Melbourne Train Control System is running on a hardware emulated PDP11
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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.
That being said, it's pretty common in retrofits for the older system to still be around as a fallback if the CBTC fails.
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.)
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.
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
It is also, where provisions have been made, possible to put CBTC equipment on old trains. That is what NYC is doing, for example.
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_con...
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.
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.
Trains runnin have been running this way in normal passenger service for months now, though I think it’s only in the last few weeks they’ve been testing it with HCMTs entering the tunnel at Hawksburn with diesels behind them instead going to South Yarra. (Currently, the trains with actual passengers take the South Yarra route at that junction.)
The HCMTs run only on this line, from Sunbury to East Pakenham/Cranbourne. They have their own new depot at East Pakenham so they don’t have to go elsewhere for stabling and maintenance. And they probably can’t; just for them to go through the City Loop as is temporarily required that tunnel had to be resignalled (the old location wasn’t visible from the cab.)
They did run an old Comeng train through the Metro Tunnel, without any signalling, to test clearance for a track maintenance train.
It was everything you imagine a 70s era data stream to look like. 1200bps, weird control sequences, etc., etc. And no-one could really tell us much about it, but there was some poorly photocopied incomplete documentation.
There were actually two PDP-11s, the one to run the platform displays running locally-written software.
The “weird control sequences” sent between the PDP-11 and the plaform displays were HDLC, a synchronous protocol then common in IBM token ring networks as SDLC. This was actually a decent technical solution because they only had to run one coax cable down each train line and the PIDS could sit there watching for their token slot. The hardware for HDLC would have been commodity, whereas fibre optic or carrier sense for long-run packet was not.
The other PDP-11 that ran the signals (the “train describer”) could plot the position of trains on glass TTY terminals using escape sequences (VT100, same as in xterm today) so our PDP-11 pretended to be one of those and screen-scraped. So I was told, when I asked the guy who wrote it.
All of that was done before I got there. I was called in with 6 weeks to go before commissioning to fix the bit in the middle that recalculated train positions and arrival times.
Do you have a blog or somewhere else where you share tidbits of information like this? Cause I sure would love to read that.
If you are into retrocomputing, they’ll pay you to have fun doing archeology and necromancy. It’s heaven.
2.10 strangaric - legacy train control system stabilisation.pdf
https://en.m.wikipedia.org/wiki/SIMH
You can run it too.
Installing simh from "open-simh" and everything works according to instructions, I tried using the version V3.12-5 mentioned on the page https://simh.trailing-edge.com/ and this (and all 3.x?) is the "classic" simh and didn't support the referenced vax780.ini, but the version from github (4.x?) worked. Very cool to see vms boot!
The bus factor on that PDP-11 software must be uncomfortably low.
I don't think it's hell if you like retrocomputing. Personally I find it fascinating. In the past I sometimes had to work on legacy systems and I liked playing the archeologist role.
Maybe you are not referring to the platform, but rather to code quality. But I have found some a lot of jumbled messy React code in early stage startups, and some decent code in legacy systems I have worked on, so I guess code quality is not always directly related to age of the system...
To be clear, parts of it are in COBOL. Other bits are in RPG, others yet in PL/1, and then a generous application of java, c++, windows shell scripts, unix shell scripts, and it’s all held together with TSVs.
It’s more like hoarding than anything else - “don’t touch that, it might be useful, I don’t know, just leave it as it is, we’ll get eleven new servers for whatever it is that it does”
In the end we gave them a pile of python that ingested malformatted EDIs that another system made and spat out TSVs so that same system could then not trip over its own shoelaces.
I was at one of Australia's 'big four' banks. My $100m project was charged with replacing a tiny part of their mortgage system: the onboarding of a new customer. That was it: just getting a new customer in to the existing legacy system.
Oracle were the prime. They were a disgrace. Accenture had their grubby little fingers in the pie and were theoretically, laughably, going to run the thing. They used to charge us $2m to copy and paste documents. The thieves.
It was an utter shambles. The 'plan on a page' was diamond shapes on a PowerPoint slide. There was no link to any sort of reality.
I lasted 9 months before the blessed gods let me go. Shortly thereafter the whole thing was cancelled.
I think I may have actually been working on the project you are talking about from the Oracle side. I think many of us tried our very best as individuals.
I was never on it full-time, I worked for Oracle engineering but they'd sometimes send us on-site at big customers to fix problems when they blew up. It can be a lot easier to debug a customer's problem when you have the source code right in front of you.
https://www.vice.com/en/article/the-cartel-supercomputer-of-...