Now is the bit I find most exciting, the Signalling Design.
Now that I have a track plan is fixed in terms of number tracks, turnouts etc. (for model signalling, it isn’t critical whether the track plan changes in dimensions slightly), I can think about the signalling, luckily I can use Fareham’s Signalling Plan to base the design on, but I must alter this to fit my track layout and my operating requirements.
The operation requirements in the real world are subtly different to those in the model world. In real life operational requirements are all about the requirements of the operating department to ensure that the railway can be reliably run the train service required by the train operating companies and there are the facilities that allow the signallers to run trains in times of perturbed working.
In the model world, the operating requirements are more based around what the owner would like to be able to do, which may not be the same as those moves you would to in real life. However, they do tend to match up.
The basic operational requirements can be broken down into the following:
Through Trains – What type of services, both passenger and freight, are to run through the layout, this can dictate the the number of aspects and even the method of working on certain lines
Trains Turning Back – Whether trains need to turn back either in a platform or on plain line
Trains Requiring Running Round – Mainly relating to Freight Trains, but can relate to Passenger Trains, this sort of requirement should say, what trains require running round, how they will do it and where they will do it.
Attaching / Detaching Trains – Also known as ‘Permissive Working’, do trains, mostly passenger, require to be attached and detached in platforms?
Platform Sharing – Do trains (who aren’t attaching / detaching) need to share a long platform?
Depot / Yard Working – How does the operator want the Depot / Yard to be controlled; by the signaller, by a shunter, by some other means. How are trains going to arrive and depart the yard.
For Collingwood, my operating requirements as follows:
- Stopping Passenger services from Portsmouth to Southampton / Portsmouth to Eastleigh / Southampton to Portsmouth / Eastleigh to Portsmouth
- Non-Stop Freight services from Portsmouth to Southampton / Portsmouth to Eastleigh / Southampton to Portsmouth / Eastleigh to Portsmouth
- Non-Stop ECS / Departmental services from Portsmouth to Southampton / Portsmouth to Eastleigh / Southampton to Portsmouth / Eastleigh to Portsmouth
Trains Turning Back:
- Passenger / ECS / Departmental services turning back in Bay Platform
- ECS / Departmental services transferring between Platforms
Trains Requiring Running Round:
- Non (Track layout doesn’t allow it)
Attaching / Detaching Trains:
- Trains Turning back may attach and detach in Bay Platform (two 2 car units)
- None (Platforms not long enough)
Depot / Yard Working:
- Aggregate Terminal to be worked by Ground Frame released from signal box and controlled by shunter
- Aggregate Trains arriving from Eastleigh / Southampton into Platform 3: Train loco to propel into Reception Line, loco to detach and pull into Platform 3 & run to Eastleigh, Shunting Loco to shunt train as needed.
- Aggregate Trains arriving from Portsmouth (Short Train): Runs into Reception Line, Train Loco Detaches and waits, Shunting Loco to attach to rear and shunt train, Train Loco to be released at some point to run to Eastleigh.
- Aggregate Trains Departing for Eastleigh: Shunting Loco to form train and pull out into Platform 3, Train loco to attach and shunting loco to detach, Train to depart, Shunting Loco to run back to Yard
- Aggregate Trains Departing for Portsmouth: Shunting Loco to form train in Reception Line, Shunting Loco shunts back to headshunt, Train Loco to back onto Train and depart from Reception Line.
So with those, plus what I’ve taken from the real Fareham Signalling Plan, this is my signalling plan:
So, why did I design what I did? Well, I’ll run through each signal from left to right and why it is there.
CD285 – Limit of Shunt – This is provided at Platform 1 at Fareham to allow non-passenger trains to shunt from other platforms into Platform 1.
CD813 – 2 Aspect Dorman Signal – Again, this is provided at Fareham (E813), but I’ve reduced it from a 3 Aspect to 2 Aspect Signal and made it controlled with an Automatic Working Facility rather than a fully Automatic Signal. This is because it is much easier to get an aspect sequence, as there is nothing to activate the yellow aspect easily.
CD814 – 2 Aspect Filament Head with Position Light – This is to allow Aggregate Trains departing towards Eastleigh to depart straight away on the single line and allow access into the Aggregate sidings. As the Aggregate Siding will non-track circuited, I have to use a Position Light into the yard.
CD810 – 3 Aspect Dorman LED Searchlight Signal with Position 1 Junction Indicator – Just like Fareham this is the Up Platform 1 Starter, the Junction Indicator is for the route round towards Netley. Both routes from these signals are delayed replacement and the route around to Netley has an automatic working facility so I can run things without a signaller from time to time.
CD812 – 3 Aspect Filament Head with Standard Route Indicator – Again a real Fareham Signal, as this signal is controlling trains from a terminal platform and has more than one route (one towards Eastleigh and one towards Southampton), then it must be provided with a route indicator rather than a junction indicator
CD825 – 3 Aspect Filament Head with Position Light – This time, not a real signal at Fareham, but based on one at Southall (simply because it was on a scheme plan I was working on at the time I was thinking about). This signal is different to the others as the Main Aspect is controlled by the signaller, whilst the Position Light is controlled by the Aggregate Terminal Ground Frame (more on that later). The reason for this is actually in the control side of things. I want to use computer control / JMRI to control the signals, but use a relay interlocking and ground switch panel to control the area of the ground frame, as these can’t interact easily (or at least not with my competence!), then separate signals have to be used, so I decided to provide the main aspect and position light which means I can separate out the systems.
CD283 – ‘Red-Red’ Ground Mounted Independent Position Light – This is signal is actually provided in the middle of the junction at Fareham. This covers moving trains between platforms, although seen as I took out one of the Crossovers, then it only covers moves between Platforms 1 & 2. The reason for it being in the middle of the junction is that it means it can control turnback moves on both the Netley and Portsmouth Lines without having 2 signals. I have also provided stop car markers to provide ‘rear-clear’ markers.
CD811 / CD821 – 3 Aspect Dorman LED Searchlight Head with Position Light and both Miniature & Standard Route Indicator – These signals protect the entry into the platforms. As both signals have more than one main class route, they must be provided with some form of route indicator. As one route is into a Bay Platform they must be provided with a Standard Route Indicator, a Junction Indicator can’t be used to indicate into a terminal platform. Both signals are also provided with permissive routes into the platforms to permit attaching of units, these moves being authorised under a Position Light. Again, there is more than one permissive route, and under current standards, then a Miniature Route Indication has to be provided.
CD808 / CD822 – 2 Aspect Filament Head Signal Both signals are real, but are provided here to protect the fiddle yard. In reality, these are 2 aspect signals, but even if they weren’t I would of made them 2 aspect for the same reasoning as CD813
You may have noticed I left out the SPAD Indicators from the above. I thought I would go over these seperately.
SPAD Indicators are ‘ronseal signal’, they do exact what they say on the tin, they provide a driver with an indication that a signal has been passed at danger. If a driver sees one illuminated, even if he has not himself caused a SPAD, must stop immediately. The signals themselves are a standard 3 aspect head with a blue backboard. They are normal unlit, but when they are activated, they show a central red aspect with the word ‘STOP’ across the middle sandwiched between a pair of flashing red aspects.
SPAD Indicators are rare and no longer used or installed, they were provided at signals which were deemed to be at high risk of being passed at danger and were such an incident would cause significant consequences.
So, why provide them on Collingwood, particularly when they don’t exist at Fareham? Well, you might have realised, I like weird and unusual signals, plus I have a fairly plausible reason why they might be provided in reality at Fareham:
The reason is that it could be quite easy to SPAD CD811 and run onto the junction whilst a train is crossing in front of it. This because the Netley lines on the approach to Fareham are in a cutting, very bendy and fairly high speed (50mph), plus some trains don’t stop between Southampton and Fareham. This could all contribute to a line speed SPAD which could carry a train onto the junction.
Equally SPADing of CD810 / CD812 is fairly highly as the area is DOO, meaning there is a higher risk of a train starting against a signal at danger, and as these signals are so close to the junction, this could mean a train could be carried onto the junction. Hence why I’ve said the SPAD Indicators are active if something SPADs CD810, CD811 or CD812 even though they are plated as indicators only for CD811.
As mentioned further up and in the previous entry, I have decided that the aggregate terminal will be controlled by a Ground Frame.
The reason behind providing a Ground Frame is to allow the Aggregate Terminal to be shunted without involvement of the signaller. My Ground Frame controls the 3 independent position lights control movements within the Aggregates Terminal as well as the points between the Reception Line and Down Siding.
The Ground Frame is released by the signaller when 590 points are normal, this prevents the ground frame from being used when trains are entering / exiting the terminal. The Ground Frame also has an acceptance lever which prevents CD814’s position light from being pulled off until the shunter is ready.
All the shunt signals controlled by the Ground Frame are last wheel replacement as they will be passed by propelling moves.
The last thing to mention is the safety systems that I will model, namely the Automatic Warning Systems (AWS) and Train Protection & Warning System (TPWS) installed on today’s railways.
The Automatic Warning System was made mandatory after the horrific crash at Harrow & Wealdstone in 1956 that killed 112 and injured 340. This a system that provides an audible and visual indication to the driver of the state of the signal ahead as they approach. I won’t go into the exact detail of how the system works, so if you want to know more, I recommend this webpage
The on-track equipment associated with it are called AWS Inductors, NOT RAMPS as they are commonly called by modellers, and consist of at least a permanent magnet in a housing, most AWS Inductors also contain an Electromagnet that is energized by the signalling showing a Green Aspect. Some AWS Magnets (for those advanced speed warning boards or signals that are incapable of displaying a Green Aspect), a permernant magnet is the only thing that is provided, and both types can be suppressed where trains travel over it in the other direction, to prevent non-relevant activation of the trains systems.
AWS Magnets are fitted to on the approach to Main Aspect Signals, Stopboards, Fixed Distant Boards, Advanced Speed Warning Boards and some Level Crossing Signage. The Exception to the rule is where a Main Aspect Signal has no Main Class routes reading up to it. Shunt Signals are not fitted with AWS Magnets.
For Collingwood, I would have to provide extra strength Southern Region Green Magnets, due to the magnet fields of the Electric Motors, the AWS Magnets have to extra strength to be received by the detector on the train (a simplistic explanation, but it’ll do for now).
I have provided AWS Magnets for all my Main Aspect Signals, bar CD812 and CD814 as they have no routes reading up to them. I have suppressed the magnets for CD822 in the Down Direction as trains pass over it in the Up Direction and the opposite for CD813s AWS Magnet.
TPWS was introduced in 2001 as an alternative to the introduction of Automatic Train Protection. Again, I won’t go into it’s operation, so have a look here and at this video on Youtube:
The on-track equipment consists of two systems, the Train Stop System (TSS) and Overspeed System (OSS). the TSS is placed at the foot of the signal (-20/+2m), whilst an OSS is fitted at varying distances on approach to the signal, but no closer than 25 meters. Both systems consist of two cables attached to two separate grid like frame, these are known as loops and NOT GRIDs, and emit two different electrical frequencies (an Arming Frequency and a Trigger Frequency). For the TSS, the two loops are fitted immediately adjacent to each other, whilst OSS Loops are fitted with a variable separation distance between the two loops.
There are three commonly believed myths about TPWS:
- TPWS prevents SPADs
- TPWS is designed to stop all trains within the Overlap
- TPWS is fitted to all signals.
Myth number 1 is simply not true, there is no train protection system other than total Automatic Train Operation that prevents a SPAD (even ATP and ETCS can technically have signals passed at danger). TPWS merely reduces or removes the consequences of a SPAD.
Myth number 2 is generally wrong, normally TPWS is not designed to stop a train within the overlap, instead it is designed to stop a train before the conflict point ahead of the SPAD signal. It just so happens that with a TSS, a 40mph train fitted with enhanced braking will probably be stopped within the Overlap and with an OSS, this speed is increased to 75mph. There are cases where the TPWS is designed specifically to stop a train within the overlap, but these are deviations from the standard scope of TPWS design.
Myth number 3 is also generally wrong, TPWS is generally only fitted to signals capable of displaying a red aspect (including Stop Boards) and protecting a junction conflict. So, Automatic Plain Line Signals, Distant Signals and Independent Position Light Signals used for shunting are not fitted. The exceptions to the rule are signals designed using the Modular concept (all main aspect signals capable of displaying a red aspect are TPWS fitted) and Signals limiting bi-directional moves, so limit of shunt signals and fixed reds.
On Collingwood, all of my signals barring CD808 and CD813 are both capable of displaying a red aspect and are protecting a junction conflict, so they a TSS, as the speeds are low around Fareham and the conflict points tend to be fairly far away, none of the signals are fitted with OSS’. Note that CD825 should have a TSS fitted, but I have managed to miss it off the scheme plan!