Brattle Loop
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- Joined
- Apr 28, 2020
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Re Needham: @Brattle Loop, I'm not sure that what I have in store will cover that much new ground for you, I think we discussed it relatively recently. But I'm hoping to pull together something that balances being comprehensive and concise, have everything in one place.
The Needham discussion comes up enough that just having one comprehensive overview in one place would be an enormous asset in and of itself. At the moment the discussion here is fractured between a few different threads (unsurprising, given the different elements that would go into Needham replacement, but it does make more work trying to dig up answers to questions).
@Brattle Loop walked through a number of the challenges that Blue-under-Huntington would entail, and I second everything he (?) has said. I have a much more detailed piece in the works about my vision (well, ideas at least -- perhaps shouldn't call it a "vision" and overhype it!) for Boston's LRT, and a lot of it builds on the examples Brattle Loop gave.
Thanks for that. I wasn't quite willing to dig through the depths of the Green Line Reconfiguration thread at that hour of the night so I was hoping I hadn't made any egregious errors, so I'm glad that I got the gist of it right. (And, yes, "he" is the correct pronoun.)
Re automated light metro: yeah I agree, there's no hope until the Central Subway has a modern signal system. Automation also basically requires a "fully sealed" ROW, with basically no grade crossings -- I find it impossible to imagine the B, C or E being automated. That also, in my opinion, would preclude any subway that the surface lines run into -- my impression is that intermingling automated and human drivers is either infeasible or gives you the worst of both worlds.
Yeah, the only way the Green Line as it currently exists could be automated is with a combination of full automated train control (not in and of itself all that difficult in a vacuum, but grafting it onto a 115-odd year old light rail subway wouldn't be cheap) and something not unlike full (or nearly full) self-driving car technology, to deal with the traffic crossings (and pedestrian crossings) on the surface branches. That second prong's a massive ask for a technology that doesn't even work yet in its intended market.
I suspect it'd be theoretically possible to mix automated and human-operated (or, rather, semi-automated) vehicles if the system was designed well. At least some ATC systems I know of basically layer train protection and train operation, and can run (sometimes not as well) with manual operation (but still automatic protection/separation), and it's probably at least possible to design it so that some vehicles are automatic-operation and some are manual (though probably with a performance hit to account for more variables). That said, the surface branches would still have to have human operators, and that's a good number of runs, meaning that the staff reductions that would be a benefit of automation wouldn't be as big of a benefit. I don't know that I agree that you'd wind up with the worst of both worlds, I just don't see what the point would be (unless one's coming at it from a purely anti-union approach, in which case it would make sense even if I don't think it'd be a good idea or good value).
If you built a full Huntington subway, connected it to Brookline Village at one end, and ran it along the commuter rail ROWs into South Station and then through the Piers Transitway -- I suppose that could form a fully sealed ROW, though a branch to Needham would put you on the rocks again.
As in not linking it to the Tremont tunnels? Apart from the extreme difficulty of getting into the Transitway from anywhere but Essex (I do not have the energy to go digging for F-Line's deeply pessimistic detailing of the issues with trying to access that thing from Atlantic, it's around somewhere in one of these threads), cutting off the downtown access and the Blue Line transfer is a steep price to pay for a sealed ROW, especially when doing it as unsealed LRT means you could run into the Tremont tunnels or to the Seaport via the Transitway, which adds capacity and route options to the LRT network. (Needham does indeed introduce even more chaos.) I think this is an area where the "lesser" solution on paper (LRT) is actually the better option.
If the T wants to invest in automation, I'd rather see the Red, Orange, or Blue Lines, where precise acceleration and deceleration can allow you to squeeze a few more trains into the subway. But even there, I think we're a long way off from it being worth it.
Design the new signaling system they're supposed to be getting properly and it makes it a hell of a lot easier to graft automatic operation on top of it. We'd get significant benefits from CBTC/moving blocks as the standard even with human operators anyway, and it's not a giant leap from that tech to full-automatic operation (though we might need some door-related behavioral modification if we're ever to get the computers in charge of the doors )