I wonder what the odd are of any of that happening today. Only Orange to Needham and Blue to Lynn seem likely, as well as Orange to W.Rox. I would love Orange to go up to Reading, Green/new HRT to go up to Woburn (Anderson, probably not via Woburn Center), and Red to Lexington (under the trail), but these all seem like mega-pipe dreams at this point. Honestly, the most difficult build; Red to Arlington/Lexington is probably the most likely long-term as it's the only one of the 1945 Map lines without Commuter Rail, and are both growing fast enough to need better transit than at some point in the future...
The only ones that are impossible are:
1) Riverside-via-B&A, because the Pike claimed 2 of the 4 Worcester Line tracks in 1965
2) The W. Rox-Dedham trajectory, because the T let developers build houses on the Dedham ROW within the last 5 years.
3) The 1970's/SW Expressway proposal for an Orange branch to Hyde Park, Readville, and 128. No way can they take 2 of 4 NEC track berths, destroy the Neponset Reservation waterways by expanding the 3-track max NEC ROW, or kill the Fairmount with that extreme a load-sharing. Intercity is in a whole different world than it was 40 years ago.
However, they're achievable as "Fairmounted" alternates:
1) Add New Balance + Newton Corner + a Riverside turnout to the Worcester Line and upgrade the 3 single-platform Newton stops, put some nimble crossovers every couple stations so thru trains can easily pass the locals, run a Fairmount schedule. Couple fewer stops than the old plan but covers all the essentials and can be implemented SOON.
2) Reopen the former CR line from Readville to Dedham Ctr. on the landbanked/un-trailed/un-built Dedham Branch, which is completely grade-separated and well-buffered from the neighbors. Intermediate stop at East Dedham. Can be a single-track branch off the Fairmount Line, dividing service patterns between Westwood/128 and Dedham Ctr. Would require the Fairmount-Franklin connector truss bridge to be replaced with a realigned one featuring a track split. Lower-priority, but not real expensive and accomplishes approximately what the OL plan did.
3) n/a. They actually ought to eventually close Hyde Park station and let nearby Fairmount subsume all the local boardings + bus transfers if they want to keep stuff moving smoothly on the post-2025 NEC. And Westwood can easily take a Fairmount extension without congestion since there's room for an eventual easterly turnout and 5 total tracks/platforms at the station. The presence of Fairmount mitigates somewhat the need for that old OL branch.
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All the others are still feasible:
1) Blue-Lynn. They may have to go through the marsh on the Eastern Route because they once again let developer encroachers build shit too close to the ROW in Point of Pines. That's OK, though...if it's got Oak Island and West Lynn intermediate stops it's close enough.
2) Orange-W. Rox. Only the Dedham stop is blocked, and as discussed this is ultimately a high-priority one for the outer neighborhoods and because the Needham Line is choked by the NEC.
2a) Green-Needham Jct. As discussed a project dependency for cutting the Needham Line for Orange, and mega ridership on the north end.
3) Red-Arlington. Would be built per the 1970's plan as a continuation of the subway (currently ending under Thorndike Field in Arlington) through Arlington Ctr. with surface portal roughly between Water St. and Mill St. in same shallow construction as the Davis-Alewife segment. So the Minuteman would only be closed temporarily in small small segments during construction (Thorndike Field-Lake St., then Lake St.-Linwood, etc.) then put back together on top of the tunnel.
To Heights the Minuteman can easily be shifted a few feet aside at Russell Pl. and the Summer St. vicinity, then the ROW gets a bit wider and should fit both. Although there is probably going to be some remaining NIMBY resistance here, so it's better to build to Ctr. first as one distinct project...pour the whole subway, use the Ctr.-Water/Mill stub as replacement Alewife layover tracks.
Then Lexington where there would be some trade-offs with a far less picturesque trail next to the rails (i.e. looking more like the GLX Somerville path extension than the Somerville path near Davis). But this is why it's better to construct in stages. I think Arlington Ctr. needs to happen eventually because the 77 will simply be that congested in 15 years and there's only so much BRT-lite you can attempt on Mass Ave. past Harvard. But they can take it slow past there.
4) Orange-Reading. Put it this way: if the N-S Link opens and forces thru-running electrics, both Needham and Reading become odd man out on thru-running routings. Needham for obvious capacity reasons...it's just going to be too difficult to finagle thru slots with how constrained the schedules are. And Reading because you would never thru-route to Haverhill from somewhere else by going the whole Western Route. It's too painfully long and too hard to keep on-schedule. I bet all Haverhill schedules (incl. surface terminal runs) have long since reverted back to Lowell Line-Wilmington by this point like it used to be pre-1979 and Reading is back to its own Fairmounted local stub. And if that's the case the cost of constructing wholly duplicate electrification to Oak Grove is not going to be worth it and the cost differential to grade separating and going Orange starts to narrow. Plus if the Eastern Route is going to be beneficiary of thru-running (with Portsmouth probably in the mix), it needs to monopolize those extra slots in the constrained Somerville portion shared with the Western Route, which puts Reading in more of a Needham-like situation for unexpandable schedules.
5) GLX (or heavy rail substitution) to Woburn. I bet a West Medford tack-on gets some movement after Route 16 is built as the NIMBY's about-face and suddenly want their toy. If the Lowell Line is grade-separated here they're almost certainly going to provision the duck-under for 4 tracks, which will allow West Medford to flip to LRT sooner. 2030, let's say. Now...let's say by the time the state's serious about final N-S Link era you've got 1) high-frequency Lowell-Nashua local service running on a dense schedule more or less in Worcester's ballpark, 2) relocated Anderson-Haverhill expresses running at full schedule, 3) NHDOT/Concord expresses running at full schedule, and 4) a much more robust and Regionals-esque Downeaster schedule sharing all the same 90 MPH track. It can easily handle all that, but the inside-128 stops start getting squeezed when you throw a *significant* amount of NEC thru-running via the Link through there. Now you gotta think seriously about displacing Wedgemere, Winch. Ctr., whatever Woburn infill stop exists by then (Montvale Ave.?), and Mishawum if it still exists to keep all this New Hampshire thru-running moving along.
The ROW is 4 tracks wide everywhere except for the mid-1950's grade separation on the Winch. Ctr. viaduct. So there you go...pretty easy rapid transit to Anderson absorbing all local stops if the stone arch bridge over 16 is widened and West Medford's provisioned for 4-track, and if the rapid transit ducks in a short subway under the Winchester viaduct. Up the Lowell Line speed to 110-125 MPH with all trains expressing from Boston.
Don't know if this will happen, but if you're betting on the Link being as transformative to regional rail as it could be it's going to be a scenario they'll have to consider post-2040. I do not think a thru-running commuter rail system works all that well with CR here having to double-up so much 495 and interstate running with so much inside-128 local stops. We are not like SEPTA where thru-running CR only extends 20 miles in all directions from the city center at 128-like distances with dense spacing.
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I do not think Waltham via Fitchburg is ever going to work. Belmont's NIMBY's are so rich they will never warm to rapid transit, and I don't know if Red through downtown can handle another north branch if Hanscom is on the table. This might be better as a GLX-Porter tack-on. If GLX-Medford got subsumed by heavy rail there'd probably be enough capacity to fork the Union/Porter branch to Watertown and Waltham. Fitchburg is ex- 4 track through Belmont. The Central Mass from Beaver Brook to 128 can have commuter rail diverted over it to meet back up with the Fitchburg at 128, with rapid transit taking over Waltham Ctr. and Brandeis. Probably better with Green than Red given the tricky grade crossings.
But I think you've got a damn hard slog of it trying to get 2 side-by-side modes through Belmont without pearl-clutching from the rich locals. 2050 might be too optimistic for them.
Obviously you've got LRT Urban Ring potential along the Eastern Route in Chelsea. And the Grand Junction if the Link happens or if they can finagle a replacement Worcester-Fitchburg connector alongside 128 in Weston.
Orange from West Rox to 128 is very engineering-feasible, but I've written at length why it's risky until studies can PROVE the all-day ridership will be there beyond a reasonable doubt. And Orange to Needham Jct. to Green is feasible, but really really doesn't look like it would have the ridership.
Blue from Lynn to south-of-portal Salem on the Eastern Route is viable. That is a 4-track ROW the whole way and the estimated North Shore ridership is mind-blowing. I do not think you could go through the tunnel, since there definitely isn't enough room to widen it for CR and put a rapid transit berth. Subsuming Chelsea, Riverworks, Lynn, and Swampscott to rapid transit helps a lot if Portsmouth/Rockport are going to see a ton of Link thru-running. You want to get to 128 fast.
I do not think further Red extension south of Braintree is viable, despite the attractiveness of Randolph Ctr. The ridership just isn't quite high enough to jibe with the rest of the branch's boardings, and the Old Colony was never wider than 2 tracks. Ditto if you spurred to Weymouth. Little way of doing that without cannibalizing the Greenbush ROW and messing up the daily Quincy Shipyard freights. Think you gotta draw the line at 128/3 if Lexington is in-play to the north.
Fairmount will never be in-play for rapid transit conversion because of freight. Port of Southie is going to be doing a lot of container-to-rail business in 10 years, and it will never work clogging the Back Bay tunnel and Worcester Line or clogging the Old Colony all the way out to Middleboro. Fairmount-Readville-Franklin-Walpole-Framingham is the escape route that skirts the commuter rail schedule with no impacts. You COULD double-up Fairmount with Red from Mattapan south of the Neponset where there used to be so many freight sidings the ROW is a continuous 4-track width to Readville. If you were willing to subway under River St. or deep-bore Porter-Davis -style under houses to reach the ROW before the Neponset bridge. But that is probably not anyone's idea of a high-priority project unless Hyde Park looks too transit-starved by comparison after Rozzie, West Roxbury, and Mattapan get their heavy rail. Post-2040 at earliest.
