We'll start with the negative stuff: The live signalling diagrams are an experimental service provided at my own expense, primarily for my own entertainment. As such, it may be withdrawn at any time, temporarily or permanently.
With the above warning in mind, you are welcome to use the diagrams and pass on the details to others.
Network Rail make freely available a large amount of data, including timetables, train movements and many other areas. For much more information about this, see the Open Rail Data Wiki, where you can find out what is available, how to get it, and what I and others are doing with it.
The information on the diagrams is derived mainly from the train describers data feed from Network Rail. Currently I'm using describer areas M0, M1, and WA, which are MRROC Lime Street WestCAD, MRROC Liverpool Area WestCAD and Warrington PSB respectively. (MRROC is Manchester Regional Rail Operations Centre, located at Ashburys) The detail available varies from describer to describer, on some you can only see the signalling berths, while others also show signals and some of the route selections. Some of the berths belong to other boxes (See the FAQ below) and are provided in the data stream so the signaller knows what is coming. For these, we generally don't have signals.
The route selections are shown on the diagram either by highlighting the selected route through the junction or by means of a berth showing the name of the route. Note that these are not point indications - They indicate that the signaller has selected a route across the junction.
The black information panel displays details of each train shown on the diagram, if I can find it in my database. By the way, the time is from the working timetable so it may differ from public timetables, and might sometimes have an H for half appended.
The signalling data provided by Network Rail comes in two parts: Berth movements are easy to understand, "2F68 from 3592 to 3590" is pretty simple once you realise that berth 3592 is on the approach side of signal LL3592. On the other hand, the signal data provided is somewhat "unfriendly" in that they provide the information but no advice on what it means. It is left as an exercise for the user to decode the data stream. For a more detailed exposition of the process required to decode the signal data, see my notes on the Open Rail Data Wiki.
Only an on or off indication is supplied for each signal, with off corresponding to any of one yellow, two yellows, green, one flashing yellow, two flashing yellows, or two white dots. That is why the signals on my diagram only show green or red (or black when the information is missing.).
Working hard in the background is a small virtual server located in Nuremberg, Germany collects data from Network Rail, analyses it and stores it in a database. The database is then used to provide various web pages including timetable details, live departure boards and so on, including the live signalling page. Just one small part of the whole system is responsible for the real time signalling data which is used to drive the diagrams.
Each diagram is an SVG (Scalable Vector Graphics) file. This format was selected because javascript running on the client can easily update the diagram. The negative side of this choice is that older browsers don't support SVG.
Once the page has loaded, some javascript checks with the server for any updates on a regular basis and then alters the displayed diagram accordingly. I'd never designed anything like this before, and was pleasantly surprised how easy it was.
After playing with a couple of SVG editing tools which were annoyingly unsatisfactory, I ended up hand coding the SVG file, which was tedious but not too difficult. The M4 Macro Processor is used to automate common sequences such as signals and berths.
All the software involved is open source, and you can find it at https://github.com/philwieland/openrail. Feel free to download it and have a play, please let me know how you get on.
To learn more about the electrification in the northwest, see my Northwest Sparks web site and blog.
If anyone can supply a copy of the details of what the signalling bits denote, it would be very welcome. I've guessed almost all of them for the M1 describer, but one or two remain elusive.
I would also appreciate comments on the design of my diagram. What is the 'correct' way of indicating selected routes? How should I draw two berths 'in the same place' e.g. Huyton platform 2?
Currently, your browser contacts the server once every 4 seconds or so, to check for updates. I might take a look at streaming this information instead (More of a trickle than a stream, actually!). This would result in more timely updates, at the cost of a lot of programming effort for me.
Adding more maps will happen slowly, if at all.
You can contact me at editor at nw-sparks.co.uk