Notes On The Rules Of Signalling


Some notes on the prototype signalling rules and practice

Clearing and restoring signals

  • Normal practice is to clear signals in the order trains approach them, eg Outer Home (if present), Home, Starter, Advanced Starter (if present).
  • A distant signal cannot be cleared unless all the home and starting signals following are cleared (unless local instructions dictate otherwise).
  • Signals should be returned to danger when the whole train has passed the signal
    • If a train comes to a stand (Eg at a station stop) when the engine has passed the signal, but before the whole train has passed the signal, the signal may be returned to danger.
    • Where a signal protects (and is interlocked with) points, the signal is not returned to danger until the whole train has cleared the points. For example, at Charnton Rd no 2 signal would not be returned to danger until the train had cleared nos 23 and 29 points.

Welwyn control and related issues

There were a number of significant railway crashes, including (off the top of my head) Welwyn and Ais Gill, where signalman “forgot” trains were there and effectivly ended up sending two trains into a section at the same time.

This is easily done, especially at a busy box like Charnton Rd (it’s most easily done when taking over a box, and not realising there is a train standing at number 4 starter).

What happens is that you forget there is a train standing at the starter, and when a following train is offered, you clear all the signals for it to run through. The train that was standing at the starter now moves off - but is starting from cold - and the other train - which is running at speed - runs into the back off it.

Various solutions were used in the prototype to deal with this:

  • Linking signals to track circuits so you couldn’t clear a signal is there was a train already in front.
  • “Signalman’s reminder appliance” - various forms of metal or wood collar that fits over the lever handle and stops you from moving the lever. The idea was that when you had to hold a train at a signal (esp one out of sight), you put the collar over the lever of the previous signal to remind you, then when you later tried to move that lever you’d say to yourself “What’s that doing there .. oh yes there’s a train standing in front. Oops!” Mind you, I have known the thought process go “What idiot left that there”, takes off collar, moves lever anyway ….
  • The rule book requires the train crew to remind you they are there if detained for any period - usually achieved by the fireman coming to the box (And required to sign the register to prove he has done so).
  • Welwyn control (or sequential locking). This is a form of interlocking that forces the signalman to operate the levers in the correct sequence. So, if the home signal is pulled and then released, the sequential locking would prevent it being pulled again until the starter has been pulled and released. So, if you’ve got one train past your home signal, you can’t let another one past until the first has moved on from your starter.

None of these are currently possible in Rail3D - but they are all ideas for the future.


See also

« Notes For Real Signalmen | Signals | Semaphore Signals »

MRG 14/02/2014 12:10:48