LED Signals

[ComUtoR]

Top left all the way. The rest are a bit fugly. Is there any practical reasons for not having a hood ? Is there any sighting differences between them (sunlight/glare etc) ?

 

[Crossover]

Dorman signals at the top; VMS at the bottom.

Lightweight models on the right.

Thanks Railsigns!

It'll be the Dorman Lightweights on the Toddy Curve then. I have also seen the "heavy" VMS ones before - is the wire mesh there to help close up visibility?

Top left all the way. The rest are a bit fugly. Is there any practical reasons for not having a hood ? Is there any sighting differences between them (sunlight/glare etc) ?

Can't disagree with that appraisal!

 

[edwin_m]

Top left all the way. The rest are a bit fugly. Is there any practical reasons for not having a hood ? Is there any sighting differences between them (sunlight/glare etc) ?

VMS is presumably the company behind Variable Message Signs, the LED signs on the motorway that seem to be easily visible in all lighting conditions without needing hoods.

 

[HarleyDavidson]

There's a real weird one at Dorking. The home signal is seemingly an all plastic affair with a dummy (calling on signal) built into it!

I can't wait to see how long these plastic signals for a now plastic railway, last after a few years of beatings from the UK weather, will it wilt under 90° of heat or will it snap under -20° of cold and strong winds?

 

[D Foster]

What you refer to is called "approach lighting", approach control being something else entirely.



Yes, it was frequently done in the UK to conserve battery power in outlying areas. Nowadays, where approach lit signals exist (there are about 30 of them in Scotland), it is for sighting reasons.

Thanks for the correction. I should have known that. (Excuse - a long time since I looked at that subject :cry: )
--- old post above --- --- new post below ---
Thanks for the pictures

Any chance of a pic of the Ansoldo's?

The "weird signals with a position light built in" (to paraphrase) are variations of the Dorman lightweights I believe.

 

[Railsigns]

Any chance of a pic of the Ansoldo's?

It's Ansaldo, with an A in the middle.

There's a photo at the bottom of the page here.

 

[LowLevel]

There's a real weird one at Dorking. The home signal is seemingly an all plastic affair with a dummy (calling on signal) built into it!

I can't wait to see how long these plastic signals for a now plastic railway, last after a few years of beatings from the UK weather, will it wilt under 90° of heat or will it snap under -20° of cold and strong winds?

There's loads of similar ones on the GN/GE Joint line, lightweight modular signalling. They look a bit weird.

One I've never been able to work out is why, in the middle of an mostly/entirely Dorman area, the first signals on the up on the Erewash once the up/down Blackwell Goods has appeared at Morton Junction between Chesterfield and Alfreton are a pair of those so called VMS heavyweight style things (new LED heads with 4 separate apertures). There aren't any others on the 400 odd miles of railway that I sign.

My preference is for the LED replacement light engine things in the more traditional signal heads personally.

I dispatch trains off most types of starting signal and they've got the best compromise between being visible and being blinding.

 

[D Foster]

It's Ansaldo, with an A in the middle.

There's a photo at the bottom of the page here.

Thanks for the pic I have slapped my spelling fingers for being naughty.

I know that signal! I wish I could catch it (or its friend across the line) with that display showing!!!



Has anyone done anything, or is any system in place these days, for reporting some of the issues with these signals?

Thinking of "issues" (other than train despatch) I haven't yet seen any of these new beasties with a sighting board/back board... Ummm... Except - I think - one at Nuneaton at the bottom of the slope - which is to block off the view of headlights on vehicles on the adjacent roundabout.

 

[hulabaloo]

Yes I experience the 2 yellows merging into 1 yellow at night from a distance, this is due to the brightness and the 2 lenses are closer together than older colour lights.

Would a green and yellow combination improve this situation? What would be the pitfalls of using this instead?

 

[driver_m]

Would a green and yellow combination improve this situation? What would be the pitfalls of using this instead?

ETRMS isn't that far off now so it's probably not worth the inevitable problems that would be caused by it, failure situations if one colour failed for instance. And so on.

 

[hulabaloo]

That's fair enough although I can't see ETRMS being implemented in the SE network this century. Can LED lights fail in such a fashion?

 

[scott118]

Would a green and yellow combination improve this situation? What would be the pitfalls of using this instead?

on the same signal post? Route knowledge will tell you what aspect signalling you are running under, should the LED's appear to 'bleed', two into one..

 

[cool110]

Green-yellow is used in Japan, with double yellow meaning the opposite over there.

 

[infobleep]

Nope, they just get covered up with snow. Good eh?

There's a solution to this. Bring back for signalmen but only use them for snow conditions.

 

[MarkyT]

Green-yellow is used in Japan, with double yellow meaning the opposite over there.

To be clear I think you mean a double yellow YY is MORE cautious than a single yellow Y in Japan, i.e it can be seen seen as the last cautionary aspect before encountering a red, whilst in UK YY is less cautious than Y. In most cases in Japan however the last caution before a red is actually Y, with the YY only used rarely for special cases where there is an especially short block on approach to the red or a shorter than normal overlap beyond the red.

See https://youtu.be/Fez7f70sBDE?t=1m16s for an illustration of typical aspect sequence, which is a '4-aspect' system in most cases, with yellow green (YG) as preliminary caution instead of our YY.

In UK YY, the top yellow lamp is not proved to be alight in order to display a proceed at the previous signal. The idea is that if the top yellow is extinguished under fault conditions, the driver will still see a single yellow, which is more cautious and should result in a more severe slow down than necessary in response. That's also the argument for double yellows merging into one at a distance. if they are perceived as one lamp then more severe corrective action will be taken, so it's fail-safe.

 

[swt_passenger]

... and the 2 lenses are closer together than older colour lights.

Isn't the gap between the two LED units meant to replicate the spacing on an equivalent four aspect conventional signal?

That seems to be how they show it on the various manufacturers web sites. They definitely aren't right next to one another.

 

[455driver]

Isn't the gap between the two LED units meant to replicate the spacing on an equivalent four aspect conventional signal?

That seems to be how they show it on the various manufacturers web sites. They definitely aren't right next to one another.

and they definitely not as far apart as they would be if there was another aspect in between them!

They are supposed to be but most aren't, we have a couple of locations where we go from 3 aspect to 4 and the first 4 aspect is a bleeder so it's difficult to see if it's a single or double yellow, I have reported it a few times but nothing happens because 'it meets the required standard's which seems to be the default answer to any reports we put in.

 

[ilkestonian]

Pretty serious compromise isn't it! Might change their attitude when a driver misses out one and ends up in the back of another train.

Isn't that what AWS and TPWS is for?

And what about route knowledge?

 

[najaB]

They are supposed to be but most aren't, we have a couple of locations where we go from 3 aspect to 4 and the first 4 aspect is a bleeder so it's difficult to see if it's a single or double yellow...

I suppose, as MarkyT said above, 'they' see it as not being a problem because if you can't tell that it's double yellow you'll have to treat it as if it was single - so you might end up running slow but there's no danger.

 

[cool110]

Isn't that what AWS and TPWS is for?

And what about route knowledge?

AWS doesn't help as that can only tell if the signal is green or not and TPWS only come into play when it's too late.

As for route knowledge, it won't help if both are possible or if a signal gets put back for any reason.

 

[carriageline]

That's fair enough although I can't see ETRMS being implemented in the SE network this century. Can LED lights fail in such a fashion?

Thameslink core will have it in 2 years time! Depending how well that goes will see how fast it spreads I suppose.

 

[theageofthetra]

This issue of two LED yellows being misread as single yellow must have far more of an impact on high speed lines than in a metro environment. I accept that it complies with group standards as you would slow to a greater extent, but when the DAB (delay attribution) reports go in with it on as a cause and the costs rack up perhaps it will be taken more seriously?

 

[QueensCurve]

Dorman signals at the top; VMS at the bottom.

Lightweight models on the right.

The bottom left signals have been installed for a few years in Lancaster.

These are true to the original signals in providing a "binary number" indication, not just a colour.

I would have thought this type would be better from a human factors perspective?

 

[MarkyT]

This issue of two LED yellows being misread as single yellow must have far more of an impact on high speed lines than in a metro environment.

The Unipart Dorman is the most popular LED type in the long range 'searchlight' form, so for a 4-aspect installation there is a lower unit which can display R,Y or G and a simpler, cheaper unit above that can only display Y. Historically in UK, there were many searchlight form signals using filament lamps and movable coloured filters behind a conventional fresnel lens, particularly on the Eastern Region ISTR, and the four-aspect version was arranged in a similar way with a blank space between them to properly separate the two elements of a YY aspect display. From old photos the historic signal lenses in these seem to be more widely spaced, but the 'bleed' effect in the modern signal may be partly due to the Dorman design having slightly larger lens apertures than than many traditional designs, as well as having a more uniform light output across the 'cone of light' eminating therefrom. The lens centres may be arranged at a similar centre spacing to older units, but their outer edges could be closer.

I compared drawings for a Dorman searchlight:
http://www.unipartdorman.co.uk/assets/4_aspect_lu.pdf

and another modern LED product but with individual lens units, The Signal House Ltd design:
http://collis.uk/pdf/SS4001-A.pdf

The units of the Dorman design are arranged at 500mm centre spacing, whilst the Signal House has 255mm between each unit resulting in 510mm between the two yellows.

The Dorman lens diametrer is shown as 230mm. That's not show on the Signal House drawing, but the units appear to be packed in very close together so I doubt there's much difference in diameter.

Looking at photos of more recent filament head designs the lens diameter doesn't seem to be much different to the Signal house design, but in much older models particularly the old LNER searchlights the two lens are either more widely spaced or are a smaller diameter (or both).

http://www.unipartrail.com/assets/led-signalling-handbook-(1).pdf

The bottom left signals have been installed for a few years in Lancaster.

These are true to the original signals in providing a "binary number" indication, not just a colour.

I would have thought this type would be better from a human factors perspective?

Maybe close up if you're colour blind

Long range you can't determine which lens the light is coming from on the head, so it's separation that is more important for correctly identifying the YY. The Pensilvannia RR in USA stuck with position light indications for their main line signals long after most others had switched to colour light. They reasoned that from a human factors POV, shape and movement was more obvious than colour and changes to colour. Their light signals are similar in appearance to our UK loading/unloading signals often seen at Power stations and pits (not much now though!)

 

[Railsigns]

The units of the Dorman design are arranged at 500mm centre spacing, whilst the Signal House has 255mm between each unit resulting in 510mm between the two yellows.

The Dorman lens diametrer is shown as 230mm. That's not show on the Signal House drawing, but the units appear to be packed in very close together so I doubt there's much difference in diameter.

Looking at photos of more recent filament head designs the lens diameter doesn't seem to be much different to the Signal house design, but in much older models particularly the old LNER searchlights the two lens are either more widely spaced or are a smaller diameter (or both).

The descriptive leaflet for the MV-GRS Type SA 4-aspect searchlight signal shows the two lenses spaced at 24" (609.6 mm) between centres. The outer lenses are 8 3/8" (212.7 mm) diameter.

 

[edwin_m]

The dimensions of signal heads have been defined in a Group Standard in recent years, so it's likely the LED ones will have the same basic dimensions as their filament predecessors. Besides if, for example, the spacing between the two yellows was increased then the top one might go out of view under certain circumstances. Hence a new sighting committee might be needed for what would otherwise be a simple swap of signal heads.

 

[Taunton]

What you refer to is called "approach lighting", approach control being something else entirely. Yes, it was frequently done in the UK to conserve battery power in outlying areas. Nowadays, where approach lit signals exist (there are about 30 of them in Scotland), it is for sighting reasons.

The initial "searchlight" signals often employed approach lighting in remote areas. The first users were the LNER, who imported the units from GRS (General Railway Signal Corp) in the USA, where approach lighting was, and to an extent continues to be, used to conserve battery power supply. In fact, in the USA you can see whole gantries of junction signals all dark until a train approaches. This is often in conjunction with arrays of solar battery chargers mounted alongside. On single lines the signals for both directions will switch on. This has the advantage over conventional signal lighting that staff on the ground get a warning that an oncoming train is getting close.

Gerry Fiennes, in his book on railway management, wrote that there was a distant on the straight Spalding to March line whose operating track circuit was rather close in, so it didn't switch on until well after it came into sight, and crews used to take bets on what it was going to show. Distants, beyond the operating distance for a wire pull from the signalbox, were for quite some years the main usage for searchlights in Britain, particularly on the LNER. The GWR favoured battery-powered distant semaphores in the same situation, sometimes mounted slotted with a conventional wire-pull starter for the previous signalbox on the same post.

 

[TDK]

The LED signals are an improvement on the SL signals - the only problem I find is at request stops with a starter, you just cannot make out if there is anyone on the platform until you are at the platform end - Llanfair PG is a typical example on the up and being only a very short platform the LED signal blots out the view of the platform at night. As for a signal being obscured by snow this won't be a problem as you would have had a caution before and if that is blocked by snow the AWS will warn you that the signal is not displaying a green aspect.

 

[miami]

The LED signals are an improvement on the SL signals - the only problem I find is at request stops with a starter, you just cannot make out if there is anyone on the platform until you are at the platform end - Llanfair PG is a typical example on the up and being only a very short platform the LED signal blots out the view of the platform at night. As for a signal being obscured by snow this won't be a problem as you would have had a caution before and if that is blocked by snow the AWS will warn you that the signal is not displaying a green aspect.

If the signal isn't needed (can be covered in snow without problem), why have signals in the first place?

 

[najaB]

If the signal isn't needed (can be covered in snow without problem), why have signals in the first place?

A signal head covered by snow isn't necessarily an immediate safety threat (since passing anything other than a green aspect will trigger a AWS/TPWS indication/intervention) but it would bugger up the timetable if every train was to grind to a halt on passing a double/single yellow.