The basic design would be CBTC. Which can either have moving blocks or fixed blocks. Since the blocks are mostly software-based and virtual, it can be whatever you program it to be. Moving blocks probably are not going to work in the Central Subway, so they would have to implement it with fixed blocks more or less the same as the current setup. And surgically fine-tuned to not decay headways under computer guidance vs. line-of-sight/human judgement. That's hard. Not impossible, but really really hard. And they have to get it right on the first try, so they can't proceed with haste.Oh, I was making a list for the entire Green Line, not just the "B". And my understanding is that the Type 9 design and order is being funded through the GLX, at least, enough for the new branches to use.
This is somewhat of a "transit pitch" but if they got the money somehow, where to put it for best effect?
- POP infrastructure (ticket/vending/validation machines)
- Power system upgrades to central subway
- Add more Type 9 cars to order
- Traffic signal upgrades where needed
- Fund design and study of modern signalling system in central subway
- Reconstruction of BU Bridge/Comm Ave intersection (in conjunction with MassHighway)
- Reconstruction of Packard-Warren (centering ROW)
On the topic of CBTC, my understanding is that computer-based moving block safety systems can achieve upwards of 36 TPH, maybe more in practice (and in theory). The GL is currently scheduled for nearly 48 TPH on the most central section. But GL vehicles are much easier to stop than most other railroad vehicles. Does this really require a whole new design, or is it just an incremental improvement to existing ones?
IF such a setup can be designed it wouldn't increase throughput, but would bring all the other compelling advantages advantages of CBTC: safer operation with auto stop enforcement, vastly less track-mounted hardware to maintain, far less reliance on human dispatching. But, again, Central Subway capacity isn't the issue so much as unpredictability of branch schedules causing clogs where they intermix. So half the battle of making it run smoother is getting the branches all reliably on-schedule. Fix the surface clogs on the B and C first. Then a more conventional CBTC setup on the D and GLX to manage those headways. At a purely traffic management level the Central Subway can thrive as-is if the pen-and-pad guesswork were reduced to just the Kenmore-North Station stretch with more accurate branch arrival times. After all, it handled many more branches than this a half-century ago and lots of 3-car operation back then too. The main argument for CBTC downtown is purely safety: preventing operator-error incidents like the Gov't Ctr. crash. With secondary considerations for lowering maintenance burden and preventing crippling signal downtime like there was for months after the '96 flood shorted out everything from Kenmore to Copley. All of that's worthwhile enough to keep plugging away at the studies for due diligence.
Type 9's have a +30 car option order to the 24-car base order. So there already is pretty generous flex for piling up enough cars to initiate all-day 4-car ops on the subway, D, and GLX co-mingled with all-day triplets on the B, C, and E.