by F-line to Dudley via Park
Gerry6309 wrote:You could theoretically do both RR and rapid transit since the space under I-93 is set up for 2 bores of 2 tracks each. Setting aside fact that feasibility hasn't been studied, here's some brainfood for thought. . .highgreen215 wrote:It was my understanding that when the Big Dig was constructed the vertical supports were sunk much further down than required for the vehicle tunnel. It was said this was done to accommodate a possible North-South rail tunnel directly beneath the vehicle tunnels. It would seem, then, that except for the inclines at either end, the route of the NSRL has essentially been determined all ready and this portion of the basic engineering and construction has already been funded through the Big Dig. So why waste that effort if it gives us a head start to providing superior rail service through Boston by connecting the northern suburbs and cities as far as Portland and beyond (and eventually New Hampshire, Vermont and Montreal) with EVERYTHING south of Boston.Here is another way to utilize that earlier effort: Put a subway down there with a yard and shop at the Charlestown end. Use the existing fare controls at South and North Stations, with a passageway between the highway and the rail tunnels to access an island platform via stairs and escalators. At the North Station end a 5% ramp to the surface and an extension to the Monsanto memorial casino by way of the old RT line between Sullivan and Everett. That issue will need to be addressed in any event, assuming that the casino ever gets built itself.
It would be a Boston version of London's Waterloo And City Line.
On the RR mode:
-- RR Link would go from 4 tracks to 2, but they'd be in the same bore so unlike the pair of North River single-track tubes from Penn Station this would have more flexible redundancy in the form of frequent crossovers despite the capacity reduction.
-- Probably would need to cut Central Station, but Central Station was a dodgy prospect to begin with.
-- Routings through the tunnel would be a little more strictly rationed to the NEC<-->NH Main, B&A<-->Eastern Route primaries that would carry the bulk of the traffic and hit all the regional intercity destinations. Fitchburg, Franklin, Fairmount, Old Colony would probably be rationed a lot more miserly for tunnel slots, and branchlines would probably stay exclusively on-surface unless a particularly high-demand pairing merited some token tunnel slots. Keep in mind based on what Penn handles that 2 tunnel tracks is still a hell of a lot of new capacity and the frequency surge in being able to pick-and-choose tunnel vs. expanded surface terminals still affords mind-boggling service increases.
-- You would probably need to move aggressively to convert the Needham Line to an Orange extension Forest Hills-West Roxbury and Green extension Newton Highlands-Needham Junction. And to finish the Orange-Reading extension with thru Haverhill trains going back to the NH Main. It'll be a lot easier to portion out tunnel slots to the higher-capacity mainlines by expunging these two capacity-pinched lines entirely from the commuter rail system and over to rapid transit where they should've been all along.
On the rapid transit mode:
-- 2 tracks in the other bore on the other side of the wall from the RR bore. Do a low-profile "Aquarium Under" island platform on the HRT side, and plop the North Station platforms on top of the Orange level so both floors are mirror images of each other.
-- Easiest available rapid transit hookup would be the Red Line Cabot Yard leads where Columbia Jct. can act as a grade-separated "X" for pairing off and mixing 2 north/subway branches and the existing southern branches all at equal capacity. You could run Alewife-Braintree, North Station-Ashmont, Alewife-Ashmont, North Station-Braintree switching off every other run, and have the current branches bump up to frequencies equal to the present subway mainline because of Columbia Jct.'s grade separation. Huge capacity increase. I think this is cheaper, easier construction, and higher-upside than taking a branch off Orange or something that could conceivably harm downtown headways.
-- I guess you could portal-under into the Link approach tunnel right before the Cabot leads fan out into the yard, right around the South Boston Haul Road overpass. Maybe even incorporate a "Broadway Upper" station by re-using some of the Red-dimension trolley tunnel before going off-alignment into a Link-approach tunnel on the Foundry St. end. Seeing as how Broadway is a potential Urban Ring stop it might be a good idea to have both downtown subways on the "X" hit that one on separate floors along with SS while the North Station route skips over Andrew on its surface alignment.
-- Incline into the depths of the Link tunnel can be much steeper and sharper at HRT grades, so it may be cost-neutral or slightly less expensive to do a 2-track RR incline and 2-track HRT incline instead of a double-wide RR incline. Tasty enough to maybe be worth a future study if little else.
-- Double-up the Orange Charlestown portal and pick one side of the Orange tracks to spit out on that leaves the most utility intact for a future line extension. Stub-end yard on the surface, tucked alongside the Orange main wherever it'll fit. Probably don't need anything more elaborate than an Alewife Yard-style 3-tracker on compact footprint.
-- If costs need to be shaved from the RR Link, doing the rapid transit half gives all Old Colony riders FOUR transfer stops to get on a Red train signed for North Station: Braintree, Quincy Ctr., JFK, or South Station. You could cut the OC portal entirely from the RR build and make them use these staggered Red transfers. Middleboro to Hyannis would still be accessible through the tunnel by the Stoughton main to Taunton and the Middleboro Secondary to Middleboro, so only Greenbush, Plymouth, and Holbrook/Randolph-to-Bridgewater riders would be inconvenienced by a two-seater to get north. Would punish Fairmount riders a little unfairly since they'd also have to transfer at SS to get north, but I guess you could make that a little more worth their while if Red went all the way to Mattapan down the street from Blue Hill Ave. station and more or less framed each end of Dorchester.
-- Future northward extension possibilities can literally go anywhere. Any of the northside mainlines would be accessible from that stub-end yard with the right combo of duck-unders of commuter rail tracks. If you think GLX-Medford has enough 30-year ridership growth in it to fill 6-car heavy rail trains...all it would take is a duck-under and running along the south property line of BET to absorb that branch. Trolleys would continue going to Union Sq. and would have the freed-up slack capacity to take on Urban Ring LRT traffic off the Grand Junction and from Chelsea. You could sit on that stub and debate accordingly for years where it's best to go next, because it enables going anywhere next.
And if that's too much to swallow...you don't have to build both bores of the Link at once. It can be 2 RR tracks to start and an empty concrete shell on the other side of the wall that gets finished when Tracks 3 and 4 are added or when they study whether +2 RR tracks or 2 HRT tracks are the better use for the space.
