Just to throw my 2 cents in on most of the transit maps I see here (cause I'm too lazy/don't really no where to start to make my own)...
In my opinion any line that comes together and then branches out should share the same color, with the separate branches receiving different letter/number designations. For instance, asap's burgundy line, I feel should just be another branch of the red line, and each branch be given a number or letter designation. ABC is already used on the greenline, otherwise that'd be perfect for the red line, A-Ashmont B-Braintree, so I'll go with numbers. 1-is maybe alewife/Braintree 2-is Ashmont/Chelsea or wherever the terminus might be.
My other thought is, if we continue to add branches to lines, we're going to see a bottle neck, there is only so many trains you can run through a single track station. Is there any reasonably feasible way to increase the size of the existing tunnel system? I just don't really know what's down there. I know that even if it's geologically possible it is possibly massively cost prohibitive. I'm not suggesting new bores, cause that's already been shot down, but is it possible to increase the size of the tunnels we have?Ideally I think it would be good to see 2 tracks in each direction? I think it adds flexibility to the system that would be very beneficial.
TL/DR for that part: Is it at all possible/reasonably feasible for us to expand on the underground network, or are we just stuck with what we got?
We don't have the options of widening tunnels for express tracks like NYC.
-- New York's system has had that feature since very early on in its existence. We haven't. Our 4 trunklines were built through downtown when the surrounding density was far lower, particularly in Back Bay when the landfilling of the Charles Basin was only a few decades old. A century-plus worth of development has locked the tunnels into their existing footprint.
-- Same geological challenges to widening as there is to building new tunnels. The glacial and landfill mush is extremely arduous and expensive to tunnel through and support without unforeseen impacts to surrounding structures (e.g. Copley elevator syndrome). Moving a load-bearing tunnel wall is almost as fraught with peril as building a whole new tunnel on some different street. Note with NYC: Manhattan's built on as rock-hard a slab of bedrock as you'll find on the East Coast, so they don't have nearly as tough a time.
-- Street grid. Narrow, winding vs. wide and in coherent grid in NYC. This is what sent Silver Line Phase III off the cliff: a wider BRT tunnel on a narrow street. Start contemplating that on 2-track subway tunnels to make them 3- or 4-track and the same constraints start driving the cost to the moon.
-- It's arguable we still don't need it. The Red Line is still not in the same universe as the Lexington Ave. subway and several others in NYC. Not even close. There are considerable improvements to tap on the 3 heavy rail lines simply by giving them modern signaling, tighter headways, and simply more cars. Orange is running far below capacity because it still has the same car fleet that ran 4-car trains through several fewer stops on the Washington St. El; we're 32 years into a fleet shortage, and that's the only thing preventing tighter headways. Red used to pack 'em tighter tighter until its 1988 resignaling spaced out the downtown blocks too far; creeping speed restrictions and increased dwell times from exploding Park-SS ridership has decayed it further. That ceiling can be lifted a lot on the existing track.
Also...every study that slams the T says lack of adequate radial circulation around downtown is what's harming the existing lines, not inherent capacity of the trunks themselves. Those are all the 2030+ doomsday warnings about when transit bottlenecks start inhibiting the Boston economy. So there really is no way of avoiding Red-Blue to load-spread the inter-line transfers away from the Big 4 downtown transfer stops. There's really no way of avoiding completing the Transitway-Back Bay link to load-spread away from Red and Orange @ SS + DTX, and if Silver Line Phase III just can't be built they have to go back to the drawing board and solve this. There's really no way of avoiding the Urban Ring in some permutation. There's really no way of avoiding finishing the job on the Crosstown Bus system and giving Boston a robust network of express buses. There's really no way of avoiding better rapid transit, DMU/EMU, and express bus links to the most critical bus terminals (Dudley and Lynn being the most acute cases).
There's not a whole lot more to say there. The needs can't be put any more starkly. The only thing to debate is which projects need to go first. Then it's simply a matter of breaking out of this trance the state is in, reform the T and give it the resources it needs to survive, and git 'r dun on these projects before it's too late...and without shooting themselves in the foot on senseless waste or half-completions.
As for where tunneling is possible, it's not with widenings on the existing trunks. It's confined to ROW's where there's pre-cleared land.
-- Urban renewal zones that were wiped clean in the 60's and have well-documented underground utilities, generally wider/widened streets from their makeovers in the peak-car era, and more modern abutting structures less likely to suffer Copley Elevator Syndrome like the old churches on Boylston.
Examples would be: South End trajectory off the abandoned Tremont St. Green Line tunnel hugging the Pike to reach the Transitway or portal-up for Washington St. light rail. Or Red-Blue where the West End makeover and ultra-widening of Cambridge St. 70 years ago makes one side of the street far easier and less invasive to mitigate. All of them have individual challenges to solve at single points along the way, but they are nowhere near the daunting minefield that the SL Phase III dig under Chinatown would've been.
-- Underneath existing active ROW's. The B and E reservations, for example. Well-buffered from surrounding structures, doesn't require much road traffic disruption to build, and they have been in use for so long (in the inner B's case, uninterrupted service since 1892) that there was never enough opportunity to string enough undocumented spaghetti utilities underneath. Or under RR tracks and RR terminals, like the North-South Link lead tunnels would go with minimal disruption under the NEC and maze of yard tracks at South Station and North Station. Likewise with the Link...underneath the pre-cleared Big Dig space below I-93. And yes, that is a viable rapid transit ROW if the ultimate build decision sides with 2 x 2 RR + rapid transit tracks instead of 4 RR tracks or just 2 RR tracks alone. Or...if Storrow Dr. is ripe for a downgrade or elimination, a Riverbank subway from Charles to Kenmore (Blue) at very shallow depth on one of the carriageways' roadpack.
-- *Short* infills, where the pain of under-street tunneling is confined. For example, if the E gets buried to Brigham Circle with non-disruptive tunneling under the reservation, ripping up Huntington to complete the distance to Riverway and Brookline Village is not prohibitively hard or expensive (helps also that the surrounding buildings are not too tall). Or Red-Blue where the mitigation to the Beacon Hill side is only a few blocks total.
You can easily see how Green benefits the most from all this by stringing together--in stages--the makings of parallel trunks: the Urban Ring route along the Grand Junction in Cambridge between BU Bridge and Lechmere; the Transitway link through the South End along 60's-nuked highway land; staged burial of Huntington taking downtown load off the Central Subway.
Red could possibly get it too if the ultimate N-S Link configuration leans towards half-and-half RR + rapid transit. Columbia Jct. and JFK sets up an "X" where no two diverging trains will ever cross, so Braintree-Alewife, Braintree-North Station+ (could continue north to Medford if GLX flipped to heavy rail), Ashmont-Alewife, Ashmont-NS+ can all run in any alternating configuration with all 4 legs of the "X" having identical headways to the current downtown RL.
Now...before I get attacked for this yet again by folks who cherry-pick threads only for semantic ammo
rolleyes
...of course you have to study. Of course you have to ID what needs these serve. Of course an engineering assessment can make them no-go's. And of course you probably can't do it all. But if you want a starting point on what study
areas to focus on for reimagining downtown transit...these are the scenarios that are paths of least resistance and which have the fewest individual points of failure. They happen to match up pretty well with the radial circulation needs, too. So instead of pushing that boulder up too steep a hill pondering things like rip-up/rebuild widenings of the subways or digs of the sort of exponential complexity that killed Silver Line Phase III...use these paths of least resistance as an organizing principle for your brainstorming. We've got a lot of possibilities to chew on. It just isn't realistic to expect straight, pretty under-street lines on a map from anywhere to anywhere. The contours of the built-up infrastructure shape the transit, not the other way around.
