Why are many LED signal varieties being introduced?

[brad465]

As many know and have seen, the rise of LED signals with multi-aspect lights has come about over the last decade and possibly earlier, but I've noticed that as technology improves new varieties and older ones seem to be being rolled out together, which I think is odd as I would have thought in most places one or two varieties would be enough.

Variety examples I know of include (with image links):

-The "standard" type with one or two lights and a shade over each
http://www.deathbyhealthandsafety.co.uk/safetyvalve/manormachine.html

-Same as above but on a simple pole with no ladder and/or caging around (2nd picture)
https://www.flickr.com/photos/buzz68/15658807887


-A flat board with no shades and many small LED lights on the board visible if you look close enough

-Like the older one light for each aspect but in new LED form
http://collis.uk/signal-house/

-Others?

The main question I have is why these all appear to be being installed on different parts of the network together for different places, rather than just using one or two types for all new installations???

 

[TheManBehind]

I imagine it's likely to be down to who can supply what at the most appropriate price for a large number of signals, however signal sighting plays a large part. The second one in the list is used where sighting can be an issue if a full-size signal is used - the compact size makes it useful (there's a few on Wessex, I believe round the Hounslow loop).

 

[brad465]

Yes as a regular user of the GWML this year I've seen the whole lot variety wise installed, while London Bridge and East Kent phase 2 have been the standard only, among others.

If I'm right the latest signalling on the GWML from Reading to London may not last long along most of the route in light of planned cab-signalling for Crossrail.

 

[gsnedders]

If I'm right the latest signalling on the GWML from Reading to London may not last long along most of the route in light of planned cab-signalling for Crossrail.

ETCS Level 2 as rolled out on the GWML will still have line-side signalling. (Of course, being ETCS Level 2, equipped stock will have an in-cab display of the signalling.) In comparison, the ECML won't have line-side signalling, so only ETCS Level 2 equipped stock will be able to run on it.

 

[alxndr]

Some are retrofitted into old signal heads, which in theory saves replacing the whole thing.

Some new signals are being installed where they no longer require anyone to go up the signal head at any point, one example is the Dorman Lightweight Winch Signal shown in your second link, although there are other offerings using various lowering methods such as springs. A good reason to install signals which can be lowered is health and safety, particularly with overhead lines, and of course working at height.

 

[swt_passenger]

I think another factor is that hardware for a project can be bought and stored months or years before it is needed, and stockpiled for that particular project. If that job is delayed significantly, as some re-signalling projects have been, then you end up with a new installation with apparently older equipment.

IIRC a few years ago one of the major projects in the south was installing conventional signals at the same time as LEDs were being installed nearly everywhere else?

 

[MarkyT]

IIRC a few years ago one of the major projects in the south was installing conventional signals at the same time as LEDs were being installed nearly everywhere else?

Was that Portsmouth resignalling? The Siemens 'Simis W' technology employed there was unable to drive the new LED heads, so modified standard UK heads with incandescent lamps were used. See page 3 of the leaflet here for an illustration of the earlier Bournemouth scheme using the same tech - A SWT VEP speeds past a fairly standard UK 3-aspect signal. Siemens was initially preferred for, but later lost, East Kent Resignalling and following this setback they quickly abandoned trying to adapt their standard German products for UK. Soon however, they re-entered the British market by acquiring the rail assets of Invensys, including the famous Westinghouse signalling business, Siemens are now able to offer the former Westinghouse range of UK SSI derivative products with standard interfaces able to drive any of the LED heads now available.

 

[edwin_m]

Was that Portsmouth resignalling? The Siemens 'Simis W' technology employed there was unable to drive the new LED heads

SIMIS-W was also used at Bournemouth I think.

 

[D Foster]

As far as I am aware LED signals have always been complete new heads - even when they look quite like old-style heads from the front (except- of course - for the LED pattern as distinct from the old0style lens).

While I understand that some lamp cases on semaphore signals have had LED lights inserted to replace earlier lights I am not aware that any old style (filament lamp) Colour Light signals have had - or even could have - an LED light source fitted into the housing.

As far as I am aware all the LED replacements and new signals are complete new LED heads. Can anyone conform or correct this please?

One thing that the OP will be seeing is that some replacement heads have been in Multiple Aspect format (for example some VMS signals) while others (mainly Dorman or Signal House - but also some VMS - the flat-faced ones with the small repeaters on the side of the head) have been Searchlight Signals.

I notice that the Dorman searchlights often have a back board that copies the previous multiple aspect back board even though a large part of the board is effectively redundant - except to maintain a silhouette and/or overall appearance. However; this isn't always the case and some "single cluster" multi-colour LEDs only have a small backboard.

No ladder and cage is, as I understand it, a factor of the longevity of LEDs compared to the previous filament lamps. There are also H&S / working at height considerations - plus - no ladder provision is more secure from vandalism - there is no need for a gate to be (retro-)fitted to stop unauthorised persons climbing the signal.

The Dorman "Lollipop" signals are also "plug and play" - the post and head simply lift out of the base element.

Why different types? That's simple - this is the railway! Why have one type when you can have half a dozen?

I'm not sure who made them but I believe that the first - or very early - LED main signals came from Australia and/or were to an Australian specification. (I would be interested to know when and where the first ones appeared please...) I am told that the Australian ones had no provision for our cold climate with a result that temperature changes experienced her also meant that the LEDs had a problem with changes to the exact colour of the aspect... Can anyone confirm this please?

Further (if I may be forgiven) I have been told that the Ansaldo (spl?) signals between Crewe and Cheadle are "the wrong colour". Can this be confirmed or corrected please?

Thanks

 

[Signal Head]

As far as I am aware LED signals have always been complete new heads - even when they look quite like old-style heads from the front (except- of course - for the LED pattern as distinct from the old0style lens).

While I understand that some lamp cases on semaphore signals have had LED lights inserted to replace earlier lights I am not aware that any old style (filament lamp) Colour Light signals have had - or even could have - an LED light source fitted into the housing.


As far as I am aware all the LED replacements and new signals are complete new LED heads. Can anyone conform or correct this please?

Howell's make something called a 'Light Engine' which is a LED replacement for an SL35 (standard lamp used in conventional heads). These can be distinguished by the fact that the change of aspect is instant, as there is no thermal lag. Also, the Green aspect colour is noticeably bluer that a filament, as the inner lens isn't having to correct the yellowish light from a filament.

One thing that the OP will be seeing is that some replacement heads have been in Multiple Aspect format (for example some VMS signals) while others (mainly Dorman or Signal House - but also some VMS - the flat-faced ones with the small repeaters on the side of the head) have been Searchlight Signals.

I'm not aware that Signal House have a design with a common aperture. The VMS multi-aperture heads are distinctive in having no hoods, instead they have a lens with an angled face.

Further (if I may be forgiven) I have been told that the Ansaldo (spl?) signals between Crewe and Cheadle are "the wrong colour". Can this be confirmed or corrected please?

The yellow aspect is a slightly different colour to a UK filament head, I'm not sure you could describe it as the 'wrong' colour though. I believe there were objections from drivers when the scheme was underway, and I also think an interface to allow use of Dorman LED heads has been developed, but whether any Ansaldo heads have actually been replaced is another matter. These aren't LEDs BTW, but use an optical arrangement to show more than one colour through a single aperture.

 

[MarkyT]

No ladder and cage is, as I understand it, a factor of the longevity of LEDs compared to the previous filament lamps.

Unless a lightweight supporting structure can be hinged down to ground level for maintenance, LED signals still need access for periodic lens cleaning and light intensity testing. With the reduced frequency of routine visits however and the large reduction in unexpected failure compared to filament lamps, alternative access methods avoiding the expensive ladders and walkways can be considered such as a rail mounted mobile work platform. I'm not aware if this has been implemented anywhere, but that solution's obvious disadvantage is that the line needs to be closed under a possession to get the work platform into place.

Why different types? That's simple - this is the railway! Why have one type when you can have half a dozen?

Many suppliers means price competition. If there was only one approved manufacturer they'd be able to charge what they want!

I'm not sure who made them but I believe that the first - or very early - LED main signals came from Australia and/or were to an Australian specification. (I would be interested to know when and where the first ones appeared please...)

I found this leaflet from an antipodean outfit called Aldridge, and they claim to have introduced LEDs to rail there in 1995, well before UK. It's certainly possible some of their products may have been imported for evaluation.

I am told that the Australian ones had no provision for our cold climate with a result that temperature changes experienced her also meant that the LEDs had a problem with changes to the exact colour of the aspect... Can anyone confirm this please?

Don't know about the Aussie ones, but I remember reading the first Dorman UK design took a long time getting product approval from Railtrack / Network Rail because of poor color temperature stability of the yellow in particular under varying conditions. Some clever design changes overcame the issue eventually, including directing heat from the driver board over the array to help manage the temperature.

Further (if I may be forgiven) I have been told that the Ansaldo (spl?) signals between Crewe and Cheadle are "the wrong colour". Can this be confirmed or corrected please?

As far as I know, the South Manchester scheme by Ansaldo is the only case in recent years of a supplier introducing an entirely unmodified continental head design into the UK. By contrast, instead of attempting to introduce standard German signal head products for concurrent projects in the south, Siemens adopted standard UK filament lamp heads with a small wiring modification to suit their different 1st/2nd filament switching and failure alarm circuits.
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When I was a young trainee in the mid 1980s I spent some time in the old Western Region Technical Investigations lab at Reading (now long gone). One of my projects there was to construct a prototype red LED array for a level crossing boom lamp application. Filament lamps in that application were notoriously unreliable due to the constant movement and vibration of barriers rising, lowering, shaking in the wind etc, so it was seen as a very obvious first candidate for LEDs. I left the board on an extended soak test, and many months after my attachment there concluded I recall seeing it every day still shining out of the lab window.

 

[pompeyfan]

Are the signals on the westbury-Salisbury line retrofitted into old style heads?

 

[Deepgreen]

Howell's make something called a 'Light Engine' which is a LED replacement for an SL35 (standard lamp used in conventional heads). These can be distinguished by the fact that the change of aspect is instant, as there is no thermal lag. Also, the Green aspect colour is noticeably bluer that a filament, as the inner lens isn't having to correct the yellowish light from a filament.

Indeed, and they are in use in large numbers. I find all the aspects to be of a more intense colour, aside from their instant change characteristic.

 

[Walnut_rede]

As an inmate of the old Western Region TIC I can just about remember some of our early experiences with LEDs for signalling purposes. The main problems were reliability and the colours not displaying properly, bluish tints I think. However the one piece of LED equipment we found that worked perfectly, was cheap(in railway signalling terms) and was almost bulletproof was the tail lamp that had replaced the old oil lamps on the back of trains. So we acquired one and used it, or at least it's circuitry, to inspire our efforts.

 

[MarkyT]

However the one piece of LED equipment we found that worked perfectly, was cheap(in railway signalling terms) and was almost bulletproof was the tail lamp that had replaced the old oil lamps on the back of trains. So we acquired one and used it, or at least it's circuitry, to inspire our efforts.

Another great early LED application, as tail lamps are also subject to much vibration and shock. I don't know if filament lamps had ever been tried in tail lamps but I'd guess they would be very unreliable and that's no doubt why oil lamps survived so long. Rather like semaphore signal lamps. Many of those survived as oil right up to their replacement by LEDs in recent years.

 

[Railsigns]

I don't know if filament lamps had ever been tried in tail lamps

They certainly have been. The earliest kind I remember looked like this, with two red lenses:

In the early 1980s, there were some quite fancy electric tail lamps on trial, from two separate manufacturers (Adlake and Lydd).