Modern Image Signalling, Position and Types

I think we need to know a bit more about the function of the sidings before we can start giving advice.
(i) What is the purposeof the three shortish sidings on the front left? ie Engine shed, (sorry, depot!), goods sheds or a private works or....?
(ii) Why do they have their access via a separate line from the 'main line'?
(iii)What is the purpose of the three sidings front right which are accessed only by a reverse fron the bay platform?
(iv) What is the purpose of the two sidings on the right side accessed directly from the main line?

Also, re the through platforms - most modern prototype stations would have the through platforms bi-directional for greater operating flexibility and that means more signals would be needed.

If you can put some more information on the diagram and repost it, that would help.

Also are we talking about a surburban station with many commuter trains and few fasts, or a small town station that would have both fasts and some commuter trains? These are all factors which would affect the choice of signals on the prototype.

Regards,
John Webb

OK - I'll work with it as it is, but if there is any chance of the diamond cross-over (where the line from the bottom bay platform crosses over the line to the engine shed) being replaced with two points......
The reasons for this are that
(i) for the last twenty years or so diamond crossings have been kept to a minimum on the prototype;
(ii) to get a DMU out or into the sidings, the bay platform has to be clear of stock, which means the platform cannot have a train left in it; if there were two points instead of the diamond, the approach to the engine shed could be used as a head-shunt (as it would be in the prototype) allowing the platform to hold a train indefinately.

Two other coments:
1. Regarding the top bay platform, how do you get a train into it from the 'anti-clockwise' main line? It really means that that bay cannot be used for arriving passenger trains as they would have to make a shunting move - which isn't allowed on the prototype. The only way I can see of overcoming this is to alter the two points at the end of the upper island platform to face the other way. Any chance at all of a photo showing the whole of the track from the ends of the platforms to the right-hand side of the road bridge? That would help quite a bit.
2. The line from the 'Future Yard' only feeds trains onto the lower through platform, so that will be have to be bidirectionally signalled as well.

I'll try and post something with signals on in the next week, hopefully at the coming weekend.

Regards,
John

Right - some suggestions for possible modifications.

The easy one (?) at the 'West' end of the layout:


The reason for suggesting the extra cross-over is to allow trains from the 'Future Yard' line to gain access to the bi-directional platform line; otherwise the lower through line will have to be bi-directionally signalled as well.

The more complex suggestion at the 'East' end:
Crossover 1 takes trains to and from the South Bay line, but as sited cannot use Crossover 2 to get onto the 'clockwise' (outer) mainline, for which reason you need cross-over 3.
But light engines on the outer main line need to make a number of shunts to get onto the Loco line.
Likewise DMUs can only get to the lower DMU sidings via the South Bay platform.
Diamonds are not a favoured track formation on the modern Prototype; they are expensive to maintain and the track-circuiting and signal interlocking is, I understand, more complex.
There is no way in which a train on the inner (anti-clockwise) mainline can proceed direct into the North Bay.


By removing Crossover 1 I think you could use the two points to replace the diamond crossing. This still gives direct access from the inner mainline to the South Bay, and also allows the loco line to be used as a head shunt to the lower DMU sidings, while still allowing access to/from the South Bay.
Locos and trains from the loco shed and the South Bay can use the cross-over further to the 'East' (not shown on the diagram, but is on your sketches and photos above) to get to the outer main line.
Replacing Crossover 3 by a facing crossover allows trains on the inner main line to get to the North Bay, also DMUS to/from the sidings as well as other platforms with the minimum of shunting. Also light locos on the outer main can cross onto the inner main and then reverse back up to the Loco line with only the one shunt movement.

I do stress that these are suggestions only; the layout as it is is pretty good (I like the non-straight platforms particularly!) but just lacks a little flexibility which I think would be unacceptable from the prototype operations side.

Let me know in due course what you decide to do and we can then look at possible signal positions.

Regards,
John

Thanks to Edwin for his pertinant comments on the 'West' crossover.

My solution:


Uses two curved points, as did the first version which I've crossed out. Gives the Yard line access to and from the central bi-directional road but leaves the lower through platform completely usable without any restriction. (My addition to your drawing is not as neat as your original - I have to admit free-hand sketching has never been a strong point with me!)

Regards,
John

I spent a bit of time last night with copies of the Peco templates (the dotted white lines are the continuation of the track centrelines):

1. Your original layout at the 'East' end on the main lines, done mainly to get the spacing of the main lines and the location of the point to the DMU siding - this is just visible at the righthand end of the picture:



2. A possible facing points arrangement:



Uses two of the double curved points and two of the large radius points. This would seem to be pretty close to what you need with a minimum of disturbance to the remaining points - may need just a little minor adjustment to get things exactly right.

Regards,
John

Right, first post on modern signals:


The top part of the diagram show three-aspect signalling. The signals are spaced apart a bit over the braking distance of the fastest trains on the line so that if a train approaches a signal at the 'Caution' aspect (Yellow, by the way, in railway terms, not amber!) it has sufficient room to stop by the time it gets to the next, possibly Red 'Stop' aspect.

The lower diagram shows 4-aspect signals. They are spaced apart from each other at the braking distance of the slower trains (ie locals) using the line. They then continue to use the single yellow aspect as their 'Caution' warning. The faster trains then use the 'Double Yellow' as their 'Caution' warning and start braking sooner and are thus able to stop.

Both the above are for lines uninterrupted by points and stations, and the function of signals at these places I'll cover next.

Regards,
John

Junctions and stations - two important functions here:
1) stop trains colliding with each other by preventing 'conflicting movements'.
For example, where two lines merge, only one train can be allowed to proceed at a time and the trains must be stopped a little before the junction to give a safety margin.
2) confirm to the driver which route he is to take when he comes to a 'facing point' where he can take one of two routes - or maybe more if there are further points beyond the first one.

The signals used are of two types:



The 'feather' indicator is OK anywhere - but can only signal a maximum of 7 routes (straight ahead and three each side). The 'theatre' indicator is capable of showing more routes, but is restricted to stations where trains always approach at slow speed, so is used mostly at termini or major stations where all trains stop.

In the model world however we have an even smaller choice. No 'off the shelf' theatre indicators at all and three and four aspect signals with only position 1 or position 4 'feather' indicators! So unless you want to try and build your own there's not much choice! I'll look at this when we start planting signals on the layout.

Both the feather and theatre indicators will not show the route if the signal shows the Red 'Stop' aspect. If the route to be taken leads into a dead-end - the bay platforms in particular on your layout, the signal will only clear to the Yellow 'Caution' aspect. (Don't forget there will be a fixed red signal just in front of the buffers.)

Next instalment a bit later today, I hope.

Regards,
John

Shunting signals. In semaphore signalling days there were a number of forms of signal relating to shunting movements. These included small arm signals indicating the train was running into a siding or goods loop, there were various 'ground discs' and such things as 'calling-on' arms and 'shunt ahead' signals. All is simplified with colour lights:



The ground signal with two reds is the more recent LED (light emitting diode) version of the 'Ground Position Light' (GPL) signal, the older one having a common white bulb to both the 'Stop' and 'Clear' aspects. (With LEDs it's a great deal easier to make two colours in the one position.)

The Ancillary signal is the 'Clear' aspect of the GPL signal mounted under the main signal. It will only show the clear aspect if the main aspect is showing Red.

GPLs and Ancillary signals are used where a siding is to be entered, or a train is to enter a platform in which there is already a train standing. The meaning of the 'Clear' aspect is 'proceed with caution and be prepared to stop before the next fixed signal'. Where a GPL allows a train to proceed on any one of two or more routes, a stencil indicator or a small theatre indicator will show which route the train is taking. I'll try and dig a photo up of one of these sometime.

The rectangular black plate below the signal will have it's identity number on, telling drivers which signal they are at. This may be very important information for the driver to relay by phone or radio to the signalling centre if there are problems of any sort. The arrow shows to which line the GPL applies - they are small units and can safely sit in the 'six foot' gap between pairs of tracks and without the arrow there could be confusion.

In the modelling world there is at least one 'off the shelf' GPL signal available, and it can be worked either with the red/white or the red/red danger aspect. There is no model ancillary light available as far as I am aware, and this may mean a compromise by using a GLP instead.

Regards,
John

Here's a redrawn plan of your layout incorporating the revisions and with possible signal positions marked.
It is the custom to label signals for trains moving in one direction with the Odd numbers and those for trains moving in the opposite direction with Even numbers - this helps the signaller know in which direction the train is moving if the driver phones or radios in.



You may want to download and enlarge - I thought it would come out bigger!

And this is an explanatory list:



It's only in locating the signals I've realised the North Bay platform causes a problem - any chance of extending it to come off closer to the other points?

The big problem is Signal S12 which would need three 'feather' indicators when I know we cannot get them off the shelf!

Potential sources of model signals are the Berko/Eckon range - have a look at www.gaugemaster.com who are their main distributors; they are the same items, just one lot's ready-made, the other is in simple kit form. There's also Traintronics, a relative new-comer to the scene, but I can't find their URL.

Regards,
John