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At least in other systems the way this works is that any train using CBTC going onto a non-CBTC section will just operate using non-CBTC. Which is fine for lowe

At least in other systems the way this works is that any train using CBTC going onto a non-CBTC section will just operate using non-CBTC. Which is fine for lower frequency branches or emergency diversions. All you need for non-CBTC operation is a driver who can see. It is also, where provisions have been made, possible to put CBTC equipment on old trains. That is what NYC is doing, for example.

skissane 2y ago
> All you need for non-CBTC operation is a driver who can see. Wikipedia's article on CBTC [0] seems to want to limit the term to moving block systems only, not including fixed block – I'm not sure if that is correct or if that is just some agenda some Wikipedia editor has. But it seems to me that even in a fixed block system, the train could operate (semi-automatically) if it knew its location and the location and current state of signals – and the current signal state could be broadcast to it via radio. Would you call such a system CBTC or not? Also, it seems to me that fixed block with physical signals and moving block CBTC could coexist on the same line. Moving block CBTC trains are authorised to disregard red signals, and instead get their movement authority via radio; fixed block trains are not. If a fixed block train is in a fixed block, that locks the block out for all trains (both fixed and moving); if a moving block train is in a fixed block, that locks the block out for all fixed block trains; but two moving block trains can coexist in the same fixed block provided their moving blocks are non-overlapping. [0] https://en.wikipedia.org/wiki/Communications-based_train_control https://en.wikipedia.org/wiki/Communications-based_train_con...
- bobthepanda 2y ago
  CBTC is moving block because it just obviates the need for fixed block wayside equipment. Fixed block signalling just detects if a track segment is occupied, but in CBTC the trains can directly talk to each other, at which point blocks are superflous. Both types of systems can be automated. And yes they do often coexist, like i mentioned in my grandparent comment. But brand new rail lines that install CBTC often don’t, to simplify maintenance; trackside equipment gets exposed to pretty hard operating conditions and can’t be fixed without some kind of shutdown of the rail line.
  - rexpress 2y ago
    In almost every CBTC system trains communicate with a central zone controller and do not interact directly with each other. Urbalis Fluence works as you describe, but that is a very new approach to CBTC and as far as I'm aware has only one installation.

skissane 2y ago

> All you need for non-CBTC operation is a driver who can see. Wikipedia's article on CBTC [0] seems to want to limit the term to moving block systems only, not including fixed block – I'm not sure if that is correct or if that is just some agenda some Wikipedia editor has. But it seems to me that even in a fixed block system, the train could operate (semi-automatically) if it knew its location and the location and current state of signals – and the current signal state could be broadcast to it via radio. Would you call such a system CBTC or not? Also, it seems to me that fixed block with physical signals and moving block CBTC could coexist on the same line. Moving block CBTC trains are authorised to disregard red signals, and instead get their movement authority via radio; fixed block trains are not. If a fixed block train is in a fixed block, that locks the block out for all trains (both fixed and moving); if a moving block train is in a fixed block, that locks the block out for all fixed block trains; but two moving block trains can coexist in the same fixed block provided their moving blocks are non-overlapping. [0] https://en.wikipedia.org/wiki/Communications-based_train_control https://en.wikipedia.org/wiki/Communications-based_train_con...

bobthepanda 2y ago
CBTC is moving block because it just obviates the need for fixed block wayside equipment. Fixed block signalling just detects if a track segment is occupied, but in CBTC the trains can directly talk to each other, at which point blocks are superflous. Both types of systems can be automated. And yes they do often coexist, like i mentioned in my grandparent comment. But brand new rail lines that install CBTC often don’t, to simplify maintenance; trackside equipment gets exposed to pretty hard operating conditions and can’t be fixed without some kind of shutdown of the rail line.
- rexpress 2y ago
  In almost every CBTC system trains communicate with a central zone controller and do not interact directly with each other. Urbalis Fluence works as you describe, but that is a very new approach to CBTC and as far as I'm aware has only one installation.