Perhaps 'the public' would do better if people like you actually bothered to explain issues rather than just get irrationally angry when people ask questions and ask for explanations?
I’m not angry; it’s just that in this instance the explanation of what’s actually happened would necessarily have to be so convoluted that it really is better just to announce “a signalling system failure”. But I’ll try anyway...
[BING BONG]
Ladies and Gentlemen..
In the signalbox at Doncaster, the signallers use a large physical control board called a ‘panel’ to control the signals and points. Earlier this morning a button on the panel which is used to set routes between signals in the Retford area broke. Because of the way the signalling interlocking works this then prevented any other routes in the area from being set and all the signals in the Redford area were stuck at red, so all the trains had to stop. This is because the safety of the entire railway system is predicated on the idea that trains stop at red signals and normally the default state for a signal is to show its most restrictive aspect, although this isn’t by any means always the case for various reasons. An ‘aspect’ by the way is what the railway calls the colour of light a signal shows, a bit like traffic lights on roads.
Luckily in case something like this happens there’s a system in place to ‘override’ the usual electronic link between the signalbox and the remote interlocking at Retford. This system would cause the signals to operate automatically without needing to communicate with the signalbox in Doncaster but it also means not all routes between signals would be useable, for a variety of complicated reasons. This is called the Override system. This morning the signaller attempted to switch in the Override as per his operating procedures but this didn’t work. It turns out this was because of a sticky relay in the interlocking. The failure of the Override to work meant that all the signals stayed at red.
In case something like this happens, there’s also a “remote panel” in the relay room at Retford. This is quite similar the signaller’s panel in Doncaster but it only controls the signals in the Retford area and is only used in an emergency when - for whatever reason - the electronic link between the signalbox and the relay room isn’t working or it’s necessary to switch it off. The relay room, by the way, is the building which houses all the relays and wires which make up the remote interlocking. There’s also an interlocking in the signalbox at Doncaster which deals with the interface between the various remote interlockings and the signaller’s panel and that’s what went wrong this morning when the button broke but don’t worry too much about that now. Anyway, because it’s physically located in Retford the panel has to be operated locally by staff who have to drive to site. Today once those staff arrived at the relay room it so happened that the remote panel also couldn’t be switched in when they tried because of the same sticky relay which was stopping the Override being switched in, although no one knew that at the time. This meant that the signals were
still stuck on red. Technicians who specialise in this sort of thing were called to see if they could find out why the Override and remote panel weren’t working. Once the technicians traced the fault and fixed the sticky relay, the staff who were on site to operate the remote panel were able to switch it in successfully.
However, by the time all this happened the railway had already implemented a degraded mode of operation called “Emergency Special Working” which allows train drivers to pass red signals under very carefully managed conditions to ensure they can move safety without the risk of colliding with each other. Because this method of operation had already been set up and trains were passing through the area, albeit at reduced speed, trains again had to be stopped and Emergency Special Working cancelled in order to safely being the remote panel into operation, again to eliminate the risk of having two trains collide.
And that, ladies and gentlemen, is why your train is late.