SimSig: Railway Signalling Simulations

My favorite simulator for railway signals is NXSYS.[1] This simulates General Railway Signal's NX system down to the relay level. NX had the first "intelligent user interface" device. When a train enters the interlocking, the dispatcher pushes an entry button to indicate they want to dispatch that train. All the possible exit points then light up. The dispatcher then pushes the button at the appropriate exit light, and all the signals and switches are set up for that route.

Routing within the interlocking is automatic. Exit lights only light up if there's an available path. The system is aware of trains in the interlocking, switches locked for maintenance, and the actual position of switches, signals, and train stop devices. As a train moves through the interlocking, track space and switches are released behind it automatically, becoming available for other trains.

Today this seems routine, but it was a huge breakthrough in the 1930s. The original marketing brochure is available online.[2]

[1] https://bernardgreenberg.com/Subway/

[2] https://anyflip.com/lbes/vczg

This is really cool!

For people who don't want to go full scale sim and prefer a bit of a lighter interpretation of working with signalling screens, I can recommend Rail Route (https://store.steampowered.com/app/1124180/Rail_Route/).

first paragraph on home page is really funny and alluring : "... How often has your train been delayed because of "signal failure" and you've wondered why trains can't be routed around the problem - or why it is even a problem in the first place? You'll soon see exactly why - with SimSig!"

really resonates with my experience as a commuter

While we're on the topic of niche railway games, I highly recommend [NIMBY Rails](https://store.steampowered.com/app/1134710/NIMBY_Rails/) - it is the closest you can get to building functional railway systems in a game.

Memories of playing Heathrow Air Traffic Control (https://www.spectrumcomputing.co.uk/entry/2270/ZX-Spectrum/H...)

For German speakers: https://www.estw-simulator.de/index.html https://www.estwsim.de/cms/index.php

These have been around for a while and quite closely mimic (slightly older) German signalling specifications for signaller interfaces.

My company builds such systems as test and demonstration systems for real railway projects with respective functional safety constraints. If you're interested to learn more about the signalling infrastructure in Europe or Germany, feel free to ask.

Railway signalling IMO is an area where a little research could dramatically increase the throughput of the railway network with a rather low cost.

Todays railways mostly use fixed block signalling. Expensive and unreliable equipment ensures that there is only one train on each 'block' of railway track at the same time. That forces trains to be at least 1 or 2 blocks apart, which are frequently multiple miles long. End result: Trains are usually 10's of minutes apart, or at least 1 minute apart even in urban subway systems.

A more advanced system would aim to have trains as close together as cars are on a freeway. Trains would be able to hitch and unhitch whilst moving 100 mph, allowing different loads to be sent different directions and different sets of passengers to stop at different stations. Crashes would be avoided by having every train know about the train ahead and behind, and unable to make any move which would cause a collision (ie. it is not allowed to slam the brakes on if there is a train right behind you).

Such a system would be implemented primarily on the trains, and primarily in software. Software is expensive to develop then cheap to replicate, a property very important if you want to deploy it widely.

It would be backwards compatible with fixed block signalling by simply saying that within each existing fixed block there is either one legacy train, or an unlimited number of gen 2 trains who will all communicate with eachother (and any train who cannot communicate with every other train within the block is not allowed to enter the block).

Hardware/software failures are kept safe by simulating every possible type of failure (ie. braking, locomotion, power, derail, position uncertainty, comms), and every second generating a plan which will be executed by every train in case of each type of failure occurring. Any move any train wants to make where any of the above plans cannot be generated with a safe outcome isn't allowed.

This is the sort of simulation/game, like Dwarf Fortress (especially older versions) where I don't have the slightest idea what's going on, or how to make things happen, but am still having plenty of fun.

See also: https://signalmaps.co.uk/#gwml1:1627

Live signal maps in the UK