Your frequency map looks cool! I need to read the analysis more carefully, but looks interesting too!
My analysis wasn't really that much fleshed out. It's mostly just a rough thought exercise idea that really fascinates me for some reason, (since it's just really impractical and I wanted to take it to the most extreme, I have little intent to ever make this concept semi-plausible). Anyhow, if you would like the detailed thought process, here goes:
Regarding the Old Colony corridor, my initial map did not include Quincy Center as part of the core "mainline ROW metro service for all BERy stations" network at all, as it was outside the original BERy territory. While I could easily add corridors to Lynn and Waltham with simple extensions from the BERy terminals to reach Lynn and Waltham's major terminals, adding in Quincy Center essentially had me redoing through running for the entire BERy area.
My original map (
on the first page), had 9 northside and 9 southside routes (I piggybacked the abandoned Harvard branch to use the very impractical Track 61 terminal (
which had actual proposals for passenger service); every single radial ROW that ever existed, even once, was going to assigned a route via NSRL).
This gave me the following: (this does
NOT match the frequency map above)
* 2 branches to West Rox, Harrison Sq, Lansdowne, Porter, Magoun, Wellington, & Encore/Sweetser Cir.
* 3 branches to Forest Hills, Prospect Hill
* 4 branches to Sullivan, Broadway
* 5 branches to Back Bay
(The minimum 7 tph frequency standard for BERy stations was going to be strict, so West Rox's VFW Parkway and Spring St stations needed to hit that standard despite being past the fork, but still inside BERy territory; 11 tph would be the max so 2 branches could share a duel track at 22 tph)
To slot in Quincy Center into the network. I opted to reuse/reactivate the original Saugus Branch's abandoned connection from Malden Square/Linden Sq. to Edgeworth/Wellington. This gave me a Linden Square via Wellington & Edgeworth instead of via Encore/Sweetser Circle; that I could use as the 10th route pairing on the northside, so I could send a Quincy Center route as a 10th route piling into the NSRL tunnel (which already had 9 branches feeding into it, so I guess that'll be 110 tph just for metro-style urban rail services downtown, or 10 tracks dedicated for such purpose. Yeah, I'm being insane/impractical/unreasonable
)
(Is that a Linden Square <> Davis Square service I spy?
)
And in that process of slotting in my extension of the "mainline ROW metro network" to Quincy Center, I would have cannablized this quoted route (though I could start it from Jeffries Point and run through the Grand Junction, then do the loopy Sullivan --> East Somerville). One of my major problems is that the Grand Junction does not have a direct connection to the East Somerville - Magoun Sq corridor unless I either:
1. reroute the B & L mainline coming from Magoun Sq./East Somerville to use the GLX <---> Fitchburg ROW alignment to reach North Station, which violates the "only follow mainline ROWs principle" concept.
2. Build a station in the middle of the inner belt to facilitate transfers from Grand Junction <--> East Somerville/Magoun Sq.
(this is NE of the proposed "Brickbottom" station from TransitMatters along McGrath Hwy).
(Getting a direct connection from Grand Junction in Cambridge/Chelsea/Eastie <---> East Somerville/Magoun Sq., would allow me to cannabalize 2 of the 3 crosstown routes and only have a single crosstown route with single transfers, which would allow me to properly have enough capacity on the main branches to feed into the NSRL tunnel. Right now I've got capacity eaten up along the B & A and B & L for crosstown services that currently are separate routes, due to the lack of this connection)
Anyhow, with a Quincy Center branch. This changes my calculus completely, with the changes in bold:
* 2 branches to West Rox,
Neponset, Lansdowne, Porter, Magoun, & Encore/Sweetser Cir.
* 3 branches to Forest Hills, Prospect Hill,
Harrison Sq, and
Wellington
* 4 branches to
<none>
* 5 branches to Back Bay
, Sullivan, Broadway
Since my primary goal of my thought exercise was to serve the densely populated BERy service area with metro frequencies with 7 tph minimum, for all BERy stations/all day, my thought was that the last terminal serviced by BERy routes, or town lines (Oak Grove, West Medford, Revere St., VFW Parkway, Arlington Heights, Readville, Newton Corner, etc.), would become the route terminals, or at least every other train turning around. The only exceptions would be to service the Waltham, Lynn, and Quincy terminals with full metro frequencies of the 7tph minimum standard for metro style service. The reason being is that once one exits the BERy service area, the longer distances and less density between stops would be unsuitable for full 7 tph (of either mainline trains or metro trains) at all service hours. Only the BERy service area, and the Lynn/Quincy/Waltham terminals could justify full frequencies. (I would be curious of additional corridors that could justify this minimum freqency target, but the
T's market analysis suggests otherwise).
This means that for the Highland Branch, everything west of Reservior (the last BERy terminal where either the line terminates, or every other train would turnback) would be restricted to a minimum standard of 3.5 tph (which can be increased to either 4.5 tph or a max ceiling of 5.5 tph). If the Highland Branch was going to split west of Newton Highlands, that would be 1.75 tph (up to 2.25 - 2.75 tph rush hours) to Riverside or Needham Junction. I'm not so sure if the Highland Branch west of Reservior were to have 4 car trains, or 6 car trains, seen on metros (or high capacity trains like that of commuter rail), that they could justify >=7 tph of 4-6 car trains from 5am- midnight, whether that's today or in 1920.
And yeah, I think the topic remains relevant both in terms of the North South Rail Link and in terms of the continued reuse of the original ROWs. For example, I think the current capacity pinch on the Old Colony Lines makes a lot more sense when you realize that both branches of the Red Line and all three Old Colony branches were originally built and run as a single system, with all of its traffic funneled through what is now JFK/UMass. There's a reason that the (bad) idea of converting the Braintree Branch to high-freq Regional Rail looks good on paper -- it's how the system was literally designed to run, waaaaaay back when.
For the Quincy Center branch, following the BERy terminal + Lynn/Waltham/Quincy guidelines, means that the minimum 7 tph standard (maximum of 11 tph) only applies and runs to Quincy Center only. South of Quincy Center, the line would either terminate, or if every other train turned back at Quincy Ctr., it would only allow 3.5 tph (up to 5.5 tph maximum), for any fork that exists south of Quincy Center. With 4 branches south of Quincy Center, that's only going to allow 68 minute headways for all those 4 branches. If Quincy Center could pull the maximum capacity of 11 tph to Boston during rush hour of my insane "metro style network" concept, every other train looping would still only give 44 minute headways for the 4 branches.
One other thing of note: Waltham and Lynn each actually have 2 possible routings from the BERy service area to their route terminals using mainline railway ROWs. Quincy Center only has only 1 single possible routing (via Neponset). I have the option of extending either one, or both terminals, from the BERy service area to Waltham or Lynn. To get to Waltham, I can extend either the Waverley Branch or the Watertown Branch (or both). To get to Lynn, I can use the Eastern Route and/or the B & RB & L routing from Revere St.. This means that, extending both branches for each, I can theoretically allow 14 - 22 tph to extend to Lynn, and to Waltham 10.5 - 16.5 tph (the Waverley Branch has a fork, but including or abandoning the Central Mass. fork would mean a full 14 - 22 tph anyways, Watertown would send the full 7 - 11 tph to Waltham terminal since it has no fork at all).
Quincy Center, on the other hand, is stuck with only the 7 - 11 tph of a single branch. There is no second branch like that of the Waltham or Lynn terminals. Otherwise, one way to get around this limitation, is cancelling the "every other train turnback" concept for Quincy Center only, and run every single train at Quincy Center, past it and continue south, to get any meaningful service south of it. The other solution is essentially run the Quincy Center branch's 7 - 11 tph independently of the commuter/intercity rail service, which would essentially mean quad tracking to Quincy Center all the way from Boston (and north of Harrison Sq. would need 6 tracks, since 3 branches needing 7 - 11 tph would need a quad track itself; in my insane, impractical, unrealistic concept).
