Rail3D*

 

Semaphore Signals

 

Some notes on the correct use of (uk) Semaphore Signals.

If you have not already done so, please download the latest “Steam and Semaphores” Package which contains updated signal definitions.

Richard Southey has also made some Lower Quadrant Signals for Rail3D. The difference between lq and uq is the way they move when cleared, the first moving to a lower position and the other moving to an upper position. The types are not usually mixed in general working.

Unlike modern colour light signalling, Semaphore Signals are usually controlled from a local signal box, and are thus arranged in groups around a signal box, with relatively long gaps in between.

The simplest arrangement is a single Stop signal (known as a Home signal) and a Distant Signal to give approaching drivers advance warning:

 

The distance between the two needs to be enough for the fastest trains to safely stop from full speed. The picture only shows a short distance between the two: in practice on a fast mainline the distant signal might be a mile or more.

 

Usually the above simplest arrangement is insufficient and signal boxes will usually have more (stop) signals, these additional signals may be:

  • A starter: a signal ahead of the home signal, which controls trains starting towards the next block post.
  • An additional home signal, positioned before the home signal and called an ‘Outer Home’
  • An additional starter, beyond the first starter and referred to as an ‘Advanced Starter’
 
Probably the most common arrangment is Distant >> Home >> Starter

Note that in all cases there will only be one distant signal and it will be positioned sufficiently before the Home or Outer Home that the fastest trains can be brought to a stop between the distant signal and the first Stop signal.

 
 

Implementing in Rail3D

This is very straightforward to implement in Rail3D. The below assumes the use of uq (Upper Quadrant) signals

 
  1. Lay the track.
  2. Place the Home and Starter signals.
  3. Place a Distant signal sufficiently far before the Home signal. It is easy to use either the “Distance between markers” function, or “Show Distance from Zero” functions to measure a sufficient distance.
  4. In Rail3D semaphore signals are always controlled signals.
  5. Set the Distant signal to type “uqd”(Upper Quadrant Distant). Ensure that the following flags are set or checked:
    1. controlled should be set
    2. distant should be set
    3. stop should be cleared
    4. semaphore should be set
  6. Set the Home signal to type “uqh” (Upper Quadrant Home). Ensure that the following flags are set or checked:
    1. controlled should be set
    2. distant should be cleared
    3. stop should be set
    4. semaphore should be set
    5. section should be cleared
  7. Set the Starter signal to type “uqh” (Upper Quadrant Home). Ensure that the following flags are set or checked:
    1. controlled should be set
    2. distant should be cleared
    3. stop should be set
    4. semaphore should be set
    5. section should be set

The important thing in order to get the distant to operate correctly (And trains to run properly) is the use of the section flag. There should only be one section signal: and it is the last signal - the signal that controls trains running into the next section. In Rail3D, a distant signal only clears if the all the signals up to, and including, the next section signal are clear. The distant signal will not monitor signals beyond the next section signal.

So the correct order of signals is:

  1. A distant signal.
  2. Zero, one or more non-section signals
  3. One section signal

and repeat at the next block post.

A useful option in Rail3D is to select “Show Signal Type Flags” from the “Signals” menu.

 

This displays the flags set for each signal. With this, you can run a train around your layout and quickly check that the correct flags are set on each signal.

 

 

MRG 03/12/2014 11:34:28