It also provides a one-seat ride from South Station to Longwood – valuable for Fairmount and Old Colony riders. And it would increase frequencies within the Huntington Subway and optionally on any branches that feed into it.

However, there are substantial drawbacks to a Teal Line. Probably the most obvious is the lack of Blue Line transfer – and it’s a very large lack. Even with a Blue extension to Kenmore, it would require a connecting journey of three stops to reach Kenmore, Charles/MGH, Government Center or State from any of the possible Teal Line stations. Given the above problems with the “Park Street faucet,” you’re likely to see a minority of Green trains running to Park and Government Center from Huntington, so many trips will require that three-seat journey.

Likewise, riders on the Kenmore branches will also have a three-seat journey to the Seaport – whether via Kenmore-Brookline Village, Boylston-Bay Village, or Park-South Station (or a walk between Copley and Back Bay). For comparison, the current MBTA network requires three-seat journeys only for Blue-Red transfers and for Blue-Green transfers involving services that terminate at Park. Blue-to-Red and GLX and Green Line Transformation will eliminate virtually all of those, but the Bay Village loop will add more – and they will be significantly worse than the current one-stop jogs on the Green or Orange.

Revisiting the Essex Subway in the above light

Solving the “Park Street faucet” problem is – to me – the primary argument in favor of an Essex Street subway. Combined with a restoration of the abandoned Tremont Tunnels (and yes, potentially a Bay Village station to sew together Nubian and Huntington branches), an Essex Street subway would create an entirely new LRT core subway, enabling Downtown/Financial District to now be served by potentially 80 LRT trains per hour – which gives you more than enough capacity to do everything you could dream of.

An example of what this dual-subway network might look like:

South Side LRT Alt 4.png


To be clear – there are major challenges and obstacles to an Essex Subway, and it may be impossible. A Bay Village loop might be the best we can get. But solving the “Park Street faucet” problem is, to me, the fundamental question that underlies every proposed LRT expansion. An Essex Subway would solve that problem; the Bay Village loop would not.

See addenda in following post
 

Riverside

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Addendum 1: Considerations To Improve an LRT network with Bay Village but not Essex

In a world where the Bay Village loop is built and an Essex Subway is found to be impossible, I think it’s important to consider what the vulnerabilities would be to the overall network, and what can be done to ameliorate them.

Top of the list is a lack of Blue Line connection. Some ways to connect the Blue and Teal:
  • Extend the Blue Line to Brookline Village. This would necessitate a “double back” journey for riders from Longwood, but it wouldn’t be terrible. Absent a Blue Line extension, you’d definitely want high-frequency Brookline Village-Kenmore short-turns supplementing whatever else runs through beyond Kenmore.
  • Connect the Teal to the Blue at the eastern end. This moves rapidly into 100-year-pitches, things like: a third Ted Williams bore to run LRT from the Seaport to Airport station; or splitting at South Station and sending one branch up either Congress St or Atlantic Ave to State/Aquarium. (My first reaction is that the Airport connection is the better one overall, but it would need to be hashed out.)
In this world, I think it would also be wise to add a connection to enable Nubian-South Station trains (bypassing Bay Village). The Seaport subway will almost certainly have capacity, and we know from current SL4 ridership that there is a base of riders interested in this journey. This connection would allow for maintained high frequencies on Washington Street, but potentially free up some capacity in the Central Subway. Given the amount of construction that would go into a Bay Village build, adding this leg doesn’t seem like it would break the bank.

Just to help visualize, here is a map with one possible network configuration with a Teal Line. Note that here the Nubian branch is excluded from the Teal Line, but I think it would be better for Nubian to be served both by Green to Park and Teal to Seaport.

South Side LRT Alt 3.png


Addendum 2: Why Nubian needs more than 5 tph

The Better Bus Profiles for SL4 and SL5 are consistent with the Blue Book numbers from the early 2010s: of downtown-destined riders, about 75% ride to Chinatown, South Station, or Temple Place; only about a quarter alight at Tufts Medical Center. Riders want to go downtown.

Today’s E Line surface-running stretch is roughly the same length and same ridership as SL4 + SL5. The E Line runs 10 tph for 6 minute headways, which is consistent with SL4 + SL5’s combined ~12 buses per hour for 5 minute headways.

The comparison is not strictly apples to apples: LRT vehicles have a higher capacity, so you can maintain comparable throughput even with reduced frequencies. LRT vehicles also hopefully would come with better infrastructure: protected lanes, better signal prioritization, and multi-door boarding to reduce dwells.

On the other hand, LRT vehicles would likely also have a longer route and be subject to delays (assuming at least some Nubian trains throughrun past Park Street). Additionally, an LRT branch on Washington would probably attract greater ridership than the current Silver Line, giving passengers a faster journey to downtown and potentially a one-seat journey further on. Presumably, at least some riders would be diverted from the Orange Line transfer at Ruggles, and would instead transfer to the Green Line at Nubian.

So while you’d have greater capacity, you’d also probably have greater ridership.

The E-Line comparison isn’t perfect, but in general, it’s hard to imagine justifying 12-minute peak headways within core Boston as “rapid transit”, especially so close to Downtown – 2.25 miles, which is closer than Jamaica Plain, JFK/UMass, Cambridge Central Square, most of Allston and Brookline, all of Newton, Malden, and Revere, all of which enjoy comfortably better than 10-minute headways at peak.
 

F-Line to Dudley

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I'm not sure I understand all the hand-wringing here about vultured frequencies. Seems like an extreme amount of target-fixation overthinking for tinker-toy builds in which not every imaginable piece must be built and any desired imaginable pieces are are independently mountable for installment-plan assembly. This should not be forcing *any* paralyzing existential concerns whatsoever unless you were hellbent on building every single appendage to the new network all together in a some improbably compressed timespan. That's wholly unrealistic, and will never be the way it happens in real life simply because growth is going to work at different rates re: forcing the issue for any one new appendage. The whole selling point of the Reimagined GL is that the project-by-project interdependencies are explicitly minimized in time, sequence, and ultimate state of completism adding many degrees of flex to the installment plans. It makes little sense to twist self into knots with TPH kvetches about some speculated finished product when time-wise there is no finished product, and the City and its transit patterns will likely look extremely different in ways not predictable today by the time you've gotten far enough down the bucket list of network appendages to have a look at the finished product. This is very nearly the 50-year second-wave encore to the 1880-1930 first-wave buildout of the Boston rapid transit network...with network 'dynamism' as its guiding principle rather than building new route patterns where none previously existed. Did 1880 planning czars embark on laying electrified streetcar tracks in target fixation of where they wanted their so-called "Final Build" to be in 1930? Of course not...and if they did have any such target-fixation ideas initially the end result looked a hell of a lot different from what they predicted it would be because at long timespans demographics evolve beyond scope of prediction!

Step back from the brink, please. It is not a crisis requiring a more supremely perfect megaproject build if we don't have a concrete service plan for 9+ vaporware interlined branches on 1/10/2021. The whole point of modularly distributed exponential multipliers is that you grab the most obvious fricking ones when they're available and make the most sense on bang-for-buck...then weave together the services spurred by its coattails to net benefit until the next encore. Then seek the next gear in exponential multipliers. Keep an *overall* mind in choosing builds to keeping the future-proofed routing options as flush as possible because that'll make amortizing costs vs. ROI much more academic...but don't get too precious about some nebulous 50-year "everywhere to everywhere" game. The "everywheres" are a sliding scale of importance fed through long time periods and a lot of variability of change. It is not expected any more now than when the 1880 planners were Crazy Transit Pitching that every...single...envisioned...appendage will actually be built. YMMV on whether the Oak Sq. nice-to-haves rise to that occasion, or have ready fits when traffic levels on the Urban Ring routes may well trump that need. Likewise YMMV on whether any envisioned alt patterns will ever grow enough to seriously challenge their incumbent primaries as equal slices of the TPH pie. At that very long a long-game for building, any 2021-rooted assumptions going too many nth levels of detail past primary/most-wanted network cogs are probably going to be well off the mark in their 2045+ ridership assumptions to begin with. Grade on a speculation curve accordingly.

Lastly...it makes little sense to reach that far into the future for which of these patterns *need* HRT augmentation, because you're going so many decades out on a limb the predictions cannot be all that reliable. Know that 2 of the more buildable crosstown HRT lines with upside are (1) Blue Charles-Kenmore then some choose-your-adventure continuation off the Brookline Ave. tail tracks; and (2) the "Red X" Columbia Jct.-South Station-North Station/Community College and choose-your-adventure beyond via whichever of the two crosstown NSRL study alignments gets passed over for NSRL. Those (at least the "X" and any Blue past the Storrow trade-in first phase to Kenmore) are beyond speculation on the priority order, but undoubtedly exert strong gravity on Reimagined Green and change the priority order of what plug-and-play appendages go next. You can't possibly have an idea in 2021 where the interwoven sequence of crosstown HRT vs. new LRT appendages will slot, so worrying to excess about that is pointless. Once upon a time BERy/BTC worried to excess about whether the East Boston Tunnel was going to hook up to the Cambridge Subway, be reverse-branched at Charles, be part of the greater El network, be plugged into the Riverbank Subway, and a whole slew of other things like subways to Downtown Chelsea that didn't resolve themselves AT ALL until the Depression served up the Boston Revere Beach & Lynn RR...thought to be off-limits by 1890's planners when they started navel-gazing at the future Blue Line. Then it became "Oh, duh! Terraform the BRB&L to Lynn" and four-fifths of that other kvetching just went by the wayside because they'd found Blue's true calling at long last. Do you really think there won't be at least *one* such major total-unforeseen case providing new direction on how to handle Reimage-GL vs. HRT come the next 30-50 years??? Relax.


I could go into more granular detail from there, but it starts getting lost in the same speculation-upon-speculation weeds that starts divorcing this set of concerns from the real world in degrees. So I won't get that deep, because it doesn't serve any purpose except brainlock. I will say that stuff like "D-via-Huntington" is probably not going to become a primary service pattern in our lifetimes because of the built-up legacy audience (from the streetcar days) that keeps Longwood & Brookline Village strongly affiliated to Kenmore. You'll have a Needham Branch to play with when the Rail Vision does its thing, and a South Huntington attachment to Brookline Village for alt-routing that probably becomes the perma-route once the Huntington tunnel gets buried. I am pretty sure you could filet a service pie coherently from the constituent parts that offers representative flexibility. Copley Jct. also isn't going completely away, either, as an alt route when the E trunk reattaches to South End...so you aren't at a loss for further filet patterning so long as it's low-impact enough to pick its spots non-impactfully at the old level junction. At the other bi-di junctions, service appendages are going to be paid on the installment plan. Urban Ring NW probably has a base build of Union split to BU Bridge + the extended Central Subway to BU Bridge & St. Paul + a West Station stub. I do not, however, expect the full-on Harvard Sq. Branch to cross Lower Allston and the river to the Square in a uni-build or necessarily siphon a full slice of headway pie from its initial West poke. That might be two separate installments to get it finished...trans-Allston grade separation + short-term interregnum street running to Brattle Sq. or the bus tunnel, then perma-fix tunnel crossing behind prepayment. Likewise, I expect UR NE to be semi-installment: Chelsa + Logan BL station first before any combo Logan Terminals bus/trolley Transitway takes you to your flight. And maybe even a pre-pre installment of just straight-up sending the Brickbottom Carhouse leads to Sullivan superstation and re-routing C's & other flotsam there before ever paying for the Mystic crossing. Ditto Union-Porter a generation before there's any Watertown, and Watertown a generation before there's any Waltham split. For the Seaport you're trolley-stituting SL2 first and any other co-mingled patterns are just short-turning at SL Way before there's ever a City Point trolley appendage taking that up. You're also mounting things like quad-tracking across the GC station wedge as a wholly independent/in-situ project solely when as-needed for traffic sorting...not jumping the gun by 25 years because something you haven't built yet *might* some day distant put north-of-Park TPH math under stress.

Plug-and-play increments. Fewer, not greater, build interdependencies. Greater, not fewer, routing flex to shape-shift around changeable futures and changeable build priorities. Fluid priority slotting next builds...so it's grab-and-go as needed, less of a tortured studies ordeal to augment the network. And prioritized to exponential growth, which both gooses the topline ROI for each build but also minimizes the downsides for every nice-to-have appendage that doesn't end up happening when you ideally want it to, if ever. And SIMPLIFIED thinking. If we're tying ourselves into knots on run-thru service TPH's for a 50-years-from-now perfectionist network that in all likelihood is not going to exist in the exact form the best Year 2021 pedictive data would envision...you're seriously inhibiting your own ability to make meaningful improvements. 50% of the network enhancements just fuckin' built to let the chips fall as they may ends up better in the end than scare-splitting hairs now on an extra 25% of the future-beyond-that network...let alone splitting those hairs 99th percentile completion of a network you can be damn sure will not resemble 3 decades from now what your best completist guess is today. This doesn't have to be executed like hitting the proverbial five-run home-run. Just get a couple of the exponential-multiplier pieces going in the pipeline and any end result will be worlds better. nth-level midcentury traffic details can always be smoothed over by other means. By no means is this The Last Killshot for Boston rapid transit.
 
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Riverside

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I don't disagree with anything you've said, F-Line. Your whole point is to leave open options for the future so the network can expand flexibly. That's my point too. And my particular point -- which you didn't mention -- is that regardless of what you do at Bay Village, the faucet originating at Park Street can only supply (barely) rapid transit headways to 6 branches. And 5 of those are basically locked in:
  1. Commonwealth
  2. Beacon
  3. Riverside
  4. Needham
  5. Nubian *
* (Nubian should probably be listed twice on this list -- because it diverges from the trunk so close to the core, it can't benefit from doubling up à la Riverside + Needham, so it needs to have higher frequencies built in.)

If you want to add Allston, fine; or if you want to add Seaport, fine. But you can't do both. And even if you do just one, your average frequencies on each branch are going to 11-minutes. (And that's average -- some would have to be worse.) This doesn't become a problem when "adding every single imaginable appendage" -- this becomes a problem (coincidentally) as soon as we add any appendages beyond those which have been on the books for 100 years.

You raise a fair point about trying to prognosticate too far into the future, and that's very reasonable. But none of those five corridors are ever going to not merit rapid transit service to downtown. And the only physical way to feed half of them right now is from Park Street. So whatever plans we make need to account for that from the start.

If you want to both expand the Green Line and maintain its legacy services, you get enormously more flexibility by opening a second downtown tunnel. As I laid out in the addendum, you can do that with a Bay Village-South Station alignment, but it's a mixed bag because you lose a connection to Blue. Those are the kinds of things I think need to be hashed out.

Finally, on a very specific note, this is why I can't see a Park-Bay Village-Seaport service ever running. What's the point of running a roundabout service every 9 minutes? Better to send those trains on west or south to literally any other radial branch where we already know there is demand for service to downtown. Seaport could be equally well-fed by west-originating trains instead.

Overall: as far as I can see, loss of rapid transit frequencies becomes a guaranteed problem in any expansion that puts more than 6 south-originating branches into the Central Subway. Given that 5 branches are already indefinitely spoken for, the rubber hits the road on this very quickly, regardless of what kind of expansions actually happen in the next 50 years. I'm not saying that the Bay Village loop shouldn't be built -- like I said above, there are tremendous benefits -- but I think the Park Street faucet issue is more fundamental, and, like I said, undergirds pretty much any future expansion of the LRT network.
 

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Lastly...it makes little sense to reach that far into the future for which of these patterns *need* HRT augmentation, because you're going so many decades out on a limb the predictions cannot be all that reliable. Know that 2 of the more buildable crosstown HRT lines with upside are (1) Blue Charles-Kenmore then some choose-your-adventure continuation off the Brookline Ave. tail tracks; and (2) the "Red X" Columbia Jct.-South Station-North Station/Community College and choose-your-adventure beyond via whichever of the two crosstown NSRL study alignments gets passed over for NSRL. Those (at least the "X" and any Blue past the Storrow trade-in first phase to Kenmore) are beyond speculation on the priority order, but undoubtedly exert strong gravity on Reimagined Green and change the priority order of what plug-and-play appendages go next. You can't possibly have an idea in 2021 where the interwoven sequence of crosstown HRT vs. new LRT appendages will slot, so worrying to excess about that is pointless. Once upon a time BERy/BTC worried to excess about whether the East Boston Tunnel was going to hook up to the Cambridge Subway, be reverse-branched at Charles, be part of the greater El network, be plugged into the Riverbank Subway, and a whole slew of other things like subways to Downtown Chelsea that didn't resolve themselves AT ALL until the Depression served up the Boston Revere Beach & Lynn RR...thought to be off-limits by 1890's planners when they started navel-gazing at the future Blue Line. Then it became "Oh, duh! Terraform the BRB&L to Lynn" and four-fifths of that other kvetching just went by the wayside because they'd found Blue's true calling at long last. Do you really think there won't be at least *one* such major total-unforeseen case providing new direction on how to handle Reimage-GL vs. HRT come the next 30-50 years??? Relax.
Also -- what is this in response to? Unless I've missed something, my post didn't mention HRT augmentation once -- except in reference to the uncontroversial Blue-to-Kenmore.

Are you saying that suggesting that some of the branches which I'm concerned will eat up shares of the Park Street pie could be replaced by HRT in some 50-year future? If so, then, I mean, sure, I guess.

But, I mean, we've already laid out -- extensively -- why the Highland Branch is a no-go for that... which also probably means that Huntington-to-HRT doesn't help you out... maybe you could find a way to get the B Line out of the subway if paired with an HRT extension to Allston... so that's one branch, cool. But you're basically limited to whatever the Blue could hook into, unless you're talking about converting part of the Green Line into a new HRT line... but then we end up right back where we started, which is the need for a second downtown tunnel, unless you want to kick all of the LRT trains out of the Central Subway forever.

My point: if you are in a future where a Bay Village loop is a reasonable build -- meaning you have LRT to Nubian and to a new Huntington subway via Back Bay, then you are also in a future where adding more branches to the Central Subway is going to be near-impossible. It doesn't matter where those new branches are, it just matters that they feed into Park. So if it's worth planning for LRT to Nubian + Back Bay (and I believe it is), then it's worth planning for the Park Street faucet problem as well.
 

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I don't disagree with anything you've said, F-Line. Your whole point is to leave open options for the future so the network can expand flexibly. That's my point too. And my particular point -- which you didn't mention -- is that regardless of what you do at Bay Village, the faucet originating at Park Street can only supply (barely) rapid transit headways to 6 branches. And 5 of those are basically locked in:
  1. Commonwealth
  2. Beacon
  3. Riverside
  4. Needham
  5. Nubian *
* (Nubian should probably be listed twice on this list -- because it diverges from the trunk so close to the core, it can't benefit from doubling up à la Riverside + Needham, so it needs to have higher frequencies built in.)

If you want to add Allston, fine; or if you want to add Seaport, fine. But you can't do both. And even if you do just one, your average frequencies on each branch are going to 11-minutes. (And that's average -- some would have to be worse.) This doesn't become a problem when "adding every single imaginable appendage" -- this becomes a problem (coincidentally) as soon as we add any appendages beyond those which have been on the books for 100 years.

You raise a fair point about trying to prognosticate too far into the future, and that's very reasonable. But none of those five corridors are ever going to not merit rapid transit service to downtown. And the only physical way to feed half of them right now is from Park Street. So whatever plans we make need to account for that from the start.

If you want to both expand the Green Line and maintain its legacy services, you get enormously more flexibility by opening a second downtown tunnel. As I laid out in the addendum, you can do that with a Bay Village-South Station alignment, but it's a mixed bag because you lose a connection to Blue. Those are the kinds of things I think need to be hashed out.

Finally, on a very specific note, this is why I can't see a Park-Bay Village-Seaport service ever running. What's the point of running a roundabout service every 9 minutes? Better to send those trains on west or south to literally any other radial branch where we already know there is demand for service to downtown. Seaport could be equally well-fed by west-originating trains instead.

Overall: as far as I can see, loss of rapid transit frequencies becomes a guaranteed problem in any expansion that puts more than 6 south-originating branches into the Central Subway. Given that 5 branches are already indefinitely spoken for, the rubber hits the road on this very quickly, regardless of what kind of expansions actually happen in the next 50 years. I'm not saying that the Bay Village loop shouldn't be built -- like I said above, there are tremendous benefits -- but I think the Park Street faucet issue is more fundamental, and, like I said, undergirds pretty much any future expansion of the LRT network.
I'm not sure I agree on the "Park St. can't support it" basis. Park St. supported more than today when the last incarnation of Bay Vill was active for City Point, Egleston, and Dudley branch service. It did so because transfer dwells were smaller and trains got in/out of the station faster. That's what we want more of: elimination of the double-transfer dwells to SS/Seaport so more people are staying on the train @ Park instead of chewing doors-open time hopping on/off and blocking the ped grade crossing on the IB outer track from faster train starts by virtue of racing to/from the Red level. If doors are closing faster and trains are clearing the platform faster, throughput raises to >40 TPH by some calculable margin.

That's not a real lofty goal all things considered. It's easily achievable with the most-wanted augmentations...plus a bunch of Ring alt patterns that move more bodies above-and-beyond without even entering the Central Subway.

And where HRT augmentations do matter towards that goal is BLX-Kenmore taking a big chunk out of the westward trunk traffic to be reassigned to other patterns. That phase of expansion is the least speculative because Storrow midsection trade-in is the only set of conditions putting it on the table. But the load relief @ Park is LARGE and direct-targeted as a result.

So you have all of that load reshaping above carving out more headroom @ Park proper. Plus the option to quad up GC to eliminate the only above-and-beyond bottleneck with platform slotting. Plus the option (if necessary...probably isn't) to quad up Haymarket with narrower separate islands to play the same ahead/behind platform slotting throttle with North Station. Plus...jeez, if that isn't enough...simply linear-combining Park-Boylston into some block-spanning superstation monster if that somehow adds something extra on top (as with Haymarket probably also unnecessary and too little fluff value-added for its price). All to allow a LARGE-scale augmenting of the network that no one is expecting is going to split decimal points on 99th percentile completism, if we were even capable of predicting that far.

I'm not seeing where there's a looming crisis in all that causing ANY hesitation whatsoever in building the flexi junctions. And even if there were, absolutely no one is putting a gun to dispatch's heads to saturate each and every flexi junction with service levels to their outermost capacity limits. If on further review the comfiest ceiling is a little lower than breakneck-max...so be it. Maybe your South Huntington service to Hyde Sq. or Forest Hills rides the Copley Jct. alt route to Park Loop exactly like the old days while trunk Huntington service takes the South End thru-and-thru...neither interacting with each other on any track past the new level split abutting Prudential. For the ROI you're still exponentially expanding service levels and service routing flex as a Very Good Thing™, so glass-half-empty concessions like ^^getting extra-creative with track sharing keep-away^^ are part/parcel an outflow of the extra flex. We aren't hurling ourselves headlong into new-creation walls by embarking on this; we're actively avoiding such bottlenecks, even when actual traffic modeling games out on the more-pessimistic side than our best crayon-draw hopes.


This is only a problem if you assume present-day constraints @ Park are a forever thing and every service is sharing the same track. Well...they weren't a forever thing as matter of historical record, and there are direct targets in the highest-priority builds for addressing that ceiling. So it stands to reason that 40 TPH is not going to be the forever-and-forever ceiling, despite it being negotiable exactly how much more headroom is available in any given load-relief build. So right then and there we aren't dealing with immovable objects, and a large share of this concern is subject to the sliding scale of which particular offsets you prioritize first.


That's my overall objection: the cap isn't a fixed number in the absolute. And also isn't fixed in where it's apportioned service-wise because of the mass ridership shape-shift that takes place with some of these augments (esp. the highest-priority projects that outright remove transfer door dwells from that station as first order of business).
 
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F-Line to Dudley

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Continuing the thought on fileting South Huntington service to Park Loop via Copley rather than run-thru via Bay Village. . .

Also consider "the lost art of short-turning", of similar ilk. The 3-1/2 loops on the Central Subway become much more important players in our Reimagined universe. The modern T has pretty much abdicated the use of service-filet short-turns ever since the Arborway-Park vs. rush-hour Heath-Lechmere augments ended in 1985. That practice is readily encouraged again with Reimagining.

Take for instance the Ring largely displacing the 66 bus's crosstown audience, achieved primarily by having Kenmore run-thrus from the Harvard Branch. Since there won't be corresponding SW quadrant LRT owing to lack of ROW's and the upstairs bus station transfer to Longwood/Nubian BRT will be somewhat capacity-limited...you probably achieve ideal load balance by wrapping some E supplementals inbound @ Brookline Village to loop at Kenmore Loop. Steps up the frequencies for the 66'ers to have more Longwood trains, while the extra trains stay 100% track-separated on the C/D-to-C/D loop from all the B/Ring service heading thru on the other sides of the island platforms. The terraforming of the 66 trunk via LRT is thus a service that doesn't hit the Central Subway equally with all of its routing components given how the Loop is leveraged for the quick cross-platform Longwood transfer.

Take as another instance the art of reaching Nubian direct from Kenmore. Streamlined enough the BRT you'll have to live with on the south-half Urban Ring should be plenty good enough to bear its representative ridership load, but in similar fashion to the "66'er"/Longwood augments there's nothing stopping you from running wraparound E's from Kenmore Loop to Brookline Village...down Huntington...then run thru the wye at Bay Village flexi-junction straight on to the Seaport-v.-Washington split instead of continuing into the Central Subway like most E's. Now...this probably doesn't need to be a frequent filet pattern to do its stated job of keeping the BRT SW Ring buses appropriately free from crowding and over-long dwells. Maybe one turn every 12 mins. does the job. But it can do the job without touching any trunkline track, which in turn takes small but meaningful edge off Park St. TPH management in addition to directly helping the more-direct routed BRT Ring's OTP immensely. When the alt routes such as these are small-stakes but evenly spread around the network, the traffic savings start to add up on the trunks of greatest concern.

Park Loop (if/when GLT trades the too-tight inner loop back to reactivation of the wider 1960's-abandoned outer loop), GC Loop + opposite-direction Brattle Loop, and Kenmore Loop are all exploitable assets here on the throttles. Certainly any inbound-from-Lechmere UR service that isn't run thru directly to the Seaport is likely to terminate @ Brattle Loop most of the time. So, say, if the NE/Logan quadrant takes up a primary Seaport pattern as an SL3 replacement and the Medford Branch serves as the other primary Seaport run-thru...that means the NW Ring quadrant through Cambridge is probably going to loop @ GC more often than not. Which would make sense since it already is taking up a large share of Red load relief to Kendall and will touch RL-Harvard on any Harvard Branch run-thrus, and thus would have the smallest share of any Lechmere-originating service needing the direct Park/RL touch. Similarly any 'circuit' Ring service going Lechmere and bending back in at BU Bridge to Kenmore can potentially use Brattle Loop on one end and Park St. Loop on the other end to stay completely traffic-separated from all else on the Park platforms-to-GC platforms stretch of maximal traffic pinch while still covering every single station and transfer on the circuit. That all helps a ton, as it will not need to tally on the "40 TPH" thru-Park tracks at all with that bit of artful-yet-completist avoidance.

Similarly, you can template the old "Arborway-Park"-vs.-"Heath-Lechmere" service overlap differentiators on some of the more expansive linear pokes. For example, if Heath begats Hyde Sq. begats potentially Forest Hills you're probably not running all that thru to the Union/Porter branch. In that case assignments work better with GC looping the outermost streetcars, Union/Porter taking up something differently load-bearing, and the routes with the most streetcar miles having sparser headways than the branch & Ring trunks with greater grade separation. But can also work with 12 min. Forest Hills-GC headways being paired with 12 min. Forest Hills-Kenmore Loop headways via Brookline Village to flesh it out while playing keep-away. Sort of the same way Nubian can get a targeted augmenting via Kenmore + Bay Vill for backstopping the BRT south-half ring and also boosting Washington St. streetcar headways without a corresponding load on the Central Subway. I could see similar--if more complex--dynamics working for Oak Sq.: (1) BC vs. Oak frequencies coming out of St. Paul portal get a differing 'tweener' slice of the pie for slightly denser-than-6 min. headways to Packards but slightly sparser-than-6 headways after they split; (2) service weights a little more to the Brighton side of Packards split than Comm Ave.; (3) C trains are permanently extended via Chestnut Hill Ave. to BC as an outer service-increase augment (counterbalanced by -3 stop consolidation on Beacon as prereq), leaving only the most ridership-diffuse area of B up the hill between Harvard & Chestnut Hill Aves. dealing with the sparser headways; (4) the respective Comm vs. Brighton Harvard Ave. stops each get countdown timers for the other branch's service across the block for last-minute changes.

In large part we AREN'T hyper-focusing on the flexi-junctions as sole center of the New World Order. Blast-from-the-past via creative use of the loops to cut loads without touching the most-congested trunks is a big part of the service increase. So is asynchronous loading (e.g. Oak > BC @ Packards if the C shores up the other end; multiple pathways to Nubian by tandem BRT & alt-LRT Ring'ing; South Huntington being an open multi-routing prospect) where that shoe fits the overall traffic profile, esp. when streetcar mileage has to be dispatched. Throw enough of that confetti at the board and you do accumulate offsets for the Park area of max traffic concern.


And finally...just note how the gravitational pull overall from the radials starts and ^^all of the above^^ creative service fileting and short-turning starts slowly but surely moving away from Park St. as singular center of the universe. GC becomes way more important with the combo of Red-Blue and Brattle Loop taking up load-bearing properties and prying double-transerees away from milling around the Park platforms keeping doors open. And if BLX-Kenmore ever comes to pass, then the torch is thoroughly passed to GC >> Park as a transfer of magnitude and the bulk of your dwell-driven loading problems @ Park truly perma-disappear. It'll still carry mega thru ridership, but more people will be staying put on the trains when stopped there rather than running like ants all over the platform and stairs solely for the transfer. And that...depending on what magnitude of shift you shoot for in the gravitational pry-away...is worth its weight in substantial TPH increases by virtue of doors closing and trains starting in half the time.

It's hard to parse because all of these benefits are buried in there as part of the 'exponentialness' of the service increasers. You just have to slot your build priorities by bang-for-buck orders of magnitude to reap the benefits. Whether those benefits are exactly as broad as your best hopes would be or somewhat less due to unforseen constraints...it still substantially moves the needle of traffic management because of its innate 'exponentialness' at reshaping. That's why Reimagining is way more a new base philosophy for LRT in Boston than any discrete series of builds.
 
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Shepard

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Essex Street routing is a no-brainer. I realize it's more difficult to dig under Essex Street to reach the Seaport than the jog down to the pike and back up. But if the political will existed to get it done, there's no reason why it couldn't be done.
 

George_Apley

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For me the biggest challenge with the Essex Routing isn't the Essex St tunnel itself (though that does have challenges), it's the tie-in to Green.

Essex St routing would probably require a lot of work to be done on the Boylston St subway west of Boylston station. In order for the Green Line to be able to hook up to an Essex Street subway, we have to route some Boylston St subway trains off of the main-track that goes to Park and sending them down to a Boylston Under station that underpins the old turn-of-the-century station and then continues under Essex to meet the Transitway.
Essex St subway wouldn't be accessible from the Tremont St subway at all (unless you really blow everything up for a whole new set of flying junctions). It would also probably require getting rid of the defunct but extant flyover junction that continues south on Tremont, effectively blocking future extensions to Nubian.

The allure of the "jog" is that the Green tie-in largely uses existing infrastructure. The routing flips the above on its head; only trains from Tremont St subway can go to the Seaport rather than Boylston subway... BUT... when you look at it holistically, the "jog" routing also gets you the future parallel Back Bay routing to Huntington Ave subway leading to a future tie-in at Brookline Village, which would allow western GL routes to access the Seaport that way. Also it doesn't block a branch to Nubian. I like the jog because of those future possibilities AND the simpler integration with the existing Green Line.
 

F-Line to Dudley

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Essex Street routing is a no-brainer. I realize it's more difficult to dig under Essex Street to reach the Seaport than the jog down to the pike and back up. But if the political will existed to get it done, there's no reason why it couldn't be done.
This logic doesn't wash. Yes...the political will once existed. But political will wasn't what failed Silver Line Phase III. The project's own design failed itself by choosing too constrained a path. The lethal blowouts were the structural underpins of legacy transit infrastructure at Chinatown Station (tri-level build with double-deck BRT platforms stacked underneath an already labyrinthine 1908 OL level) and Boylston Station (deep-cavern build with painfully tight turning loop and extreme-invasive elevator mods to the GL level to accommodate). Originally they had hoped to run service thru in conjoined fashion from Nubian to Seaport, with Boylston Loop being a thru-service creation only there to square the sharp turn angle from Tremont to Essex on a 60-footer bus. Things immediately came unglued there. The bi-level squeeze @ Chinatown required climbing grades at the outer feasible capabilities of the BRT mode, incurring a performance penalty so total that schedule-keeping could no longer be planned portal-to-portal and needed a central short-turn for the sake of preserving headways. EIS'ing problems around the Common and unforeseen archeological finds at the perimeter of Central Burying Ground meant Boylston Loop had to be much tighter and slower...and Boylston Station a much more constipated transfer point because the lower level was going to be plagued by newfound dwells from every bus from either direction looping instead of running thru. In turn that kicked the last leg out from running underneath Tremont St. on an alignment very well-studied in the mid-70's under LRT because that now performance-maimed loop could no longer serve its original function of squaring the tight turn angles between Tremont & Essex for thru buses. It was way narrower now, and the Chinatown slow zone had ended hopes of run-thru. Tremont alingment was already collapsing from the manifold problems in nuking/rebuilding the abandoned trolley tunnel for a new BRT tunnel, as the utility spaghetti was too much more complicated than anticipated for the senseless construction do-over of that tunnel to stand on its own. A truly embarassing number of not-Tremont alternate alignments then had to be studied...culminating in the choice of Charles St. South. ALL of the study options added more underpinning cost to the active GL tunnel west of Boylston, and then an invasive directional change when it departed from the GL alignment to a southbound side street. Charles S. shaking out as the "least-worst" of the options after Tremont fell apart had some things (wide street width, less disruption to Common & Public Gardens) going for it...but in the end they were set to 1:1 underpinning an extra 725 ft. of Green Line tunnel hell or high water when originally they'd just try to bang a corner at Boylston Loop and get outta there; the structural underpin blowouts were now hard-coded.

And what's more...at the time the plug was pulled there was still all kinds of un-staunched bleeding around Boylston as the new, narrower, shittier Loop was still incurring all kinds of problems around the Common while building foundations scuffed up the narrowest-squeeze portion of Essex (which goes sub- 40 ft. in some spots). In the end it was killed NOT because of faltering local political will (a la Red-Blue)...but because the FTA withdrew its tentative %-match funding commitment by slapping it with a Low rating. That immediately disqualified it from any Fed support on advancing 80% design to 100% & shovel-ready...so it was D.O.A. right there. State couldn't afford by its lonesome to make up the shortfall. We never even sniffed the "Build" part because Design is where it all shit the bed. No amount of polical "will" makes that calamity surviveable.


The literal only way to address this is to go point-by-point through every specific area where the SL III design incurred itself a project-killing blowout, and fix the blowout at its source.

  1. When the sources of blowouts were the structural underpins of stations...you can no longer stake a reboot to doing any Boylston Under in any form. Doesn't matter if it's LRT bursting straight-line off Essex on a minimalist lower level, no Common-fouling loop, straight-up ramping up to a westbound junction somewhere between Arlington. You haven't checked off that box that gets the FTA reinstating the only funding source that makes 100% design payable unless you do away with anything/everything "Under" at Boylston. Extant outer tracks on the extant islands with north-south trajectory into the old trolley tunnel or GTFO for Fed fun bux.
  2. When the sources of blowouts were structural underpins of stations AND mode performance degradation as direct result of the underpins...tri-level Chinatown is out. Must be an offset and prepayment mezzanine-connected Tufts instead...full-stop. LRT on Essex would still have to stack itself to fit platforms underneath the 1908 OL level because the street is too fucking narrow where it crosses Washington to bulb out platforms on a uni-level. While fixed-guideway LRT can take steeper max grades at higher speed than BRT it's still a sucky performance demerit and lousy constipator at the line transfer. Compromised enough that most South End 'jog' alts will make equal-or-better clock time on longer tunneling feet by not having to overcompromise at the transfer stop. Again...don't address the Design fatality at Chinatown, no chance of recommitted Fed funding.
  3. When blowout sources were building mitigations on too-narrow a street, you must do better than Essex...which constrains itself to sub-40 ft. at couple particularly nasty pinches bookended by tall building foundations. Tremont from the old tunnel to Marginal is 70 ft. sidewalk-to-sidewalk; Shawmut 65 ft.; Stuart/Kneeland from Tremont 80+ ft.; Marginal/Hudson 55 ft. Even a real reach like Beach St. stays just north of 40. Crow-flies directness of the Essex route doesn't matter; it was an unbounded cost chew because they kept getting dinged with new mitigation overruns on every closer look. LRT dimensions are barely different (remember...we build every new-construction RT tunnel to maxi Red Line dimensions, so potential savings here are inconsequential inches not feet). When there appeared to be no end to the drip, drip, drip of mitigation costs, FTA couldn't in good faith keep throwing good money at bad. Any reboot must direct-address the drip, drip, drip of Essex being too-narrow a street...or it's no-go.
  4. When the sources of bloat were too many Old Boston streets with poorly-mapped spaghetti utility layers and not enough of the 1965 Pike/Urban Renewal nuke zone. Essex is a "Thar Be Dragons!" sandwich layer from Boylston to Chinatown Park, and the Tremont-Charles S. block the same (in addition to requiring structural underpin of the GL tunnel and too-close shave to the Common). Any Design reboot seeking FTA rating reinstatement must address this demerit by choosing cleaner under-street guts along majority of the new-tunneling length. Kneeland is the border zone between new & old...but being an ultra-wide post-1920 "proto-Urban Renewal" add-a-lane job like Cambridge St. the linear costs track almost exactly with Red-Blue, a project we know we can do within-estimate. Tremont/Shawmut/Marginal/Hudson are all entirely in the '65 nuke zone with accurate utility mapping. When utility relocation is such a massive and variable outlay, your 'directest' route is less about 2D than about what lurks 3D.

Again...doesn't matter if these sound like compromises. We aren't flinging this out into ether like a most-perfect Crazy Transit Pitch. This is an unbuilt mandate with previous funding commitments that should've been open for biz decade ago. But wasn't because it accrued so many fatal flaws it couldn't finish its own 100% design...and was already a performance-crippled shit sandwich well before that point of no return. We aren't reimagining it; we're rehabilitating it to fundable state. Yes...we're changing modes in the process, but BRT inefficiency vs. LRT efficiency wasn't where the FTA had to say "enough is enough" in first place. All we are doing is tit-for-tat addressing what went wrong with **specific** return volleys for every fatality vector. Then rolling back a whole lot of overcompensation cruft (incl. LRT substitution) to further simplify after the new-chosen alignments check those FTA-fix boxes. It's still fulfilling the same mandate as before...and thus (despite the generation's difference in FTA leadership) makes a direct plea for reinstated 100% Design funding that the feds will be hard-pressed to ignore and well-encouraged to fulfill simply because of that fix paper trail.

It'll get the advance-to-100% Design process fully back on-track, and then we figure out how to swallow the big bucks on Build once it's got that much reinstated momentum. But the base-most rules for engagement mandate that you're going to have to give up the Crazy Transit Pitching notion of having your favoritest Essex routing in the process. The FTA will not play ball, and their recommitment is the holdup here. So if Essex got flagged as the reason for an FTA rating fatality, then Essex is no-go, O-V-E-R. That's unavoidable fact of the task at hand. Argue till cows come home about which not-Essex routing is best for the reboot instead...because there are factually multiple candidates that would suffice for the FTA re-rating. Some 'jogs' with much higher probabilities than others, but still multiple candidates.
 
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Arlington

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Nit: When the Blue (or Green) goes along Storrow, I think it only needs 2 double-ended stations: MassAve-Gloucester and Clarendon-Berkeley
 

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Couldn't a green Line tunnel along Essex Street be deep enough to avoid undue impacts on Boylston Station and the Orange Line tunnel? If you started the tunnel to come off the existing Green Line tunnel between Charles Street and Arlington Street, begin dropping immediately and pass under both levels of tracks at Boylston Station (some underpinning of Boylston Station required ) and keep dropping (with a deep bore) to be well under any utilities and foundations along Essex Street, pass under the SB Central Artery tunnel, then rise up to meet the busway tunnel at SS, it seems that it should be doable.

The Post Office Square extension proposed and designed pre WW-1 had a similar trajectory on its west half:

 
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George_Apley

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Couldn't a green Line tunnel along Essex Street be deep enough to avoid undue impacts on Boylston Station and the Orange Line tunnel? If you started the tunnel to come off the existing Green Line tunnel between Charles Street and Arlington Street, begin dropping immediately and pass under both levels of tracks at Boylston Station (some underpinning of Boylston Station required ) and keep dropping (with a deep bore) to be well under any utilities and foundations along Essex Street, pass under the SB Central Artery tunnel, then rise up to meet the busway tunnel at SS, it seems that it should be doable.

The Post Office Square extension proposed and designed pre WW-1 had a similar trajectory on its west half:
You're still going to be interacting with the old stations with mezzanines or certainly elevators. How deep are you thinking that would not impact subterranean environs above it?
 

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