Collingwood IECC - Creating a Prototypical IECC for a Model Railway

[jamespetts]

Excellent - thank you for the link.

[St. Simon]

Part 17: Axle Counters

 

Since I’ve made a change to the layout to include a pair of axle counter sections over the harbour bridge, I’ve now got to make changes to the signalling screen and interlocking.

 

History

 

Before I go into the principle of operation and how I’ve modelled them on the layout, I’ll go into the history of Axle Counters.

 

The first use of an Axle Counter for train detection was at Glasgow Queen Street in 1967 due to problems of insulating a steel bridge from the required track circuits. After this, Axle Counters were generally only installed where providing a Track Circuit was troublesome or impractical, although they were particularly favoured in Scotland. Axle Counters first becoming widespread in 1999 when Queen Street was converted to all Axle Counters, and since then they have become the go to train detection for most resignalling.

 

The public probably became aware of Axle Counters in 1991 when it was suspected (although never proved amongst several theories) that an unauthorised reset of an Axle Counter section within Seven Tunnel on the 7th December caused the signal protecting the section to clear with a train within it, meaning a Sprinter could enter the occupied section and subsequently collide with the rear end of an HST.

 

Currently, there are three types of Axle Counter used in the UK from two manufactures. There is the traditional bolted ‘H’ series AzLM type from Thales which is most common; the clamped ‘K’ series AzLM type from Thales and the clamped RS123 from Frauscher, which is quickly becoming the favoured type despite being very new to the UK market.

 

Axle Counters vs Track Circuits

 

This question has been argued and debated many times.

 

The advantages of an Axle Counter over a Track Circuit is that they are unaffected by any sort of conditions that would cause a Track Circuit to fail, such as rain, heat, snow, flooding (up to a point obviously, but much more tolerant than a Track Circuit), rusty rails and poor ballast resistance. Also, there are no joints to maintain, meaning less maintenance. With clamped Axle Counters, such as the ‘K’ series AzLM or RS123 is that they can be easily modified by simply loosening the head and sliding it along the rail (and extending / shortening the cable) rather than having to cut in a new joint. Axle Counters allow any vehicle with a flange to be detected, whereas there are lots of rail vehicles that can’t be relied upon to operate Track Circuits. Then there is the simple fact that they are more reliable than Track Circuits, which was the reason that over Christmas 2021 all the Train Detection sections between Paddington and West Drayton was converted to Axle Counters.

 

Having just said that Axle Counters are much more reliable, the disadvantage is that this requires careful setting up and installation, otherwise they can give trouble. Axle Counters must also be carefully positioned to prevent a train stopping with a wheel directly over the head, as a train slightly rolling back and forth when stopping or starting can confuse the evaluator. Axle counters also require data links and more complex interlocking and control date (see next section). If you have ever done PTS course for the railway or done P-Way Training for Axle Counter areas, you are told to never wave anything metal near it as it confuses it, this is only partially true. In fact, it is only a shovel that could affect the operation of an Axle Counter, whereas Ballast Forks, Pickaxes etc. won’t (but still, DON’T wave anything metal near an axle counter!) Another disadvantage is the fact that an Axle Counter won’t detect anything leaving the rail (such as through a derailment or an RRV coming off at an access point), but this can be managed through other means.

 

The most common ‘disadvantage’ of Axle Counters that is put forward is that of Broken Rail Detection. It is true that an Axle Counter will not detect a broken rail, however it is NOT TRUE that a Track Circuit WILL detect a broken rail, in practice it takes a clean split in the rail by quite a few mm in dry conditions for a broken rail to cause a Track Circuit to fail. Track Circuits have never been relied upon to detect broken rails and were never designed to do so. For instance, the broken rail that caused the Hatfield Rail Disaster was not detected by the Track Circuit over it. However, if you still believe that this is an overwhelming problem, then the standards to say that the maintenance regime must ensure that broken rails are picked up through other means (although this should be the case already) if Axle Counters are to be installed.

 

The current standards on the provision of Axle Counters is that they are the mandated standard Train Detection to be used for resignalling projects, IF it is intended for E.T.C.S. to be commissioned within 10 years of the resignalling (as Axle Counters are the preferred Train Detection for E.T.C.S.), however, they are pretty much standard Train Detection for most re-signalling.

 

My personal view is that Axle Counters are generally superior and more robust compared to Track Circuits, but Track Circuits do still have their place on the Railway

 

Operation

 

Axle Counters, be they Thales AzlM or Frauscher, all work on the same principle. The system consists of three core components, the Head (the image being a 'H' series Thales AzLM head):

 

 

The Electrical Junction Box, also known as the 'Yellow Mushroom' (the image being a newer Thales EAK30K type, although the traditional Thales EAK30H is seen behind):

 

 

And the Evaluator (which I don’t have a photo of but is a computer module within a lineside location or within the interlocking room, but you won’t see that as a member of the public).

 

The head consists of a pair of transmitters (Tx’s) on the inside of one of the running rails, and a pair of receivers (Rx’s) on the outside of the running rails. The use of a pair of Tx’s and Rx’s allows direction of a train to be determined. The transmitter emits an electrical field around the rail head as below (the red and blue lines):

 

When the flange of a rail wheel passes over the head, it disturbs the electrical field, as below, causing a change in the resistance detected in the Receiver:

 

 

This change in resistance is passed to the electrical junction box (which also generates the field), which analysis this change and passes the information onto the evaluator, as (in basic terms) a wheel count (including direction), miscount or fault. The evaluator uses the information to count the number of axles into a section and then count the number of axles out. If the resulting value is anything but ‘0’, then the evaluator tells the interlocking the section is occupied and if it is ‘0’, then the interlocking is told the section is clear.

 

From an interlocking point of view, if everything is going well and working normally, axle counters and track circuits work identically, sections become occupied and then clear as trains pass through them. It is when things go wrong that they are very different. With a track circuit, the signaller doesn’t have to do anything before normal signalling can resume once the fault is fixed. However, axle counter sections require the signaller to reset / restore the section before normal signalling can resume once the fault is fixed.

 

The Reset / Restore Procedure

 

There are four types of reset:

 

·         Co-operative with Aspect Restriction = This is where the signaller and a technician lineside need to both carry out actions to reset the section, this is banned in new installations, but can be found in older installations.

·         Conditional with Aspect Restriction = This is where the section will only reset if the last ‘count’ was out of the section (i.e., it is most likely the train has left).

·         Unconditional with Aspect Restriction = This is used when Engineering Possession & Special Train Reminders are used and will reset the section whatever its state is.

·         Preparatory = This is similar to conditional, but requires a train to actually prove the section is clear before the reset is successful and doesn’t apply aspect restriction

 

Almost all installation nowadays are Conditional / Unconditional. This is the reset that I’ve modelled on Collingwood.

 

 

Axle Counter sections are portrayed differently to Track Circuits on a VDU workstation. They are identified by a (X) suffix and have a red roundel next the section I.D. In reality this roundel would act as the ‘button’ and indication, but on Collingwood I’ve added the word ‘reset’ as the ‘button’ for the signaller to push.

 

The reset procedure is generally carried out within the evaluator rather than in the Interlocking or Control System. Most resets are carried out after an Axle Counter Section fails to clear once a train as fully left it, therefore it is a pre-requisite that the section shows occupied with no route locking or routes set over it before a reset can take place. A reset can’t be performed if the section is disturbed (i.e. there is a fault somewhere within the head, junction box or evaluator):

 

 

On Collingwood, my Axle Counter ‘failure’ is done manually by the signaller via a ‘Miscount’ button on the fault panel (just like the Point and Signal Lamp Failures shown in previous posts).

 

Before the section is reset, it is procedural that the signaller applies an Engineering Reminder on the protecting signal (this isn’t enforced by the interlocking, just by the rule book):

 

 

To reset the section (which restores the ‘count’ of the section to ‘0’ and effectively makes the section go clear), the signaller presses ‘reset’ (or the just red roundel in reality). This causes the red roundel to go to a solid red circle whilst the evaluate resets it’s count to ‘0’, which can take a few seconds (on Collingwood, this is simulated by adding in a timing delay before the reset shows as successful):

 

 

Once the evaluator has successfully been reset, the section clears. However, this causes a problem in that the signaller, nor the evaluator, knows for certain that the section is physically clear (the failure of the section to clear might be because the whole train hasn’t left the section). This could mean that the signal could be cleared with a train in the section (exactly what was suggested had happened in the Seven Tunnel collision). Therefore, to prevent the signal clearing when the section goes occupied after a reset, something called ‘Aspect Restriction’ is applied to the protecting signal.

 

Aspect Restriction is where the signal is held at red despite the route being clear until it can be proven that the reset section is physically clear. This is done by talking a train past the signal at red at caution (a speed from which the driver can stop within their sighting distance), and if the train successfully pops out the other end without the section failing again, it can be taken that the section is actually clear (if it isn’t the train driver will stop and phone the signaller).

 

Whilst Aspect Restriction is in place, a dark red ‘Indication of Restricted Route’ background is shown around the signal and section that is being reset, to tell the signaller why the signal is not clearing):

 

 

Once a train has passed through the section and the section re-clears, the Aspect Restriction is removed and the IRR is no longer displayed. The signaller can then set routes normally.

 

What you see above is the routine for plain line sections, however it gets very complicated for sections involving points, dependent on where the Axle Counter heads are positioned on the ‘heel’ route at a turnout.

 

If the head is placed within 10m of the clearance point of the turnout, then the Aspect Restriction can be removed by a single train running along either route of the turnout. This is because the driver will be able to visually inspect the other route from the one they are taking up to 10m past the clearance point, anything further than that, it is agreed that the driver won’t be able to see.

 

So, if the head is placed more than 10m from the clearance point, then Aspect Restriction is applied separately through both routes of the turnout so that two trains, one along each route, would be required to fully remove Aspect Restriction. This can be both an advantage and a disadvantage, as it does require complex data and can mean a specially route train if one route is rarely used, however, it does mean that you could use on route normally despite one part of the section still being in a failed’ state whereas a track circuit failure would mean neither could be used unless the whole section is cleared.

 

Simon

 

Edited May 2, 2022 by St. Simon

[5BarVT]

18 minutes ago, St. Simon said:

The first use of an Axle Counter for train detection was at Glasgow Queen Street in 1967 due to problems of insulating a steel bridge from the required track circuits. After this, Axle Counters were generally only installed where providing a Track Circuit was troublesome or impractical, although they were particularly favoured in Scotland. Axle Counters first becoming widespread in 1999 when Queen Street was converted to all Axle Counters, and since then they have become the go to train detection for most resignalling.

Hadn’t realised Queen St axle counters were the first but I knew they were early (AzL 65).  Other early ScR axle counters were Mid Calder Jn to Carstairs as part of Motherwell resignalling for West Coast electrification and Forth Bridge as part of Edinburgh resignalling, again, because the rails are mounted directly on the steel structure.

Queen St (1999) was the first (and only) AzL 90-4 in the U.K. (got trips to Amsterdam and Stuttgart out of them!).

Paul.

[Ncarter2]

As I understand, there is a fourth system

in use in the Uk, from Siemens. It covers the Bournemouth and Portsmouth areas. As a track engineer, I prefer Axle counters on the whole, but they can be a pain when it comes to maintenance of the track, particularly when using Rail Grinders, OTM’s etc. 

I have enjoyed reading your description, very insightful for a mear ballast basher.

[Bucoops]

Definitely very interesting. As a mere layperson I was aware of axle counters but (wrongly) assumed they worked on a broken beam principle. Interesting that two sensor pairs so close together with the field distortion method can react fast enough to be reliable.

[St. Simon]

On 24/04/2022 at 03:49, Ncarter2 said:

As I understand, there is a fourth system

in use in the Uk, from Siemens. It covers the Bournemouth and Portsmouth areas. As a track engineer, I prefer Axle counters on the whole, but they can be a pain when it comes to maintenance of the track, particularly when using Rail Grinders, OTM’s etc. 

I have enjoyed reading your description, very insightful for a mear ballast basher.

 

Hi,

 

Yes, I think you are right that the SIMIS-W interlockings at Bournemouth & Portsmouth might use Seimens Axle Counters, but I think they were one-offs and any SIMIS-W systems in the UK (such as the Crossrail core) now use Frauscher systems. I've certainly never heard Seimens mentioned as a provider when discussing Axle Counters on any of the schemes I've been involved with.

 

Rail Grinders are the biggest Achilles heel of Axle Counters, it is an old joke that Axle Counter heads just give the Rail Grinding operator something to aim at in the same way that across track orange piping gives Tamper operators a target!

 

On 24/04/2022 at 12:25, Bucoops said:

Definitely very interesting. As a mere layperson I was aware of axle counters but (wrongly) assumed they worked on a broken beam principle. Interesting that two sensor pairs so close together with the field distortion method can react fast enough to be reliable.

 

Axle Counters do seem to be a sort of 'magic box of tricks' to a lot of modellers and rail industry people, but I assume is that we are so used to Treadles, infra-red or other non-magnetic counting systems in our lives that people get slightly confused when they find out Axle Counters don't use any of the 'obvious' methods of counting.

 

Fraucsher specify that the RS123 sensor works upto 450km/h (280mph), and I know that all the systems are used very reliably on High Speeds Lines all over the globe, but I do agree that it is amazing that they can react so quickly!

 

Simon

Edited May 2, 2022 by St. Simon

[St. Simon]

Hi,

 

After thinking for a while that I would love to write a book detailing what is in this thread, but also realising that it would be a very boring book for most people and would never be published, I've decided to look at writing up a booklet to be professionally printed and sold for a small fee from the layout at Exhibitions, starting with the Great Electric Train Show in October.

 

If this is something you would like to see, I would appreciate it so that I don't go down an expensive rabbit hole for nothing!

 

Regards,

 

Simon

[guspaul]

On 21/07/2022 at 21:39, St. Simon said:

Hi,

 

After thinking for a while that I would love to write a book detailing what is in this thread, but also realising that it would be a very boring book for most people and would never be published, I've decided to look at writing up a booklet to be professionally printed and sold for a small fee from the layout at Exhibitions, starting with the Great Electric Train Show in October.

 

If this is something you would like to see, I would appreciate it so that I don't go down an expensive rabbit hole for nothing!

 

Regards,

 

Simon

Yes definitely!

[imt]

On 21/07/2022 at 21:39, St. Simon said:

If this is something you would like to see, I would appreciate it so that I don't go down an expensive rabbit hole for nothing!

 Yes indeed.  All fascinating to me BUT a huge amout of work.  I have always wondered if RMWeb might be able to drum up a "dump thread" process which would allow me to keep the things I am interested in and edit out (what to me are) occasional irrelevancies.  It would provide a base text to start from perhaps?

[milan243]

On 21/07/2022 at 21:39, St. Simon said:

Hi,

 

After thinking for a while that I would love to write a book detailing what is in this thread, but also realising that it would be a very boring book for most people and would never be published, I've decided to look at writing up a booklet to be professionally printed and sold for a small fee from the layout at Exhibitions, starting with the Great Electric Train Show in October.

 

If this is something you would like to see, I would appreciate it so that I don't go down an expensive rabbit hole for nothing!

 

Regards,

 

Simon

 

The booklet is a great idea. I would buy one.

[BusDriverMan]

A quick and dirty method is to go through the thread page-by-page and "Print to PDF" each one. (Browser menu, Print, select "Print to PDF" from the list of printers, set page scale to 50%, hit Print, choose a filename and location to save.) It's very far from perfect but means you can still refer to it come the day your ISP shuts down due to rising power bills.

 

However if someone had done the hard work of filtering out the off-topic posts (like this one) and collating a booklet, that'd be worth a couple of quid to me too.

[St. Simon]

Hi,

 

I’ve been trying to get a move on with this, but as I’ve been concentrating on getting the layout finished for GETS, I won’t be able to finish the booklet to get it printed in time.

 

I’ve got the content (more than just than what is on this thread) 90% ready, it’s now getting it into a presentational state for printing and selling.

 

I’ll continue with it and will let people know when it is ready!

 

Simon

[St. Simon]

Hi,

 

For those that are following this thread, tomorrow evening at 19:30 I'll be giving a talk on Modern & Model Signalling Systems at the Model Railway Club, which will include some details on Collingwood including some exclusive videos on how the panel and interlocking operate! It is a hybrid in person / zoom talk and you can find more info here:

 

Modern & model signalling systems - The Model Railway Club

 

Simon

[St. Simon]

Hi,

 

I have been busy this week producing this for the layout:

 

 

Yes, you might be saying why do I need to produce a 'panel' for the layout when I already have one, but actually I've re-drawn the panel.

 

Why? Well, several reasons, firstly there were a few changes that I needed to make to the signalling to make improvements to the operation. This required changes to the screen layout. Secondly, there several poorly drawn areas in the old panel (there were lots of white lines around the double junction thanks to the fact that JMRI doesn't like diagonal edges on graphics), so I wanted to make a 'cleaner' panel, it may not seem like much has changed but it is noticeable. Thirdly, there well a few elements missing thanks to space, so I made everything a little smaller and more spaced out. Finally, there have been some changes in standards and controls that I wanted to incorporate.

 

The other thing was that I have had several people ask me for the graphics so they can produce their own workstations, however the original panel was all totally custom. With this new one, I have now developed a modular set of graphics that can be used to create any layout. I'm not sure whether I'll make these available to people or not yet.

 

So, what are the big changes?

 

• 'Cleaner' modular graphics for a more consistent look
• Collingwood Viaducts are now shown
• Junction Names now shown, with 596A/B gaining the name 'Funtley Junction' (Funtley is an area between Fareham and Botley).
• New Warner Route provided from CD816 to CD810 using a Restricted Phantom Overlap. This allows a train to come into Collingwood Station when a train is departing the, something that was frequently at the Basingstoke show
• 596A Trap Point now shown (as it is now required for the signalling)
• CD822 now has a 'swinging' overlap so that trains can approach it whilst something is routed out of the Eastleigh Fiddle Yard and vice versa, again something which was frequently needed at the Basingstoke.
• CD808, which protects the Southampton Fiddle Yard, has now become a 'Controlled Intermediate' Signal. This was part of the new standard which has seen Automatic Signals banned for new works.
• 'On Train At a Time' or OTAT controls are provided for 596A Points at Funtley Junction. Another newly introduced thing.

 

I'll do more posts discussing Controlled Intermediate Signals and OTAT Controls in the future.

 

Simon

Edited August 7, 2023 by St. Simon

[St. Simon]

Overlaps

 

Overlaps seem to be something which is often just stated when talking about signalling for model railways, often quoting the distance of 180m. The reality of overlaps is quite a lot more complicated and varied.

 

The concept of an Overlap is simple, it is a section of track beyond the exit signal of a route that is proved to be unoccupied to prevent a collision in the event of a minor overrun as the result of a SPAD.

 

Not all signals require any overlap, the basic rules being that an Overlap is not required when you don’t have a signalled route up to a signal, the signal is on a freight only line and doesn’t protect a passenger conflict, where a permissive move is being made or for Buffer Stops.

 

Currently, there are several types...

 

This is an extract of one of a series of posts about the signalling of Collingwood on my blog here, which includes several videos on how the interlocking works.

 

Simon

[St. Simon]

'One Train at a Time' (OTAT) Controls 

 

 

 

OTAT, or ‘One Train At a Time’ controls is something newly introduced into UK signalling principles and is a form of degraded working and are associated with Flank Protection.

Flank Protection is where facing points are used to divert run-away or SPAD trains away from a head on / side on collision with a legitimately routed train. There are two places I need Flank Protection on Collingwood. One is to protect trains signalled from CD811 across Collingwood Junction from trains passing CD810 or CD812, which requires 594 Points ‘Normal’:

 

 

The other place is at Funtley Junction, protecting a train signalled from CD821 from a SPAD of CD822, using 596 points ‘Normal’:

 

 

It is in the latter case where OTAT controls are required. OTAT was introduced in March 2022 and is part of ‘Level 2’ or ‘Enhanced’ Flank Protection.

 

This is an extract of one of a series of posts about the signalling of Collingwood on my blog here, you can see a video of OTAT working as well.

 

Simon

[The Stationmaster]

Simon if I read that Funtley Jcn as it appears in that screen shot example it implies that trap point on passenger lines are back in fashion.  Am I correct in that impression?

[St. Simon]

36 minutes ago, The Stationmaster said:

Simon if I read that Funtley Jcn as it appears in that screen shot example it implies that trap point on passenger lines are back in fashion.  Am I correct in that impression?

 

Hi Mike,

 

You are reading it correctly, but no trap points aren't back in fashion for passenger lines. 

 

In real life, that junction has a trap point (not sure why, but I assume it is something to do with the turnback shunt in the middle of the junction) as per the model. I had previously ignored the trap point in the signalling data has it wasn't needed, but I'm including it now to allow me to have a swinging non-called overlap at CD822 for operational ease!

 

I don't think in real life we'd include a trap point in these controls, I've used it purely as  way of explaining the principle of the controls.

 

Simon

[Nick C]

1 hour ago, St. Simon said:

In real life, that junction has a trap point (not sure why, but I assume it is something to do with the turnback shunt in the middle of the junction) as per the model.

I've only just noticed the turnback shunt - it might be a daft question, but what use is it, given that there's no route from it to the down Portsmouth line?

[St. Simon]

37 minutes ago, Nick C said:

I've only just noticed the turnback shunt - it might be a daft question, but what use is it, given that there's no route from it to the down Portsmouth line?

 

Hi Nick,

 

Again, not really sure!

 

In real life, I think it is probably used to shunt stuff between all three platforms, probably during times when Fareham is used as a blocking point for a possession (although I'm not sure if this is how Fareham is used). I.e., a train can come into Platform 1 from Portsmouth, terminate and then shunt into Platform 3 for going back to Portsmouth.

 

On Collingwood, as I've left out out the crossover that would allow you to go from the Up Portsmouth to the Down Portsmouth in the Down Direction (to save cost and space), if I think would only use it to shunt a failed train from Portsmouth into the Bay and then back into Platform 1. I haven't actually used it though!

 

Simon

[The Stationmaster]

23 hours ago, St. Simon said:

 

Hi Mike,

 

You are reading it correctly, but no trap points aren't back in fashion for passenger lines. 

 

In real life, that junction has a trap point (not sure why, but I assume it is something to do with the turnback shunt in the middle of the junction) as per the model. I had previously ignored the trap point in the signalling data has it wasn't needed, but I'm including it now to allow me to have a swinging non-called overlap at CD822 for operational ease!

 

I don't think in real life we'd include a trap point in these controls, I've used it purely as  way of explaining the principle of the controls.

 

Simon

Thanks Simon - that makes perfect sense having the trap there to create a swinging overlap.  (You might even find an E10,000 circuit for that in the office archives as there was one at Reading, and possibly elsewhere).

[5BarVT]

33 minutes ago, The Stationmaster said:

Thanks Simon - that makes perfect sense having the trap there to create a swinging overlap.  (You might even find an E10,000 circuit for that in the office archives as there was one at Reading, and possibly elsewhere).

Need to ask GX about the late Mr Powell’s “puffing the WZR”.

How about that for cryptic!!

Paul.

[St. Simon]

Controlled Intermediate Signals

 

 

Controlled Intermediate Signals, like OTAT controls in a previous post, are a very recent addition to UK signalling principles.

 

They replace the ‘Traditional’ Automatic Signal, although a Controlled Intermediate Signal (CIS) is fundamentally an automatic signal, in that it one has a single route with no moveable infrastructure within that route or overlap and no other conflict points.

 

This is an extract from my Blog, see the rest of the post here...

 

Simon

Edited August 21, 2023 by St. Simon

[The Stationmaster]

6 hours ago, St. Simon said:

Controlled Intermediate Signals

 

 

Controlled Intermediate Signals, like OTAT controls in a previous post, are a very recent addition to UK signalling principles.

 

They replace the ‘Traditional’ Automatic Signal, although a Controlled Intermediate Signal (CIS) is fundamentally an automatic signal, in that it one has a single route with no moveable infrastructure within that route or overlap and no other conflict points.

 

This is an extract from my Blog, see the rest of the post here...

 

Simon

Which represents an interesting change because it is presumably now plated as a controlled signal instead of as an automatic or semi-automatic signal and that changes the conditions under which a Driver can pass the signal when it is at danger.  So fundamentally in operational safety terms it will be very different from an automatic signal - maybe that is what has prompted the change?

[St. Simon]

10 minutes ago, The Stationmaster said:

Which represents an interesting change because it is presumably now plated as a controlled signal instead of as an automatic or semi-automatic signal and that changes the conditions under which a Driver can pass the signal when it is at danger.  So fundamentally in operational safety terms it will be very different from an automatic signal - maybe that is what has prompted the change?

Hi Mike,

 

The rule book changes in 2010 to remove the distinction between controlled and auto signals in terms of passing them at danger, so since 2010 there has really been no difference in train operation between an auto and a controlled, a driver always has to get authority to pass any signal at danger from the signaller.

 

The change to CI signals has been in response to several instances where signals have made mistakes over the use of Autos in protecting possessions, UWCs etc due to many different ways that control of an auto has been implemented over the years (dependent on region, supplier, scenario or designer).

 

So to make things consistent for the signaller, the CI Signals have been introduced so that on new works anywhere in the country, you will always, regardless of the signal type / use, set and cancel routes in the same way.

 

 Simon