Signal questions

[waterlooroader]

Forgive my ignorance with the following questions, but I was just wondering:

1. If a signal is not displaying an aspect (For example if vandalism had caused the bulb to break) would the driver assume that the signal was set to danger, stop and call the signalman for advice?

2. I presume that mobile phones are not permitted whilst the driver is driving, but would it be acceptable to use a mobile to call the signalman if the signal phone and radio were out of action? Having said that, if the radio was out of action, would that qualify as a technical fault leading to the termination of the service?

3. When a driver passes a signal at danger on the advice / authority of the signalman, does this need to be recorded, either by the driver or signalman?

Thanks in advance

 

[Cherry_Picker]

1] Yes

2] Yes and almost certainly yes.

3] Yes, and it is automatically recorded at the signalman's end.

 

[Railsigns]

1] Yes

Unless it's a distant signal, in which case the driver must treat it as though it's displaying a caution aspect.

 

[Cherry_Picker]

Of course. Still report it ASAP though.

 

[Llanigraham]

1] Yes

2] Yes and almost certainly yes. BUT THE DRIVER COULD GET OUT OF THE CAB AND WALK TO THE SIGNAL BOX, IF APPLICABLE, IN THE MEAN TIME.

3] Yes, and it is automatically recorded at the signalman's end. AND NOTED IN THE TRB.

 

[TomBoyd]

3] Yes, and it is automatically recorded at the signalman's end. AND NOTED IN THE TRB.

You wouldn't necessarily note down in the TRB every signal passed at danger. In fact, barely any situations would necessitate that.

 

[Llanigraham]

You wouldn't necessarily note down in the TRB every signal passed at danger. In fact, barely any situations would necessitate that.

Sorry, but in our area we are told to note the TRB.

 

[t o m]

bulb

Lamp!

 

[Muzer]

Further to your first question, do signals have some positive confirmation that current is flowing so that the interlocking can set the previous signals to caution as appropriate if a filament blows or whatever, or what? I'd be surprised if they don't.

 

[andy19_64]

Occasionally a driver will get a change of aspect on the signal in front of him like yellow-red-yellow and this will not get detected on the signallers panel so to him everything is fine.

 

[Llanigraham]

Further to your first question, do signals have some positive confirmation that current is flowing so that the interlocking can set the previous signals to caution as appropriate if a filament blows or whatever, or what? I'd be surprised if they don't.

Depends on whether you are talking about semaphores or coloured light.
Semaphores don't.
Interlocking is more mechanical than electronic.

 

[Crossover]

Further to your first question, do signals have some positive confirmation that current is flowing so that the interlocking can set the previous signals to caution as appropriate if a filament blows or whatever, or what? I'd be surprised if they don't.

From a conversation I had with someone the other week, I believe in colour light signals there is a backup filament (to avoid a blank aspect) which should trigger an alert to the signaller. Not surewhat indications there are of failed LED's though ( but I imagine you could lose a certain number in a cluster before it became problematic)

 

[Bodiddly]

Further to your first question, do signals have some positive confirmation that current is flowing so that the interlocking can set the previous signals to caution as appropriate if a filament blows or whatever, or what? I'd be surprised if they don't.

Thinking back to my S&T days, our section was a Solid State Interlocking. Signal lamps have a main and a secondary filiment, when the main burns out, the secondary automatically kicks in. As this happens the state of the interlocking changes, and the signal number and main filiment fault shows up on the technicians terminal. This was checked every day for main filiment failures. These would be recorded and the bulb changed the next time the area was visited on a maintenance turn. Each filiment had an 8000 hour lifespan so there was no rush to change the bulb. Although it never happened on my shift, I seem to remember that if the bulb was to lose both filiments, the signal in rear would return back to a red aspect, meaning a driver should never draw up to a signal not showing an aspect.
I may be wrong about this as it was a few years ago!

 

[carriageline]

You wouldn't necessarily note down in the TRB every signal passed at danger. In fact, barely any situations would necessitate that.

Careful mate, you have only just finished signalling school and your already telling more, actually never mind more, telling experienced signallers what to do/what they are doing is wrong! Your gonna be popular!!

Our place also requires signals talked past to be recorded

 

[t o m]

If a signal is not proven to be lit then the signal in rear will go to it's most restrictive aspect. Sometimes a signal may be lit but appear black on the panel if the lamp is not drawing enough current to operate the proving circuit.
If it is an auto signal the signaller is unable to tell what aspect is being displayed either way. If there is a COA then the signaller is likely to see it on his panel if it was red vice yellow but not yellow vice green as to him a proceed aspect, green or yellow, appears as a just a green on the panel.
Most lamps have been replaced with LED light engines which obviously don't have an auxiliary filament.

 

[Tomnick]

Depends on whether you are talking about semaphores or coloured light.
Semaphores don't.
Interlocking is more mechanical than electronic.

Some semaphores have lamp repeaters (even paraffin-lit examples!), which sometimes form part of the block controls (i.e. home signal must be proved alight before a line clear can be given). Lamp repeaters often aren't provided, of course (if the signal's clearly visible from the box, for example), but they're certainly not uncommon.

Just a couple of notes to add to the replies dealing with colour-light signals - in most cases, the stop signal in rear will be held at danger, but some earlier installations allowed the signal in rear to clear to a yellow instead, I understand. Also, in many cases now, a TPWS failure is indicated through the lamp proving circuit, so you don't know at first whether it's a black signal or just a TPWS failure.

 

[DJL]

So if the green lamp fails would the signal automatically show a yellow or double yellow instead?

 

[Nippy]

No, signal in rear would revert to red.

 

[Tomnick]

So if the green lamp fails would the signal automatically show a yellow or double yellow instead?

Not normally, unless some of the newer installations revert to a more restrictive aspect. It's usually possible for the signalman to achieve the same effect by trying to avoid any indication that requires the expired lamp though.

 

[glbotu]

In the event of a signal failure, where it was not possible to route trains differently, what would be the standard procedure? Would every driver be talked through or would the service be suspended?

 

[carriageline]

In the event of a signal failure, where it was not possible to route trains differently, what would be the standard procedure? Would every driver be talked through or would the service be suspended?

Trains would be talked past both signals, but there would probably be diversions elsewhere and other things in place. Not sure about suspension, as it's hardly a "major" problem, and S&T shouldn't take too long to sort it. But who knows, that's up to the controls to decide! A unlit signal wouldn't cause too much delay to each delay, on the grand scheme of things.

 

[Pilgrim]

Also, in many cases now, a TPWS failure is indicated through the lamp proving circuit, so you don't know at first whether it's a black signal or just a TPWS failure.

Some TPWS occurrences are put through the aspect proving and will show lamp out but others show either a flashing blue light or flashing blue square (depending on system) which is the preferred option

 

[Tomnick]

Indeed, it's far preferable to have a separate indication; my understanding is that it's only shared with the lamp proving on older installations where there's no easy way of providing separate TPWS indications.

 

[Llanigraham]

If a signal is not proven to be lit then the signal in rear will go to it's most restrictive aspect. Sometimes a signal may be lit but appear black on the panel if the lamp is not drawing enough current to operate the proving circuit.
If it is an auto signal the signaller is unable to tell what aspect is being displayed either way. If there is a COA then the signaller is likely to see it on his panel if it was red vice yellow but not yellow vice green as to him a proceed aspect, green or yellow, appears as a just a green on the panel.
Most lamps have been replaced with LED light engines which obviously don't have an auxiliary filament.

Does not apply to semaphore signals, does it?

 

[edwin_m]

Shouldn't you have a lamp repeater for any semaphore where the lamp or its backlight isn't visible from the box? As I understand it, this repeater doesn't do anything clever, it is down to the signalman to arrange for approaching trains to be cautioned if the lamps aren't lit when they need to be.

 

[Llanigraham]

We have a "filament out/power out" alarm only. No repeaters.

T o m's comment I quoted seems to be totally about coloured light signals.

 

[Lockwood]

What would happen if a semaphore lost its arm by some means? (weather damage, vandalism, little green men beaming it up whatever)
The automatic protection mentioned for colour lights wouldn't work here, I'm guessing.

Would it be treated the same if the whole arm was gone or just the sticking out bit, with the spectacles remaining?

And if the rodding froze/got jammed with the signal showing a proceed aspect (ie the physical link to the box doesn't want to move when the signaller tries to revert the signal to danger?)

 

[Tomnick]

You wouldn't necessarily know if just the blade was missing, leaving the spectacle plate and mechanical grubbing intact, until someone stopped to report it! I suppose you'd be able to work normally in darkness though, as the nighttime indications would remain. If the spectacle plate went missing too, you'd know about it, as that's what the arm detection is attached to. The latter serves to indicate the position of the arm where the signal's not visible from the box (and sometimes, for example if the block controls check that the home signal is at danger before allowing a 'line clear' to be given, even if it's clearly visible), so you know either by that or by direct observation if a signal failed to return to danger.

 

[Lockwood]

If the driver saw the blade was missing but was expecting it to be clear from the distant signal, would they have to stop the train immediately at the signal and notify you or do it as soon as reasonably practicable?

 

[MarkyT]

Semaphore signals not directly visible from the signal box, in addition to lamp proving, have electrical arm proving as well, achieved by a contact box connected to the spectacle plate casting. Indication in the box is a 3 state ON/WRONG/OFF needle pointer unit or a group of lamps conveying the same. Block controls in order for a successful line clear to be sent usually require arms of home and distant signals to be proved ON and ALIGHT by relays wired in series with the indicators. The indications can't prove the entire arm and spectacle plate assembly is complete however, but do give reasonable confidence there is a working arm attached to the signal post within acceptable limits of adjustment.