PART II
If you want to take the Franklin trains off the Corridor and run them ,with the four tracks to Canton ,you could have Corridor commuter trains stop at Readville and Franklin passengers could transfer there for Back Bay, instead of going to South Station and back-tracking to the Back Bay. And Passengers on the Fairmount line could go to Readville and transfer to outbound Commuter stations on the corridor. It would open opportunities for inner city residents a two seat ride to jobs in, say, Westwood.
Not going to touch this. Completely out-of-scope for any discussion of the Forest Hills situation. (Not to say it's unworthy of discussion, just that that discussion is not the topic of this post.)
The switch where track 4 would merge with track 2 at Forest would be a high speed switch capable of higher speeds for the merging track 4 and normal speed for the express track 2. I'm ready Mr. F Line . If I were King I would tell you to make it so!
This is the part that's making heads explode, I think. This, maybe even more so than the Needham forced-severing, makes no sense whatsoever. In real-track terms you're essentially exchanging something like a couple of thousand feet of Track 4 for the equivalent length on Track 3 (which is actually probably a bad thing).
Your conception of express/local would imply that, east of PLAINS, the merged Tracks 4/2 (Track 2) would be the main eastbound running track to South Station via Ruggles and Back Bay. Track 1 would nominally be able to be used in both directions as it is today (though I think you'd need a crossover from Track 2 to Track 1 to make that possible because I
think there isn't one now.
However, because you've also force-severed Needham and apparently not provided for a Track 3 to Track 1 crossover at FOREST (in the name of express/local separational purity?) Track 3 becomes a nightmare. Anytime anything "local" (Needham or otherwise) needs to serve Forest Hills, it would (apparently) have to occupy Track 3 and only Track 3 at least as far west as PLAINS and in practice quite possibly before that (because if it was on Track 1 stopping at Ruggles, the crossover problem would be even worse than the problems from hogging Track 3. Whenever a Needham train needed to come off the branch, it would have to hog Track 3, cross over Track 1 hoping nothing needs to use it going west, then merge onto Track 2 where it hogs the eastbound lane stopping at Ruggles. Alternately you can avoid this problem by having it hog Track 3, leaving Track 1 as the westbound lane and Track 2 as the eastbound (both at least notionally branching at PLAINS)...but if you do that then absolutely nothing can move west on that track until you find some place to get it out of the way (which is at least one station stop longer away). That's demonstrably insane, hence why if the track was actually configured like that you'd have the inbound Needhams wait on the branch until there was a nice wide gap to fit them in: i.e. screw Needham for no cognizable reason.
The configuration
doesn't work. None of the changes downstream (south/west) of Forest Hills on the corridor require you to touch PLAINS in any way whatsoever. All the changes required are at FOREST, and that's simply ADDING crossovers to-and-from Track 3 to Track 1 and extending Track 3 from just being the Needham lead to also being the 4th NEC track. Your changes at FOREST are useless at best (to the extent that they prefer Track 3/the north platform track for Needham anyway) and detrimental at worst (just because they don't have Needham meets at FH now doesn't mean that the flexibility is unnecessary let alone somehow objectionable). Your changes at PLAINS are not only incomprehensible, they are outright destructive to its ability (in concert with FOREST) to handle throughput and serve as the sorting point for the NEC, and they are in no way required for the (I'd say good) goal of adding a south-side ("Track 4") platform at Forest Hills.
By-design
breaking the
current not to mention future capacity of the system for any reason - and the only one I've been able to discern is an unsupported preference for strictest-possible express/local separation -
is not a Transit Pitch, let alone a Reasonable one. Everything above the dividing line in the middle of my post is at least worthy fodder for consideration if not already things that are board-consensus things that should have been done yesterday. Everything below, unless there's a great deal more to this that you've not been able to convey, is so fundamentally outside the purpose of this thread that discussing it any further would have no purpose beyond beating a dead horse. I've never liked seeing ideas get ignored, stonewalled, or dismissed out of hand on any forum, here or elsewhere, which is part of why I've tried at length to unpack what it is you're offering, but at this point I feel like we've reached the end of the road so, respectfully, I'm out on this one.