I actually don't think they would be any different than what the branch lines have for headways currently it spreads the load across more tracks than today. The only cutbacks may have to be D2 stopping at Park Street because of the track reduction past Park Street aside from that I don't think they headways would get below the headways that are currently supported on the branch lines.
F-Line could probably give a better idea of any issues that might occur.
Reopening the Tremont tunnel for any services can be accommodated without overstressing the subway by modding the Park St. inbound inner track with crossovers for thru service. The T was awarded a $12M fed grant 7 years ago to do exactly that, which entailed moving some supports and electrical boxes behind the Red Line stairs so they had a clear path to spur a crossover off the loop track. Engineering assessment turned up some complications that effectively doubled the price, and since for GLX's purposes this was a "nice to have" but not essential piece they canceled it and returned the grant.
Revisiting that now that they know what it would entail greatly helps the traffic sorting because:
- You can wave trains running past GC to their spot on the far-end GC platform without getting stuck behind a GC-turning train on the near-end. Important OTP check on the longer-haul schedules to always give them priority.
- GC-turning trains can turn faster with the orderly sorting if they also aren't stuck in an inbound traffic jam, making trains (esp. B's) less likely to start their runs late.
- With outer-tracks Tremont trains (esp. whenever E's get relocated off Copley Jct.) you can keep them track assignments completely grade-separated through Boylston and Park without needing to cross over each other, simplifying downtown dispatching to just the GC-Park pick-'em.
The Park inner crossover install would be one of the very first capacity management things you do upon first post-GLX service addition. And then benefits accrue from there.
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These things--all very short-term and
NOW priorities--done in a package solve most of the bunching problems that grind the subway to a halt:
- Signal priority on B/C/E. This fixes the "garbage-in, garbage-out" bunching situation at the portals that leaves schedules hopelessly hosed before they ever mash into each other at Kenmore or Copley. Can't be understated how much chaos evaporates when there's some sane degree of projectable schedule certainty on the branches. The GL would work for the first time in decades if real trolley signal priority were implemented.
- 3-car trains at peak and any off-peak surge slots (e.g. Fri./Sat. evenings on B) on all lines except E (Heath St. loop limited to 2-car unless widened out slightly onto the VA Hospital back employee lot). You can relax headways very slightly (minus 1-2 mins max) and still achieve a net increase in capacity by restoring the uncertainty-cushion in the schedule that's been stripped out in recent years. This covers any remaining variance left on the surface branches that signal priority doesn't account for, and allows for very precise subway dispatching. And possibly expansion slots to assign to a new service if that locktight precision frees up more infill slots.
- Proof-of-payment and all-doors boarding. Goes without saying that is massive for taming variable platform dwell times that contribute to blown schedules.
- Time to whack Brandon Hall and Dean St. on the C, and Fenwood + Back o' th' Hill on E. Time to flip Chestnut Hill Ave. to the opposite side of the intersection so alt. routed C run-thrus to BC are possible. Obviously this whole stop spacing reconfig process is beginning on the B with Comm Ave. Phase II.
- Time to triage with MassHighway, BTD, and BRA/BDPA on street-level reconfig with some redevelopment overspill to correct some deteriorated traffic conditions that have harmed transit reliability on specific streets. It'd be huge if Comm Ave. Phase II were accompanied by a reconfig of the BU Bridge intersection clusterfuck, a real B schedule-murderer. Get rid of the Carlton St. chaos and consolidate to a single-point intersection with single thru + protected-left light cycle. Do later Comm Ave. Phase III right by moving the reservation to the center, widening the cramped Harvard Ave. platforms, and sticking a pocket yard between Harvard and Griggs for short-turns and stuffing dead trains. See if the ugly-ass gas station on the corner of Huntington/S. Huntington can possibly be taken to bump-out the intersection around a realish platform...and maybe (caveat: abutter resistance) negotiate with Mission Park Apt.'s on their front parking row to bump out Huntington ultra-wide for a one-block cameo reappearance of the full trolley reservation for a real ADA platform @ MP. More platforms on all the reservation branches also need to be ADA'd as offset on either side of an intersection to maximize the precision of the traffic light signal priority.
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De-congestion effects at overcrowded transfer stations from other builds. . .
- Red-Blue takes beneficial foot-traffic off the crowded Park St. platforms and stairs by taming the double-transfers going from Blue to Red. Saves on Green dwell times at both Park (where it matters most) and GC.
- Any service running to Tufts, with its west-side Orange transfer, has moderate amounts of the same effect. Fewer people getting on/off and milling around the Park platforms (especially when it's changing off a GC-turning train to catch a North Station or Lechmere train), more people staying on the train. Think how many people are jumping across the tracks to hit the Winter St. concourse, and how much that harms dwells.
- Direct South Station/Seaport connector does VERY dramatic savings to both levels of Park. You're now at the point where foot traffic is outright uncongested.
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De-congestion effects from other Green builds. . .
- E relocation is huge by load-shifting to Back Bay over Copley. Eliminates the awful traffic-killing at-grade junction and frees up MORE capacity for branches out of Kenmore.
- E relocation via Back Bay puts another branch under grade separation between Park and Boylston, making the inner and outer tracks more or less load-balanced on traffic. In combo with the Copley de-congestion flow improves greatly all points Park & west.
- If Blue replaces Storrow, you have an immense load reduction on all Kenmore branches since Blue will be the fastest and highest-capacity one-seat out there. Many more branching or Urban Ring opportunities if this happens.
- Urban Ring north half via the Grand Junction obviously does a lot in its own right from alternate service patterns leveraging Lechmere and the less-congested north end of GC/Brattle loop for a downtown terminus. Makes the traffic skew through the gut of GC/Park far less pronounced.
- Urban Ring south half (assuming you can fashion it coherently on LRT...excessive surface running does give BRT some advantages) can leverage E-to-Brookline Village and D-to-Kenmore Loop for fast cross-platform transfers to all destinations without overburdening Kenmore-Park sending every single train through. More Kenmore capacity for 'traditional' branching and north-half Ring (Kenmore loop inaccessible from the B portal). Cross-platform definitely has huge advantages the more diverging routes you have available at Kenmore: Blue, UR, diverging branches, alt. E service patterns via the Brookline Vill. connection, alt. South Station/Seaport-via-E and Dudley-via-E patterns. Fully built-out, Kenmore cross-platform can get you literally anywhere.
Just keep in mind, the 1897 subway as originally built was a big circulator blender of routes fanning out all over the city and running in a blur of alt. routes. It didn't change into a fixed-route trunkline until the 1910's. It didn't change into a rigid long-haul line mimicking Red until 1959. It didn't shed the art of mixed short-turning (i.e. the "slash" letter rollsigns) until the MBTA era early-60's to mid-80's. It didn't start really decaying under load until late-90's New Boston boom times sent demand and congestion spiraling through the roof, deferred maintenance started taking its toll, and the Breda lemons started imposing schedule-lengthening speed restrictions.
Today's brokenness was not an everlasting condition. It can not only be rolled back by those sensible and not-very-expensive ^^short-term^^ fixes, but these other *NECESSARY* critical load relief builds like Red-Blue and Downtown-Seaport have the same effects on Park & GC dwells on GL as they do bailing out Red's slow death SS/DTX/Park. Then throw on all the universe of alt. patterns, interconnections, radials, other transfer nodes (Tufts, etc.) spread out from the Central Subway & Park/GC center of the universe and you end up re-casting Green as less a Red-like trunk that has to carry the world on its back and more that circulator it was originally built to be in 1897. In no way do you have to build
everything on the fantasy map. I'd expect E-to-BBY to trail the more critical Seaport connector by many, many years simply on project priority, and stuff like Blue-Kenmore has other dependencies like a Storrow Dr. teardown that are beyond prediction in 2016. But all it takes is a couple of the non-optional ones like Seaport-Boylston and Red-Blue to start evolving things back in that direction.
The role starts changing and the bandwidth for other things starts coming available the second you start prying away the extracurricular transfer hordes at Park & GC. And of course we know we don't have a choice but to do that much before New Boston's growth cap starts getting pinched off by those choked transfers. Green's evolution is not that far-fetched. How far you want to ultimately take it is up for debate; we have the whole Green Line Reconfig thread for that. But evolution is non-optional with the stark economic consequences of not evolving. Baseline functioning with the ^^short-term^^ fixes is even less far-fetched, less a reach on resource commitments, and more necessary. That in itself is an evolution.
So think of this in terms of scalability. Eat-your-peas fixes for healthy functioning starts on the scale by restoring lost capacity and reliability. The non-optional Downtown de-clogger builds accelerate it by cleaning up the transfer congestion. And every little thing big and small you pile on top of that adds greater degrees of scale until you pass a point where Green is back to being a real circulator and not so much a square-peg trunk.
