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> Ground Signals - Please help me to understand their placement, MPD Entrance/Exit and signalling
Art Dent
post 3 Mar 2018, 11:55
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Dear all,

Have sought numerous places for information on ground signalling and either haven't got the information sought or understood what I was told so I'm looking for some help in order to understand the requirement for, placement of and operation of ground signals.

I basically have two locations that I'm looking at which I will post in two different threads to avoid confusion in any replies.

Firstly, entrance from a main line into a motive power depot (see picture below) - era mid 1960's, location BR Midland Region.

I need someone to confirm my understanding. Please don't get too techinical, it is just the placement of the signals initially that I'm bothered about, but also (if simple) some explanation as to why.



Basically (and please correct me if I'm wrong), I think that the entrance to the MPD from the main line would have a ground signal either at position "B" or "D" - facing the driver of the locomotive. Possibly "A" or "C" (under what circumstances?)

Also for locomotives leaving the MPD they would have a ground signal "F" (or possibly "E" ?)

I'm guessing that the signal would be the disc type rather than the 3-light type (again some advice as to the most appropriate signal would be appreciated, together with colour of signal - eg red band on white circle or red and two white lights, etc). In each case the signal faces the driver of the locomotive?

Thanks in advance,

Art


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Bear 1923
post 3 Mar 2018, 12:58
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1. Last question first - if a signal doesn't face a driver he can't see it - so it can't apply to him - so train crew always look at the red/yellow/green side of a signal for instruction.

2. Signals only apply to stopping (or cautioning) and authorising movements from the approach side of the signal to pass them. They do not instruct "go past me and come back". Id a movement from beyond the signal needs to come back or set back into another line (or across a crossover) then an additional signal or two will be required - those signals will face the opposite way from the first signal - because the movement will have gone beyond them and the crew will have to turn round to look back for the fresh direction they will travel in.

3. Not all possible routes are signalled. Signals cost money. Therefore only commonly used routes are provided with signals. Where a signal is not provided a movement may be authorised by a verbal instruction and hand signal.

4. Your "main Line" - I take to be a Running Line. This will have a Running Signal - i.e. a 4ft Stop Arm or a Multiple Aspect (2 to 4 aspects depending on what Running Signal comes next) Stop Signal. This would normally be in position D. This signal protects the Fouling Point - movements through the points. For your period this might only be a 4ft Stop arm or MA Stop. However, on the LMR, either might have a subsidiary Draw Ahead signal - (2ft) arm or position light.

5. Going past the points the signal to set back into the MPD would be either a disc signal (aka "dummy") or a position light. Both would be likely to be ground signals. Each could be in position either A or B. If in position B and circumstances caused it the dummy or position light could be on a short post.

6. (a) To emerge from the MPD you could have either a Running Signal (4ft arm etc) or a Non-Running Signal (dummy etc). Question being - do locos leaving want to run at line speed (= Running Signal) or dawdle up to the next signal ( = Non Running Signal).
6. (cool.gif The position can be F or E - but F is a bit more likely. Also F as a dummy/position light can be raised on a short post (for better sighting).

7. In LMR practice both B and F could be 2ft semaphore arms on posts instead of a dummy or position light.

8. You can do some mixing or matching of dummies, 2ft arms or position lights. However, any shunt signal between parallel lines would be on the ground.

I hope this listing is clear/simple enough. cool.gif
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Art Dent
post 3 Mar 2018, 15:46
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Thanks very much, Bear.

A very clear and informative reply - just what I was hoping for.

I just need a further couple of things from your reply clarfiying (being a signalling noob).

1). A 4ft stop arm is a semaphore signal on a short post??

2). Disc signals like this (shown below) are referred to as 'dummy signals'??



3). What is a 'Position Light/Position Signal'? Is it one of these (pic below)



Regarding your point 6) my intention would be for a loco to emerge from the MPD at walking pace to then reverse along the running line (against direction of travel if allowed) to its train or to swap onto an adjacent running line to move (in reverse) in the right direction only to swap lines again to join its train. Not too clear how this operated in reality so any help/info here would be much appreciated.

I'm also puzzled by "yellow bar" ground signals (on either a white disc or black disc) such as this (pic below).



Are these some kind of distant signal for shunting operations?

Many thanks for your time and patience in dealing with such 'noob' questions.

Cheers

Art


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Bear 1923
post 3 Mar 2018, 17:23
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QUOTE (Art Dent @ 3 Mar 2018, 15:46) *
Thanks very much, Bear.

A very clear and informative reply - just what I was hoping for.

I just need a further couple of things from your reply clarfiying (being a signalling noob).

1). A 4ft stop arm is a semaphore signal on a short post??


No. A four foot arm - the length is of the arm itself - not including the spectacle plate (Except with a GW SB arm). The 4 ft arm is the standard signal arm for Running Signals for Stop and Distant arms. The height is "as appropriate". The latest replacement/modified signalling Stop arms tend to have the red/yellow aspect at Driver's Eye Level the same as Colour Light Signal signals. Driver's Eye Level is 12ft above rail head.

QUOTE (Art Dent @ 3 Mar 2018, 15:46) *
Thanks very much, Bear.

A very clear and informative reply - just what I was hoping for.

I just need a further couple of things from your reply clarfiying (being a signalling noob).

1). A 4ft stop arm is a semaphore signal on a short post??


No. A four foot arm - the length is of the arm itself - not including the spectacle plate (Except with a GW SB arm). The 4 ft arm is the standard signal arm for Running Signals for Stop and Distant arms. The height is "as appropriate". The latest replacement/modified signalling Stop arms tend to have the red/yellow aspect at Driver's Eye Level the same as Colour Light Signal signals. Driver's Eye Level is 12ft above rail head.

QUOTE
2). Disc signals like this (shown below) are referred to as 'dummy signals'??


These can be called "dummies". They come in one, two or three stack configurations - very occasionally a four stack. Sometimes two by two or whatever combination. The top disc always applies to the left most route while the bottom disc applies to the right most group. With a two by two the left stack counts above the right stack.

QUOTE
3). What is a 'Position Light/Position Signal'? Is it one of these (pic below)


That is one variety of position light signal - basically a shunt signal in that case. In this case the arrow indicates that the movement controlled is to the right - however, this is not the standard LMR use of these arrows. Where is this signal?

QUOTE
Regarding your point 6) my intention would be for a loco to emerge from the MPD at walking pace to then reverse along the running line (against direction of travel if allowed) to its train or to swap onto an adjacent running line to move (in reverse) in the right direction only to swap lines again to join its train. Not too clear how this operated in reality so any help/info here would be much appreciated.

Okay... Before anyone else tells you - locos and trains do not "reverse" - they "set back". That said I will try to get to this issue tomorrow.

QUOTE
I'm also puzzled by "yellow bar" ground signals (on either a white disc or black disc) such as this (pic below).



Are these some kind of distant signal for shunting operations?


No this is a "Yellow Dummy" - more tomorrow...

QUOTE
Many thanks for your time and patience in dealing with such 'noob' questions.

Cheers

Art

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Bear 1923
post 4 Mar 2018, 07:38
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QUOTE (Art Dent @ 3 Mar 2018, 15:46) *
3). What is a 'Position Light/Position Signal'? Is it one of these (pic below)



This is an old style position light - incandescent electric lamps behind the aspect colours and lenses - as distinct from the modern LED ones. These older ones showed Stop as in the picture with a red and white. The white was called the "pivot light". Proceed was shown by extinguishing the red and lighting the white above it - this gave a diagonal pair of white lights - somewhat replicating the "Off" of an Upper Quadrant semaphore arm.
You can see that the lens of the white aspect that isn't illuminated looks blue - this was to colour correct the light given off by the incandescent lamp.
BE ADVISED!!! Railway signals DO NOT use "bulbs". Bulbs are what you plant in the ground! mad.gif
Behind the signal can be seen the detection rods from the point blades going to an electric detection box. (This is the grey box just beyond the orange "don't tamp me" cable protection tube. (Unfortunately a lot of tampers seem to be colour blind sad.gif ).


QUOTE
I'm also puzzled by "yellow bar" ground signals (on either a white disc or black disc) such as this (pic below).



Are these some kind of distant signal for shunting operations?


Okay, I noted above that this is a Yellow Dummy/Yellow Shunt Signal/Yellow Disc. I want to get you to figure a few things out so I'm going to ask you a few questions...
    Q1. What does a Distant Signal do?
    Q2. Where is a Distant Signal found? (Part of your answer might pick up on some terminology I've recently used here or in your other post).
    Q3. What do dummies do?


Also look at the Yellow Dummy and the pair of Red Dummies - apart from the disc faces these are made up of the same LMS/LMR components. "Standardisation!"

QUOTE
Regarding your point 6) my intention would be for a loco to emerge from the MPD at walking pace to then reverse along the running line (against direction of travel if allowed) to its train or to swap onto an adjacent running line to move (in reverse) in the right direction only to swap lines again to join its train. Not too clear how this operated in reality so any help/info here would be much appreciated.


Again - getting you to think it through... Wrong Direction shunt movements have to occur - e.g. for things like run-rounds of goods trains at through stations. So - Wrong Direction shunts do get authorised. Where they have to happen regularly they are provided for by Fixed Signals - as mentioned before.
Fixed Signals always authorise to a fixed location - be it another Fixed Signal, a buffer stop lamp or a Limit of Shunt (for shunt signal moves).
Where a Fixed Signal is not provided verbal instruction and hand signal can be used - BUT! - these have to be VERY clear about the limit of travel of the movement. Such movements are usually instructed to be "at caution".

Providing a diagram of the lines you want to work over (including the Trap Point -even if you haven't modelled one ohmy.gif ) would show me something of what you are understanding so far and also give me signal and point numbers to reference. smile.gif
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