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> Ground Signals - Please help me to understand their placement, Swapping running lines
Art Dent
post 3 Mar 2018, 12:01
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Dear all,

Second query regarding operation and placement of ground signals. Here it is to allow locomotives to swap running lines. Era is mid 1960's, location BR Midland Region.

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 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.



I think (and I may be wrong in my assumption so please correct me) that I need a ground signal at position "U" (or possibly "T" for the lower line and at "R" (or "S") for the upper line - in each case the signal faces the driver of the locomotive?

Any help/advice/comments gratefully received.

Thanks in advance,

Art


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Bear 1923
post 3 Mar 2018, 13:14
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Exactly the same principles apply for this question as for your other (MPD) question.

1. On approach to any points train crew would see the face of a protecting Stop Signal. These would normally be in position P or W. Position Q or V would be "Wrong Side". possible - but a whole load of "technical" information.

2. The shunt (Non-Running) signals would be the same options as for the MPD. R S T or U being possible positions - all facing the opposite way to the Running (Stop) signals.

3. There's stuff I could add but this is the simplest solution.

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Bear 1923
post 3 Mar 2018, 13:35
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QUOTE (Art Dent @ 3 Mar 2018, 12:01) *
Dear all,


(A) to understand the requirement for, placement of and operation of ground signals.

(cool.gif but also (if simple) some explanation as to why.

Art


(A)

The "requirement" (without quoting the MoT Requirements) for all Fixed Signals is that enough are provided to do the regular job while not being so many as to cause confusion. Further Running Signals and Non-Running Signals must be distinct and not possible to confuse.

A Running Signal ALWAYS signals onto another Running Signal or buffer stop light. When cleared it authorises movement up to the permitted speed of the line as far as the next Running/Stop Signal. Trains being also restricted to the maximum permitted speed of what is in them.

A Non-Running Signal can signal onto another Non-Running Signal. a Running Signal or buffer stop light. When cleared it authorises movement at a speed which will allow the movement to stop dead short of any obstruction.

On Running Lines all movements approaching possible obstructions in the normal Running direction are controlled by Running Signals that protect the obstruction. Obstructions in this sense are basically points and crossings, level crossings and swing bridges.

All the other "little" movements are controlled by Non-Running Signals.


(B.)
Why signals are used.

(a) To avoid having to stop trains to give instructions to the crew. Also to avoid someone having to go out on the track to give the instructions.

This is not as "blindingly obvious" as it might seem. The early railways had to learn this - along with the need for interlocking.

(cool.gif Signals cost money. Initial capital cost, someone to work them and maintenance/renewal. Therefore only the signals that will be regularly needed get provided - begging the question of what will be regularly needed.

As previously mentioned - when a signal is not provided for a route that is needed verbal instruction and hand signals are used.

The logic behind where exactly any signal is placed is decided with regard to what the signal is and the need for train crews and others (such as shunters and platform staff) to see the signal. For Running Signals this may well be a need for sighting while approaching at speed.

I hope this answers your questions nice and simply.

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PS A Fixed Signal in this context is a signal on a post fixed to a structure or planted firmly on the ground. This means that it doesn't (usually) wander about so that train crews know where to expect to see it. This is distinct from hand signals which can wander about and appear anywhere.

There is an alternate definition of a Fixed Signal - as in a "Fixed Distant" - these are signals that can only show on aspect/indication.

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Bear 1923
post 3 Mar 2018, 13:51
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QUOTE (Art Dent @ 3 Mar 2018, 12:01) *


Art


I have dealt with shunt movements to/from the MPD and either way across the crossover.

There is a potentially relevant addition. A movement might be wanted to run Wrong Direction and not over the crossover - e.g. from RS toward P.

In LMR practice this would require two dummies (or two 2ft arms in position R) one above the other. Or an equivalent position light arrangement (more choices). In this case the top dummy/arm would signal the lefthand route over the crossover and the bottom arm would signal right hand route straight back route toward P.

In both cases the signalled move must run toward some limiting signal.

Across the crossover the route would run to a Stop Signal or buffer stop light. Straight back would run to another Non-Running Signal or to a Limit of Shunt.

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Art Dent
post 3 Mar 2018, 15:56
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Great Bear - I understood that.

I thought that the correct position for signals was P & R, U and W but I didn't appreciate that U and R would face "the wrong way" - i.e. orientated so that the driver running 'backwards' could see them. That makes perfect sense.

I thought that positions P, R, U and W would be used because drivers (except for the GWR) were on the left-hand side of the cab facing the direction of travel. I am also aware that in certain circumstances the fireman would be looking for signals on the right-hand side of the locomotive - hence the additional positions Q, S, T and V.

Thanks for taking the time to reply and clear some clouds of confusion that I had, it is much appreciated smile.gif

Kind regards,

Art


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Bear 1923
post 3 Mar 2018, 16:02
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https://farm5.staticflickr.com/4711/3878012...d8f974faf_z.jpg

Operation across from one Running Line to another Running Line.

Taking the upper line as the Up Line and the lower as the Down Line...ar of

i. A movement toward W on the Down Line that had not otherwise been instructed would be allowed to move toward W prepared to stop dead In Rear of the Stop Signal. If/when the signalman recognised the footplate crew (assuming he had a view of them) he might know that they were well versed in the local moves. If so he would clear the signal slowly as they trundled up to it.

ii. The crew would then ease forward until clear of the toe of the Trailing Point in the Down Line and In Advance (for this move) of the shunt signal T where they will stop. (In the 6ft Way this will be a ground signal - either a dummy or a position light).

iii. The footplate crew would then turn around to face the other way - obvious but this is relevant because all our thinking now turns around. This way round the loco and crew are In Rear of both the shunt signal and the toe of the crossover points.

iv. If the toe of the points is not clearly visible from the Box (so the signalman doesn't have a good clear view of it) the footplate crew will whistle the appropriate code to tell him they are clear.

v. The signalman will then reverse the points which will now be Facing Points for the next movement.

vi. The signalman will then clear the shunt signal T for the movement across the crossover.

vii. The loco crew will make the movement to the Up Line to a position In Advance of the Trailing Points in the Up Line and the shunt signals R.

viii. Again they will whistle code clear of the points if necessary.

viii. The signalman will return the shunt signal T to "On" and return the crossover points to Normal.

ix. For this case we will now turn our crew round to face toward the direction of Stop Signal P so that they can see the face of shunt signals R. They are now In Rear of shunt signals R (They will see the back of Stop Signal P).

x. For the loco to move back In Rear of Stop Signal P the signalman will clear the lower of the two shunt arms. (Being in the cess and not in the 6ft Way these signals {R} could be made up of two 2ft {shunt} arms one above the other}. The lower arm indicates the rout to the right.

xi. The loco may now move toward P through the points which are Facing for this movement.

xii. This loco movement will continue, ready to stop short of any obstruction or the next shunt signal or Limit of Shunt board.

xiii Once the loco is fully clear of the points and In Rear of Stop Signal P (where the crew will be able to see its face) the signalman will put shunt signal R back to "On".

------

The best way to get this into your head is to make a diagram of the track on a big sheet of paper and use a block of wood as the loco. If you really want to have fun you can also make simple signal.
Doing this in 3D is not silly. It's the proven best way of getting trainee signalmen to learn workings.

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Bear 1923
post 3 Mar 2018, 16:40
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QUOTE (Art Dent @ 3 Mar 2018, 15:56) *
Great Bear - I understood that.

I thought that the correct position for signals was P & R, U and W but I didn't appreciate that U and R would face "the wrong way" - i.e. orientated so that the driver running 'backwards' could see them. That makes perfect sense.


A movement line to line over the crossover would not stop anywhere between VW and TU. It would run clear of TU to where the crew would be able to see the face of the signal. When the points are reversed the interlocking in the Box releases the shunt signal. When pulled the wire for the shunt signal runs through a mechanical detector which proves the point blades in the correct position for the shunt across the crossover. If the blades do not prove the shunt signal cannot clear. This results in mechanically detected points usually having their shunt signal close to them - so there is limited distance between the signal and the toe of the points in most cases. This means that there is no room for anything to stand between the signal and the points - so no "go backwards" indication
    So signals have their backs to where the movement they signal is going.
    If the signal were the other way round it would face the same way as the Running/Stop Signal - which would create a confusing message to train crew.


QUOTE (Art Dent @ 3 Mar 2018, 15:56) *
I thought that positions P, R, U and W would be used because drivers (except for the GWR) were on the left-hand side of the cab facing the direction of travel. I am also aware that in certain circumstances the fireman would be looking for signals on the right-hand side of the locomotive - hence the additional positions Q, S, T and V.


No. The Bot/MoT Requirements from 1889 onward always Require that signals are normally put on the immediate left side of the line to which they apply or no further to the right than above the centre line in normal practice. Anything right of the centre line is "Wrong Side". Wrong side does happen for various reasons - it gets complicated. In practice this left of the line applies to Running Signals. Non-Running Signals, particularly taller shunt signals can often be seen on the right of the line to which they apply - unless they would cause other confusion.

Put it this way... On Running Lines Running Signals will normally be on the left in the cess. Shunt signals tend to be on the left - when faced - this puts them in the Six Foot Way. However shunt signals can also be in the cess - with their backs toward the backs of the Running/Stop Signals.

In all cases the equal priorities are not to cause confusion and to be readily sighted by train crew as appropriate.

Another consideration is that you have assumed that the driver would be on the left hand side of the cab (except the GWR) when facing the direction of travel (running right direction on the left hand line)... And chimney first... However... What about running tender or bunker first? ohmy.gif cool.gif

Positions Q and V for Stop/Running Signals would require a Ten Foot Way for a signal post or for the signal to be bracketed out over the line. Either of these Wrong Side signal positions would normally only be caused by the signal being approached on a left hand curve - or some structure obscuring sighting of the normal signal position.

Positions T and S are the conventional positions for shunt ground signals - in the Six Foot Way - where they are each on the left of the track to which they apply for their controlled direction of movement. In these cases R and U are the Wrong Side positions in the cess.

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Art Dent
post 3 Mar 2018, 17:51
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Ahh..

I thought I was getting a handle on this and then ...



Are you saying that there would be ground signals at all of the following locations:

Upper (Up) running line at "R" facing against the normal direction of travel and at "S" (again facing against the normal direction of travel) and similarly for the lower (Down) running line at "U" and "T" (both facing against the normal direction of travel)?

To check my understanding, and considering a loco initially moving from right to left (chimney first) on the lower (Down) line and swapping onto the upper (Up) line to run left to right (tender first) ...

There would be a normal semaphore signal (red arm, white band or colour-light signal) at "W" (and a similar one at "P"). When cleared, the loco (running light) would proceed to beyond T/U and stop. (I'm guessing that the semaphore would be changed back to 'Stop' once the loco had passed it. This to prevent other trains proceeding?).

Driver whistles to tell signalman he is stopped beyond T/U and is awaiting a movement instruction.

Signalman sets both points (which would be intelocked together and also interlocked to the signals) to allow the loco to move from Down line to Up line.

Signal at "P" is set to 'Stop' and ground signal at "U" is cleared.

Loco moves slowly from Down line to Up and may continue along Up line (running backwards/tender first) until it encounters another signal or stop just beyond "R" if it was to then run right to left (chimney first) along the Up line for shunting purposes (where it would have to wait for the points to be changed and ground signal "R" (or "S") to be cleared.

Once clear of the points on the Up line, loco driver signals to signalman (by whistle) that he is clear.

"P" still held at 'Stop', points now moved to the normal running line direction on both the Up and Down lines and the signal "U" is also changed to 'Stop'.

Signals "S" and "T" would be used for a loco moving tender first from the Up line to the Down line.

There wouldn't normally be any signals at positions "Q" or "V" unless on a fast main line with a 10-foot or on a left-hand curve where the normal signals to the left of the running line may not be seen??

Have I got that correct as per this diagram?



Seems to me like I have misunderstood something here as "T" & "U" and "R" & "S" duplicate each other and you said that signals are expensive to install & maintain. Surely there would be only one signal at either "U" or "T" and similarly one at "R" or "S".

"T" and "S" would be used for locos running in the wrong direction (ie chimney first for the Down line running left to right??)

Cheers,

Art


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Bear 1923
post 3 Mar 2018, 19:43
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One the 1st issue - each pair of dummies are alternate positions - one signal would be used. For the Stop signals the cess position (left of the track is the standard position. The wrong side position (alternate) would be in a 10ft Way or up on a bracket or gantry.

That's all for tonight.

Perhaps for tomorrow you ould do a diagram fro your track arrangement for the loco getting from the MPD to the Up Line? - With signal positions you figure and point numbers.

Talking of which - you should have a Trap Point on the loco exit. Also both ends of any pair (crossover or exit and trap) would have the same number - the end closer to the leverframe is the A end while the further end is the B end.

I'm off for some sleep now.

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PS - basically you are heading in the correct direction. biggrin.gif
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Art Dent
post 3 Mar 2018, 22:10
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Hi Bear,

This is kind of what I had in mind ...



Distance "X" to "Y" is much longer than indicated here - diagram has been compressed. Easily fit a decent couple of trains between them end-to-end.

The crossing allows locos from trains to enter/leave MPD and to run around at the station area.

I've mirrored the crossing and signals at the right-hand end of the station - signals "M" and "R" as well as ground signals "N" and "P".

"R" protects the station entrance and crossing (Home Signal?), "W" is acting as a Starter Signal and protection for the crossing. Similarly with "P" and "M".

Ground signals "P", "U", "R" and "N" are for run-around purposes.

"B" controls movement into MPD and/or along the Down Main.

"F" controls movement onto the Down Main.

Trap point (not shown) would be to the left of "B" (to catch errant locos from the MPD??)

This is probably nothing like this would be signalled i reality - as long as it is a "reasonable approximation", I'm happy.

Not going for block working and overlaps and such just a flavour.

Am I sort of in the ball-park with this?

Kind regards

Art


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John Webb
post 3 Mar 2018, 22:46
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Trap point would be on the exit from the MPD just after the ground signal F and before point 'X', so if a loco passes F when it shouldn't, it won't reach the main line. The trap point and point 'X' would be operated together as if they were a cross-over like 'Y' or 'Z' in your diagram.
You are getting quite close now!

John Webb

PS I've listed a number of books, as have a few others, in a thread pinned to the start of this signalling sub-forum. You might find Bob Essary's book "Railway Signalling and Track Plans" (Ian Allan, ISBN 978-0-7110-3215-6, published 2007) of assistance in particular in understanding the railway signalling system.
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Bear 1923
post 4 Mar 2018, 06:56
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Hi John! biggrin.gif

Personally I don't specially rate Bob Essery's book. But then, I was a signalman and he was a driver - so different perspectives...

I've also added some websites in the pinned thread.

If you can locate them on E Bay there are also some good small books for railwaymen by JNO Aitken - c1950s. The Ian Allen basic signalling books are also basic.

Essential book to read - Red for Danger - LTC Rolt.

Getting into technical/practical stuff - Lewis Mechanical Railway Signalling (c 1925). However, the reproductions (print on demand) are poor quality for the price - and original copies do show up quite often at the same or lower prices.

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Bear 1923
post 4 Mar 2018, 08:22
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QUOTE (Art Dent @ 3 Mar 2018, 17:51) *
Once clear of the points on the Up line, loco driver signals to signalman (by whistle) that he is clear.


Yes - unless the position can be clearly seen by the signalman... The "neighbours" tend to get a tad upset by "too much" whistling... However, the railway is usually there by Act of Parliament while residences are usually only there by Common Law... Guess what the railwayperson's view tends to be...

QUOTE
"P" still held at 'Stop', points now moved to the normal running line direction on both the Up and Down lines and the signal "U" is also changed to 'Stop'.

P, protecting the points in the Up Line, would be at Danger/Stop/On/Red the whole time the crossover is in use. The interlocking in the lever frame would prevent the crossover being worked if the Stop Signal (Running Signal) P were not at Stop - or - to be precise - if the lever were not correctly back in the frame. This could be backed up by detecting the signal arm - in that case an electrical lock on the crossover (points/black) lever would lock up the crossover points lever.
As soon as the points lever begins to be worked from normal (back in the frame) the signal (red) lever for P is locked by the interlocking.

Also - as you noticed - back at the start of the shunt across - when the loco has moved passed W to beyond T/U W would be put back to On/Stop. If W is not On/Stop then the points cannot be moved - again they are held by the interlocking in the same way that P would be interlocked.
Just when W gets put back is a little open to discussion. Strictly it should not be restored in the frame until the loco is at least clear of the trailing points in the Down Line of the crossover. This holds the points (by the interlocking) and prevents the signalman beginning to swing the points to Reverse until the loco is clear of the toe of the points. While a too early movement of the blades would probably be pushed through by the loco there would be some risk of a derailment and both the point blade ends and the point rodding would be damaged. The signalman could end up looking for a new job.

QUOTE
Signals "S" and "T" would be used for a loco moving tender first from the Up line to the Down line.


You've got this a bit wonky.
(i) forget about which way round a loco is. It's not relevant. Only which way the crew are looking and which way the loco is going to move are significant.
(ii) while opposite directions across a crossover do sometimes get signalled by the one lever (both signals working to the one pull) it is very unusual - because opposing moves are extremely rarely signalled - usually only where there will only ever be one loco present - as in "One Engine In Steam" working.
(iii) Occasionally, where an existing frame is deficient in spare levers for an amendment, one lever will be used for opposing indications - with the On/Stop position being mid-segment (of the frame arc plate) - one shunt signal is then cleared by pulling the lever and the other is cleared by pushing the lever. This is not common.

QUOTE
There wouldn't normally be any signals at positions "Q" or "V" unless on a fast main line with a 10-foot or on a left-hand curve where the normal signals to the left of the running line may not be seen??

That is basically correct. Q and V would be instead of P and W - except for a very few rare exceptions - where a co-acting arm (or aspect) was provided horizontally for sighting. Co-acting arms and aspects are usually provided vertically.

QUOTE
Have I got that correct as per this diagram?



Almost - subject to the notes mentioned.

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Bear 1923
post 4 Mar 2018, 09:28
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blink.gif OOPS! wacko.gif You had already provided the diagram this morning...


QUOTE (Art Dent @ 3 Mar 2018, 22:10) *
Hi Bear,

This is kind of what I had in mind ...


Forget the "main line" - this only applies where there is a branch line - and it is included in the term "Up Main" or "Down Main". At the other end (away from the branch) the lines would simply be marked as "Up Line" or "Down Line". "Main tends to be an expression popular with enthusiasts and modellers - learnt from the hobby literature.
Also, please become familiar with the terms "Running Line" and "Non-Running Line". A Running Line is - at minimum - a through line on which journeys are made - so - frequently mis-called a "Main Line". A Non-Running Line is - at minimum - all the rest - sidings, refuges, depots etc - where movements are made slowly.
Non-Running Lines are normally segregated from Running Lines by Trap Points or similar arrangements.

QUOTE
Distance "X" to "Y" is much longer than indicated here - diagram has been compressed. Easily fit a decent couple of trains between them end-to-end.

Oh no you do not!!!! At least - not like this.
Compression for the diagram is no problem - Box diagrams are schematic not to scale.
That said (ignoring that you haven't said whether the trains you want to fit in are passenger or goods - and how long... unsure.gif
While Signalboxes in this kind of layout might be mid way between crossovers the mechanical boxes were limited in how far the lever could be from the further points of a crossover (or any other points). This essentially limited most run rounds on one Box to 500 yards. (Yes, this also limited train length). When a longer arrangement was needed there had to be a Signalbox at each end. This gets into all sorts of wild and exotic stuff. dribble.gif
Add to that - in normal working od Block Systems of signalling the system only allows one train in one section at one time. This applies to the Block Sections - between boxes for Absolute Block Working and derivatives. It also applies in the area of control of any one Signalbox/Block Box - which is called "Station Limits". Between any two consecutive Running/Stop Signals only one "item" (train or vehicle) is allowed at one time - except - because attachments and detachments need to be made (and sometimes two passenger trains need to be at a platform at the same time) movements can be authorised into already occupied sections of track by either subsidiary signals or shunt signals - these indicating movements at low speed prepared to stop short of any obstruction.

QUOTE
The crossing allows locos from trains to enter/leave MPD and to run around at the station area.

Best to forget this statement. smile.gif

QUOTE
I've mirrored the crossing and signals at the right-hand end of the station - signals "M" and "R" as well as ground signals "N" and "P".


Oh no you haven't!!!!!!! tongue.gif

Crossover "Z" is a Facing Crossover. Naughty! mad.gif
In most cases "Z" should probably be a Trailing Crossover - like "Y". Simply copy the arrangement at Y to X. You do not need to include D at Z - W does the job.
There would be a signal C on the Down Line approximately in the area of the word "Down" - this limits the shunt out from the MPD and stops it trundling off over the horizon.
Similarly there needs to be a Stop Signal out to the right beyond M and the (corrected) Trailing Crossover - to stop escape in that direction.
The signals at Z will be the same as at Y.


QUOTE
"R" protects the station entrance and crossing (Home Signal?), "W" is acting as a Starter Signal and protection for the crossing. Similarly with "P" and "M".


R is some kind of Home Signal - whether a Home, an Outer Home or an Inner Home depends on where the Box is.
Don't confuse a passenger/goods station (platforms and sidings) with "Station Limits". The Block System is about signals and track - it doesn't care about platforms - and sidings are broadly ancillary - the structures of concern being the points and crossings in the Running Lines - which the Block System is there to protect and control.
Signalboxes/Block Posts are supposed to be placed where the signalman has the best, continual view of the track under his control when standing at the lever frame.

W is a Starter if the Box is between R and W. This looks to be unlikely to me. The Box is more likely to be between W and D - although - I hope that length is fairly short? If it is short shunt signal U may not be needed.
If the Box is between W and D R is an Outer Home and W is an Inner Home. D then becomes a Starter and the C you need (if only in theory) becomes an Advanced Starter.
P is a Home Signal - probably an Inner home Signal - with another Stop Signal to the left of it by 440nyards - making P an Inner Home. M is then a Starter with an Advanced Starter beyond it to the right.

QUOTE
Ground signals "P", "U", "R" and "N" are for run-around purposes.

The ground signals are there to control shunt movements of any kind. Where the LMS/LMR wanted more than one route to be available to be signalled they would have used a disc (or 2ft arm) for each route. So U and R and the corrected signals at the other end would be two disc. If U can go B would be a three disc.
Come to that - if U can go we can potentially lose D.

QUOTE
"B" controls movement into MPD and/or along the Down Main.

As above - B needs to be two discs - or three if there is no U.

QUOTE
"F" controls movement onto the Down Main.

F controls movement onto the Down LINE.

QUOTE
Trap point (not shown) would be to the left of "B" (to catch errant locos from the MPD??)


THINK ABOUT THIS!!!!!

QUOTE
This is probably nothing like this would be signalled i reality - as long as it is a "reasonable approximation", I'm happy.


Subject to corrections and/or amendments this is very much like a real railway layout. The only significant differences in track layout are the possible extended lengths between R and W and W and D. Otherwise the only difference is that you have an MPD instead of a goods yard.

QUOTE
Not going for block working and overlaps and such just a flavour.


Forget about overlaps - you simply don't have space for them. Also, for your period overlaps were something that visibly applied to Track Circuit Block (TCB) signalling and not mechanical/Absolute Block signalling.
There is no way you will make signals look right without the context of Block Signalling of one kind or another! This does not mean that you have to Block Work.

QUOTE
Am I sort of in the ball-park with this?


Kind of...

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post 4 Mar 2018, 09:32
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QUOTE (John Webb @ 3 Mar 2018, 22:46) *
Trap point would be on the exit from the MPD just after the ground signal F and before point 'X', so if a loco passes F when it shouldn't, it won't reach the main line. The trap point and point 'X' would be operated together as if they were a cross-over like 'Y' or 'Z' in your diagram.
You are getting quite close now!

John Webb

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