Re: Boston to Cape rail
The Southeast Expressway is going to need to be overhauled eventually and addressing the abutting transit tracks (e.g. the Dorchester track crunch) will need to happen as a part of that project no matter what.
The real question is whether you can restructure the Red Line tracks. There's no room for a second or third commuter rail track between the point where the Red Line emerges and the point where its two branches diverge. South of the split there's a short stretch of single track that should be fairly easily double-tracked if money's available. Double track already exists (although it might need realigning) as far south as North Quincy, and there's room for an extremely long passing siding south of Wollaston to just north of Quincy Center.
Quincy is a bigger problem than Dorchester for finding the width. I don't think there's any solve for the Wollaston pinch. As for Dorchester...it's pricey, but straightforward. The only thing they have to avoid is the stupid, stupid, stupid "reimagining the SE Expressway" renderings that call for outright HOV lane capacity expansion at Savin Hill and a convoluted Wellington-style tunnel that buries both the Braintree Branch and the Old Colony for a stretch so the highway can get hugely wider. That's a billion-dollar project that's completely unnecessary.
If they kept it simple it could be done by:
1) Reconfiguring Columbia Jct. to be less spread-out. I drew this crude rendering some time back of how to compact the whole works while retaining all of the present-day 4-track grade separation:
-- The JFK platform is designed as an island so you can just drop the second commuter rail track there as-is by reconfiguring the Red headhouse and taking the inner busway.
-- Instead of the umpteen track splits sorting out inbound/outbound onto the separate islands (making JFK platform assignments really confusing), do a simpler 1 island for inbounds, 1 island for outbounds. That greatly compacts the track layout because you just fork or merge at a crossover near the subway portal to pick branches, and flank the outside of the portal to get to/from the yard. This is what buys the space to continue the Old Colony double-tracking the full distance to South Station.
2) Now...notice on the left of that drawing. Braintree gets buried under Ashmont in a shallow box tunnel immediately south of JFK station. Since the Ashmont IB/OB tracks flank the outside of our new track layout, there's no need for those space-intensive flyover ramps. Braintree just takes the middle and Ashmont spreads out around the portal the same way the yard tracks flank the current subway portal.
-- The bare roof of the tunnel becomes Ashmont's literal trackbed, so it's more of an air rights thing than a subway. It allows for consolidation of the electrical and signaling utilities for both branches, since they currently duplicate themselves 100% of the way to the Clayton St. split. Makes the whole Red Line easier to maintain.
-- Old Colony takes the current Braintree OB track berth for its second track. Braintree IB track gets given over to I-93 for widening the breakdown lane. Tracks can be compacted a little closer together than today because you no longer have Braintree Branch utility boxes and cable conduits eating up a couple feet's space next to the highway.
-- At Savin Hill station the tunnel swings under the OC tracks to avoid the station foundation.
-- Portal-up on Braintree's current alignment just as 93 starts peeling away.
-- Swing the Ashmont tracks a few feet west to create room for +1 track berths on the Freeport St. overpass.
-- Add +1 track berths to the Park St. overpass.
Now the OC is contiguously double-tracked from SS to Wollaston. It's expensive, but it's not billion-dollar expensive like the I-93 HOV lane expansion insanity. So if MassHighway is going to be a significant stakeholder in this they're the ones who have to behave themselves. The T just has to look at this as forward-thinking: they greatly simplify the Red Line infrastructure at zero loss of capacity and make their 50-year maint costs go way down, while gaining that 2-track commuter rail capacity. It doesn't even require a rebuild of JFK station itself...you're just swapping what direction the tracks originate from by culling all that flyover nonsense on both sides, and then doing the box tunnel next to the highway.
Now, I don't think you're ever going to get unbroken double-track all the way down to Braintree, at least not without the kind of investment that a million other places are going to want and deserve far more than here. You can certainly get it for most of the run, but not for all of it.
Only other places it's really doable are minor. For example, the Braintree Split reconfig on Route 3 is going to nuke/rebuild a couple bridges downwind of the interchange for the new lane arrangement. Right now the line gets pinched to 1 track at the freight yard where it passes under those bridges. So MassHighway will probably do all the work of getting the DT modestly extended from the freight yard north to the junction with the Greenbush Line. Possibly even as far as when the OC starts descending into that duck-under of the Red Line past Washington St. That won't be much, but it'll allow Middleboros and Plymouths to pack real close behind a Greenbush, and then if you double-up JFK (which is not dependent on doing anything in Dorchester...just taking the busway and reconfiguring the Red entrance) pass the Greenbush on the platform. Essentially turning any Greenbush slot into one where a M'boro or Plymouth can come either direction 2 minutes later and overtake.
I still don't know how you're ever getting contiguous DT through Quincy. Though if you did the painful digging at QC station to double-up that one you probably get the biggest gain overall by letting Plymouths and Greenbushes pass Middleboros. And then add the Dorchester fix and it's probably enough overall to satisfy Cape and Plymouth growth for a good long time. Don't forget, they were thinking a Big Quincy + Dot Dig was going to be necessary if Fall River/New Bedford were crammed down the Old Colony. That's not going to happen, so for just Cape + Plymouth + Greenbush you'll probably never need to fix Quincy...just do everything north of the river, fix QC station, and don't get any crazy ideas of Indigo-ing these routes anywhere except maybe stepping up short-turn service to Brockton.
Unfortunately, that leads us into a question of whether it's worth it to have two tracks through JFK/UMass - a question to which the answer might unfortunately be no, since the biggest reason to do it would be if you had a real shot at a complete second track all the way down (you don't) and at least one of the four Red Line tracks running through there right now would need to go away to make room for the second commuter track. (Go away in this context could mean burying the Braintree Branch underneath the Ashmont branch. It could also mean busting JFK down to two tracks and building a flyover junction at Savin Hill, which is of dubious merit and probably unreasonably expensive.)
See above. You *do* gain some rush hour slots at JFK by being able to have M'boros and Plymouths ride right on the ass of a Greenbush then blast right by while the Greenbush is making a station stop. That's worth the extra slot or two per peak for re-balancing an M'boro schedule for Cape service. And it's cheap. I'm honestly surprised there's been zero movement on that because it's such an easy fix.
