Trivia: Signals That Never Show Green

Tomnick · 11 Oct 2019

ElectroSoldier said:
Am I getting mixed up....

Yes

ElectroSoldier said:
Distant?
a colour light distant can not show a red aspect.
a distant has two states, when on is means one or all of the signals in advnace of it within station limits are at danger or the signal itself has not been cleared, or if off then all the stop signals in advance of it in station limits are also off.

A 3 aspect colour light signal therefore can not be a distant. No matter how you think of it.

Others have brought good explanations of three-aspect distant signals to the party. I can think of several examples. I must point out that a distant signal 'off' means that all associated stop signals are also 'off', which isn't necessarily the same as "all signals within station limits". Various examples available again.

ElectroSoldier said:
Approach release is provided when the route in advance changes speed by 10mph or more. that can apply to one or all routes off the signal.
The speed limits are not always the same after the signal, why would you think they are?

The broad 10mph 'rule' relates to the difference between routes from the signal, not the reduction in speed approaching the junction. If you have a junction where the permissible speed on the approach is 100mph but then reduces to 70mph for both routes, you wouldn't need any form of approach control. If one route was 80mph and the other was 60mph, then you would need some form of approach control for the lower speed route. It's not always as simple as that of course!

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edwin_m · 11 Oct 2019

A distant can certainly show a green and any number of yellows but not a red.

To me a repeater is a signal whose aspect depends only on that of another signal rather than having its own separate control. But if the aspect shown is the same as the signal it repeats then it's a co-actor, which I don't recall ever seeing described as a repeater. The waters are muddied however, because a repeater may revert to its most restrictive aspect when the train passes it, even if the train hasn't yet passed the stop signal it's supposed to repeat.

So an Absolute Block distant, whether semaphore or colour light, isn't a repeater because it would have its own lever. If the box has more than one stop signal in that direction all of them would have to be clear before the distant could clear, so it doesn't repeat a specific signal either.

But an intermediate block distant arguably is a repeater!

krus_aragon · 11 Oct 2019

sw1ller said:
by that logic (and it is sound logic, but we’re talking about the railway here) then why have they not decommissioned PR19 at penmaenmawr on the up sidings or what I THINK is CR109 at Chester just before windmill lane tunnel on the down sidings. Both signals are buried in bushes and can’t have been used in 20+ years.

Isn't PR19 used by stone trains departing from the quarry? Admittedly the points for the quarry siding are a bit overgrown, but it isn't decades since it was last used...

ElectroSoldier · 11 Oct 2019

Tomnick said:
Yes

Others have brought good explanations of three-aspect distant signals to the party. I can think of several examples. I must point out that a distant signal 'off' means that all associated stop signals are also 'off', which isn't necessarily the same as "all signals within station limits". Various examples available again.

The broad 10mph 'rule' relates to the difference between routes from the signal, not the reduction in speed approaching the junction. If you have a junction where the permissible speed on the approach is 100mph but then reduces to 70mph for both routes, you wouldn't need any form of approach control. If one route was 80mph and the other was 60mph, then you would need some form of approach control for the lower speed route. It's not always as simple as that of course!

There are none Ive seen.
How can you have associated signals that are not within the station limits. Where station limits are the signals which are in control of the signal box that controls the distant?
You cant interlock a distant to a signal that it has no knowledge of.

Your example where approach control is used is not what Im talking about.
For example, approach control can be used on the signal just after Totley tunnel on the Hope Valley line as it goes into the single line section, there is a steep gradient before the signal, its used to slow trains before its released. That is where the majority of approach control signals I was talking about are used.

edwin_m said:
A distant can certainly show a green and any number of yellows but not a red.

To me a repeater is a signal whose aspect depends only on that of another signal rather than having its own separate control. But if the aspect shown is the same as the signal it repeats then it's a co-actor, which I don't recall ever seeing described as a repeater. The waters are muddied however, because a repeater may revert to its most restrictive aspect when the train passes it, even if the train hasn't yet passed the stop signal it's supposed to repeat.

So an Absolute Block distant, whether semaphore or colour light, isn't a repeater because it would have its own lever. If the box has more than one stop signal in that direction all of them would have to be clear before the distant could clear, so it doesn't repeat a specific signal either.

But an intermediate block distant arguably is a repeater!

A coacting signal isnt a repeater.
A repeater will be placed away from the signal it repeats, a coacting signal will be placed with it so that it can be seen. For instance, a signal post might have two sets of lights on it at different levels so it can be seen when coming over the brow of a hill,. A repeater always has either the prefix D or suffix R...
Signal AN.54 might have a repeater and it could be signed D AN.54 or AN.54 R.
A repeater will be placed in rear of the signal it repeats at braking distance. The actual distance will vary based on line speed.

brad465 · 11 Oct 2019

On the Chatham Mainline the two approach signals on the down slow towards Swanley (if that's the correct line name) always show restrictive aspects, with the red being at the end of Swanley platform 2. The signal goes green for Otford bound trains when the said train approaches the station, and while I haven't seen what it does for Medway bound trains it wouldn't surprise me if that was the same. What I don't get though is the line speed drops from 90mph to 30mph, regardless of which direction the train goes, so surely approach control isn't needed as a permanent AWS Magnet should exist warning of the speed restriction.

Robert Carroll · 11 Oct 2019

There is, or was, a 3-aspect signal just north of the platform on the up line at Malden Manor. The Chessington branch has two-aspect colour lights but the Epsom line is 4-aspect towards London from Worcester Park. The signal shows yellow, when the next signal protecting Motspur Park Junction is red, two yellows when the signal after that just before the level crossing immediately before Motspur Park is red but the route is clear through Motspur Park Junction itself, and green when the route is cleared through to the platform at Motspur Park. Here it is showing two yellows a few years back:

P1050276 by Robert Carroll, on Flickr

Tomnick · 11 Oct 2019

ElectroSoldier said:
There are none Ive seen.
How can you have associated signals that are not within the station limits. Where station limits are the signals which are in control of the signal box that controls the distant?

Other way around - the distant doesn’t necessarily relate to every signal in station limits. Melton’s an example - the Up distant relates to two semaphore stop signals and a three-aspect colour light, the latter acting as the distant for the section signal. You can get the distant off with the section signal still on.

ElectroSoldier said:
Your example where approach control is used is not what Im talking about.
For example, approach control can be used on the signal just after Totley tunnel on the Hope Valley line as it goes into the single line section, there is a steep gradient before the signal, its used to slow trains before its released. That is where the majority of approach control signals I was talking about are used.

Nothing to do with the gradient. You can and do get greens straight through onto the single line through Dore station with successive speed reductions from 90 (SP differential) to 70 to 55 to 50. It’s only the route around the curve to the south (15mph) that’s approach released.

SilentGrade · 11 Oct 2019

BS56 said:
That photo was taken at Aberdare station . The line went to Hirwaun to Tower colliery some four miles further down the line ! I did not know the line is now closed. The signal is a fixed red . The ground frame in the distance controlled the shunt signal to the left of the main aspect also you can see the back of a ground signal for coming off the branch.

Incidentally further along this branch toward the colliery, the google street view image for the crossing at Wellington Street shows someone, who I presume is trespassing, walking down the four foot.

ElectroSoldier · 11 Oct 2019

Tomnick said:
Other way around - the distant doesn’t necessarily relate to every signal in station limits. Melton’s an example - the Up distant relates to two semaphore stop signals and a three-aspect colour light, the latter acting as the distant for the section signal. You can get the distant off with the section signal still on.

Nothing to do with the gradient. You can and do get greens straight through onto the single line through Dore station with successive speed reductions from 90 (SP differential) to 70 to 55 to 50. It’s only the route around the curve to the south (15mph) that’s approach released.

Again you misunderstand.
I didnt say that was the arrangment on that line, I said approach control can be used in that situation, not that it is actually used on it.
I used it as an example because its a rather well known section of track.

But it leads me to ask if we are talking about never shows a green aspect though is it capable of it, or it never shows a green aspect for that routing.

ElectroSoldier · 11 Oct 2019

Another example you might be able to see Tomnick...

A train that intends to travel from the Up Ditton Slow to the Up Cheshire over the Up Hunts Cross Chord will have to use two signals to do it, the first controls the switch diamonds which are Allerton West junction, then over to the Up Ditton Fast, past the junction signal that controls access to the Up Hunts Cross Chord and on...
The signal that controls Allerton junction is an approach release because the diverging route is a lower speed than the main line. HOWEVER the signal that controls the move from the Up Ditton Slow to the Up Ditton Fast isnt but as its being routed to one that is it will never show a green aspect to a train on that particular route. If you are routed straight ahead then you can get a green aspect. It would also show a green aspect if you intend to cross over to the Up Ditton Fast and then continue straight ahead over Allerton Junction. It wouldnt show a green aspect if you are routed into Allerton TMD from the Up Ditton Slow either....

Never show a green aspect...

Oh and somebody above said there is no signal that only ever shows a red aspect without the possibility to show a proceed aspect. Yes they exist. They are called Limit of Shunt signals, and will only ever show red...
A position light, ground mounted or otherwise is still a signal.

Tomnick · 11 Oct 2019

I can’t think of anywhere where a signal is approach released solely because of a reduction in permissible speed on plain line or the ‘straight’ (i.e. fastest) route. The closest is the examples relating to moves back across to the proper line where there’s a risk that the driver might convince himself that he’s already on the proper line. I’ve half a recollection of someone mentioning a plain line example somewhere on the Southern though?

Allerton West - the move from Up Slow to Up Fast is approach released from red, isn’t it? Not done it since it was recontrolled but I’m certain that it used to be. I get what you’re saying though, but I think the OP was referring to signals that never show green for *any* route.

Last bit - not just limit of shunt indicators, either boards carrying text or in the form of a ground position light signal, but also fixed red main aspect signals. Warrington Central, Up platform in the Down direction, is an interesting one to contemplate

edwin_m · 11 Oct 2019

Tomnick said:
Other way around - the distant doesn’t necessarily relate to every signal in station limits. Melton’s an example - the Up distant relates to two semaphore stop signals and a three-aspect colour light, the latter acting as the distant for the section signal. You can get the distant off with the section signal still on.

That's possible, but only if there is full braking distance from the three-aspect colour light to the section signal. If there isn't and one of the semaphores (other than the section signal) has been replaced by a colour light for some reason then it will still be three-aspect but it will have to be showing green for the distant to be cleared. Otherwise a train could approach the colour light at yellow at full speed, too fast to be able to stop at the red. A two-aspect would have the alternative hazard that a driver may expect a route clear through the section as would normally be true with a two-aspect colour light.

ElectroSoldier said:
Oh and somebody above said there is no signal that only ever shows a red aspect without the possibility to show a proceed aspect. Yes they exist. They are called Limit of Shunt signals, and will only ever show red...

There are also fixed red main signals, which serve the same purpose but the signal leading up to them can show a main yellow aspect (as just mentioned by Tomnick). This would be used somewhere like a through station where trains can terminate by using a facing crossover on the approach and reversing in the platform, where there would be a fixed red at the far end to mark the limit of movement authority. Trains carrying passengers aren't generally allowed to proceed on subsidiary or shunting aspects, the main exception being for permissive movements into platforms.

Tomnick said:
I can’t think of anywhere where a signal is approach released solely because of a reduction in permissible speed on plain line or the ‘straight’ (i.e. fastest) route. The closest is the examples relating to moves back across to the proper line where there’s a risk that the driver might convince himself that he’s already on the proper line. I’ve half a recollection of someone mentioning a plain line example somewhere on the Southern though?

After the Eltham Well Hall derailment in the early 70s the signal on the approach was approach controlled despite only having one route. The Inspector recommended an exception to the normal rules for a very tight curve situated at the end of a very long section with no significant restrictions (driver derailed an excursion train, probably due to alcohol). I think it was mentioned somewhere on this forum that it has since reverted to standard.

Tomnick · 11 Oct 2019

edwin_m said:
That's possible, but only if there is full braking distance from the three-aspect colour light to the section signal. If there isn't and one of the semaphores (other than the section signal) has been replaced by a colour light for some reason then it will still be three-aspect but it will have to be showing green for the distant to be cleared. Otherwise a train could approach the colour light at yellow at full speed, too fast to be able to stop at the red. A two-aspect would have the alternative hazard that a driver may expect a route clear through the section as would normally be true with a two-aspect colour light.

There are also fixed red main signals, which serve the same purpose but the signal leading up to them can show a main yellow aspect (as just mentioned by Tomnick). This would be used somewhere like a through station where trains can terminate by using a facing crossover on the approach and reversing in the platform, where there would be a fixed red at the far end to mark the limit of movement authority. Trains carrying passengers aren't generally allowed to proceed on subsidiary or shunting aspects, the main exception being for permissive movements into platforms.

After the Eltham Well Hall derailment in the early 70s the signal on the approach was approach controlled despite only having one route. The Inspector recommended an exception to the normal rules for a very tight curve situated at the end of a very long section with no significant restrictions (driver derailed an excursion train, probably due to alcohol). I think it was mentioned somewhere on this forum that it has since reverted to standard.

Eltham’s the one that I was thinking of, ta!

Quite right too on the need to have braking distance from a colour light stop signal to the next signal, if the distant isn’t to apply to the latter. That is, of course, the case at Melton. There’s lots of locations that I can think of where it isn’t the case, and at most (not all), the colour light is approach released if the next signal is still at danger. I’ve never come across one where a two-aspect (R/G) colour light signal is followed by a semaphore stop signal - as you say, it’d be potentially misleading, but the Rule Book mentions it so I wonder whether there is one out there somewhere?

sw1ller · 11 Oct 2019

krus_aragon said:
Isn't PR19 used by stone trains departing from the quarry? Admittedly the points for the quarry siding are a bit overgrown, but it isn't decades since it was last used...

mom not even going to pretend I know when it was last used. Those bushes really don’t take too long to grow that big, I was just spitballing on a timeframe if I’m honest. But it does LOOK like it’s not been used in 20 years! Sorry for just generalising with the timeframes there.

sw1ller · 11 Oct 2019

Tomnick said:
Yes

Others have brought good explanations of three-aspect distant signals to the party. I can think of several examples. I must point out that a distant signal 'off' means that all associated stop signals are also 'off', which isn't necessarily the same as "all signals within station limits". Various examples available again.

The broad 10mph 'rule' relates to the difference between routes from the signal, not the reduction in speed approaching the junction. If you have a junction where the permissible speed on the approach is 100mph but then reduces to 70mph for both routes, you wouldn't need any form of approach control. If one route was 80mph and the other was 60mph, then you would need some form of approach control for the lower speed route. It's not always as simple as that of course!

a good example of this can be seen on Don Coffee’s next video at Rhyl.

ComUtoR · 11 Oct 2019

brad465 said:
On the Chatham Mainline the two approach signals on the down slow towards Swanley (if that's the correct line name)

Down Chatham Fast.

The signal goes green for Otford bound trains when the said train approaches the station, and while I haven't seen what it does for Medway bound trains it wouldn't surprise me if that was the same. What I don't get though is the line speed drops from 90mph to 30mph, regardless of which direction the train goes, so surely approach control isn't needed as a permanent AWS Magnet should exist warning of the speed restriction.

It doesn't always trip to Green. There is also a route for a 20mph speed. A permanent magnet does exist. If your going via Sole Street bank then you can get a Green. It doesn't change on approach to Swanley, there is a track circuit in the platform and trips when it activates it.

It never used to be approach controlled. Drivers used to really hammer it in to the station but there were a lot of overruns.

Hope all that helps.

edwin_m said:
I think it was mentioned somewhere on this forum that it has since reverted to standard.

Yes its back to standard, twas me who mentioned it

There is an AWS magnet provided.

ElectroSoldier · 12 Oct 2019

Tomnick said:
I can’t think of anywhere where a signal is approach released solely because of a reduction in permissible speed on plain line or the ‘straight’ (i.e. fastest) route. The closest is the examples relating to moves back across to the proper line where there’s a risk that the driver might convince himself that he’s already on the proper line. I’ve half a recollection of someone mentioning a plain line example somewhere on the Southern though?

Allerton West - the move from Up Slow to Up Fast is approach released from red, isn’t it? Not done it since it was recontrolled but I’m certain that it used to be. I get what you’re saying though, but I think the OP was referring to signals that never show green for *any* route.

Last bit - not just limit of shunt indicators, either boards carrying text or in the form of a ground position light signal, but also fixed red main aspect signals. Warrington Central, Up platform in the Down direction, is an interesting one to contemplate

There is one I just cant think of where it is.
Yes Im pretty sure its on the southern... In fact I know it is, but its gone.

Yeah, I cant remember the signal number, heading out of West Allerton on the Up Ditton Slow, towards Liverpool South you get to Allerton West Junction, if you are routed onto the Up Ditton Fast then its approach released and if you are then routed into the TMD or onto the CLC route then you are approaching another approach released signal so it wont display a green aspect.

edwin_m said:
There are also fixed red main signals, which serve the same purpose but the signal leading up to them can show a main yellow aspect (as just mentioned by Tomnick). This would be used somewhere like a through station where trains can terminate by using a facing crossover on the approach and reversing in the platform, where there would be a fixed red at the far end to mark the limit of movement authority. Trains carrying passengers aren't generally allowed to proceed on subsidiary or shunting aspects, the main exception being for permissive movements into platforms.

After the Eltham Well Hall derailment in the early 70s the signal on the approach was approach controlled despite only having one route. The Inspector recommended an exception to the normal rules for a very tight curve situated at the end of a very long section with no significant restrictions (driver derailed an excursion train, probably due to alcohol). I think it was mentioned somewhere on this forum that it has since reverted to standard.

Oh yeah.....
I remember that. There was one of those on the line that the Manchester Metro is on now... Turnback in the middle of a platform. You pulled in, terminated and faced with a red aspect at the end of the platform but you proceeded on a ground mounted position light signal.
You know I never thought of it like that... It was always on, it could not go off.

brad465 · 12 Oct 2019

ComUtoR said:
It doesn't always trip to Green. There is also a route for a 20mph speed. A permanent magnet does exist. If your going via Sole Street bank then you can get a Green. It doesn't change on approach to Swanley, there is a track circuit in the platform and trips when it activates it.

It never used to be approach controlled. Drivers used to really hammer it in to the station but there were a lot of overruns.

Hope all that helps.

Yes your track circuit comment is what I was thinking of. When you say there were many overruns could it be drivers were overestimating the slowing effect of the uphill gradient experienced on the down approaches to Swanley?

krus_aragon · 12 Oct 2019

sw1ller said:
mom not even going to pretend I know when it was last used. Those bushes really don’t take too long to grow that big, I was just spitballing on a timeframe if I’m honest. But it does LOOK like it’s not been used in 20 years! Sorry for just generalising with the timeframes there.

That's fine, I just found myself wondering if you were describing another signal in the area by mistake.

ComUtoR · 12 Oct 2019

brad465 said:
When you say there were many overruns could it be drivers were overestimating the slowing effect of the uphill gradient experienced on the down approaches to Swanley?

Nope. Pretty much just a case of driving like idiots back in the day.

Belperpete · 12 Oct 2019

As has been mentioned above, colloquially the terms repeater and distant are often confused. However, the term "distant signal" has a very specific meaning in absolute block working, in that it shows that all signals ahead controlled by that signalbox are off. It also needs its own control (e.g. lever) as there are situations where the AB Regs require the signaller to maintain the distant at caution even though all the stop signals may be cleared. If a signalbox only has one stop signal ahead, then there is little difference between a distant and a repeater, except that a distant is supposed to have its own control whereas repeaters generally do not.

Things get a bit less straight-forward where absolute block meets track-circuit block, or where you have IB signals controlled from the same signalbox. And like any rule, I suppose there will inevitably be exceptions to it!

As edwin_m mentioned, a repeater may be replaced to caution after a train has passed it, if suitable track-circuiting exists, so the repeater does not always repeat the signal ahead (the principles say that track-circuits should not be provided specifically for this purpose).

BS56 · 12 Oct 2019

Just to make things even more complex the word "Distant " may yet come back in vogue because in recent years new signalling schemes have seen signals not capable of showing a Red danger aspect are now given their own unique ID number together with the "Delta " plate ( White triangle above the number ) which begs the question can a signaller put one of these new Distants back to caution ?

edwin_m · 12 Oct 2019

BS56 said:
Just to make things even more complex the word "Distant " may yet come back in vogue because in recent years new signalling schemes have seen signals not capable of showing a Red danger aspect are now given their own unique ID number together with the "Delta " plate ( White triangle above the number ) which begs the question can a signaller put one of these new Distants back to caution ?

Modern signaling schemes have a replacement facility for every stop signal, and replacing the stop signal beyond the distant to danger would put it back to caution without the need for a separate control on the distant.

matchmaker · 14 Oct 2019

I have recently discovered that some resignalling at Fouldubs Junction on the Grangemouth line has resulted in the home signal becoming a fixed semaphore stop signal.

ElectroSoldier · 15 Oct 2019

BS56 said:
Just to make things even more complex the word "Distant " may yet come back in vogue because in recent years new signalling schemes have seen signals not capable of showing a Red danger aspect are now given their own unique ID number together with the "Delta " plate ( White triangle above the number ) which begs the question can a signaller put one of these new Distants back to caution ?

Repeaters can be prefixed D or have a suffix R

Tomnick · 15 Oct 2019

ElectroSoldier said:
Repeaters can be prefixed D or have a suffix R

I’ve never seen one prefixed ‘D’ on the strength of it being a distant signal (as opposed to it being the prefix for the controlling box!), but plenty with an ‘R’ prefix.

ComUtoR · 15 Oct 2019

Prefix D/R is historical, probably a few floating about somewhere. Not part of the new standards for identification plates. (that I'm aware of)

rower40 · 15 Oct 2019

BS56 said:
Just to make things even more complex the word "Distant " may yet come back in vogue because in recent years new signalling schemes have seen signals not capable of showing a Red danger aspect are now given their own unique ID number together with the "Delta " plate ( White triangle above the number ) which begs the question can a signaller put one of these new Distants back to caution ?

edwin_m said:
Modern signaling schemes have a replacement facility for every stop signal, and replacing the stop signal beyond the distant to danger would put it back to caution without the need for a separate control on the distant.

As always, there's an exception! T6245 on the Down Sunderland at Brockley Whins is a repeater (shows single-yellow, double-yellow, green), but it has a replacement facility and a TD berth. I've no idea why.

ElectroSoldier · 15 Oct 2019

ComUtoR said:
Prefix D/R is historical, probably a few floating about somewhere. Not part of the new standards for identification plates. (that I'm aware of)

Yeah but Ill bet there is one or two still out there.

edwin_m · 16 Oct 2019

ComUtoR said:
Prefix D/R is historical, probably a few floating about somewhere. Not part of the new standards for identification plates. (that I'm aware of)

I think R as a suffix is still quite common. If I recall correctly a new distant or repeater will get its own number.

Trivia: Signals That Never Show Green

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