4 ms·

Apparently, this is no longer the case, and the old emulated PDP-11 system was replaced with a new system in 2014–2016: https://news.ycombinator.com/item?id=291

Apparently, this is no longer the case, and the old emulated PDP-11 system was replaced with a new system in 2014–2016: https://news.ycombinator.com/item?id=29157259 https://news.ycombinator.com/item?id=29157259 The old system we are talking about here was Ericsson JZA 715, mostly written in Pascal with some parts in PDP-11 assembly, running under RSX-11M. Melbourne was the first site in the Southern Hemisphere for Ericsson's JZA series train control software, going live in 1982. JZA 715 first went live in Oslo in 1979. Earlier iterations of Ericsson's JZA software (JZA 410) went live in Stockholm in 1971 and Copenhagen in 1972.

bobthepanda 2y ago
There is also an even newer CBTC system going into use for the new metro tunnel.
- rbanffy 2y ago
  I wonder how much of that code is the old code compiled for the new platform.
  - bobthepanda 2y ago
    As part of the new system, I don't think very much at all, since the two technologies are fundamentally different; CBTC is trains talking directly to each other, and cab/wayside signalling is the tracks telling the trains what to do. That being said, it's pretty common in retrofits for the older system to still be around as a fallback if the CBTC fails.
    - skissane 2y ago
      The Melbourne Metro is just a new tunnel on existing lines, so I would guess they are going to have to support some kind of interoperation between CBTC and non-CBTC? I mean, the ability to run CBTC trains on non-CBTC track or vice versa? This is different from Sydney, where the Metro lines are physically disconnected from the traditional rail lines. (Apparently there is still some track linking the Northwest metro line to the Main Northern line underneath Epping station, legacy of the old Epping-Chatswood Rail Link, but it is blocked with off with stops; there is no plan for any rail connection between the new Metro West line and the traditional rail network, despite the fact that remnants of the old Carlingford line are directly adjacent to the site of the new Metro West maintenance facility, meaning they could create such a connection if they wanted to.)
      - RossBencina 2y ago
        I'm not sure that they are going to run non-CBTC trains through the new tunnel. I have heard it said that the level crossing removal program is associated with a goal of moving to driverless trains network-wide. Presumably there is a network-wide CBTC migration plan.
        skissane 2y ago
        > I'm not sure that they are going to run non-CBTC trains through the new tunnel. The old trains wouldn’t work with the platform doors, so no. But the other way around: those lines continue beyond the tunnels on the surface, and some of those surface sections may be shared by both old and new trains, which would require some form of interoperability between CBTC and non-CBTC, until they move the whole network to CBTC. Also, I would expect that maintenance trains (track inspection, etc) will likely be shared between CBTC and non-CBTC and so have to support both
      - bobthepanda 2y ago
        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

There is also an even newer CBTC system going into use for the new metro tunnel.

rbanffy 2y ago
I wonder how much of that code is the old code compiled for the new platform.
- bobthepanda 2y ago
  As part of the new system, I don't think very much at all, since the two technologies are fundamentally different; CBTC is trains talking directly to each other, and cab/wayside signalling is the tracks telling the trains what to do. That being said, it's pretty common in retrofits for the older system to still be around as a fallback if the CBTC fails.
  - skissane 2y ago
    The Melbourne Metro is just a new tunnel on existing lines, so I would guess they are going to have to support some kind of interoperation between CBTC and non-CBTC? I mean, the ability to run CBTC trains on non-CBTC track or vice versa? This is different from Sydney, where the Metro lines are physically disconnected from the traditional rail lines. (Apparently there is still some track linking the Northwest metro line to the Main Northern line underneath Epping station, legacy of the old Epping-Chatswood Rail Link, but it is blocked with off with stops; there is no plan for any rail connection between the new Metro West line and the traditional rail network, despite the fact that remnants of the old Carlingford line are directly adjacent to the site of the new Metro West maintenance facility, meaning they could create such a connection if they wanted to.)
    - RossBencina 2y ago
      I'm not sure that they are going to run non-CBTC trains through the new tunnel. I have heard it said that the level crossing removal program is associated with a goal of moving to driverless trains network-wide. Presumably there is a network-wide CBTC migration plan.
      - skissane 2y ago
        > I'm not sure that they are going to run non-CBTC trains through the new tunnel. The old trains wouldn’t work with the platform doors, so no. But the other way around: those lines continue beyond the tunnels on the surface, and some of those surface sections may be shared by both old and new trains, which would require some form of interoperability between CBTC and non-CBTC, until they move the whole network to CBTC. Also, I would expect that maintenance trains (track inspection, etc) will likely be shared between CBTC and non-CBTC and so have to support both
    - bobthepanda 2y ago
      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...