Flashing platform repeaters

[1018509]

In this video:-



from the Metropolitan Forum the platform repeaters on the SB platform at Northwick Park are flashing. (Wind to just past the 1 minute mark).

Should this not be regarded as a danger signal?

[rincew1nd]

I suspect this is caused by the image capturing; I don't think the signal would actually behave like that.

That said, I have heard a story of a Guard running after his train once waving a green flag; his logic that any item waved violently means stop.

[citysig]

We do not have flashing signal aspects - not on the Met at least.

If a signal was behaving in such a manner, then it would be treated as a signal that is not displaying a clear aspect, could be treated as being a "confusing" aspect and therefore will be classed as a "danger" signal. However, this is a "repeating" signal - the signal to which it is repeating is the one that should be more adhered to.

That said, I'd go with the video capturing giving the "illusion" it is flashing.

[Deleted]

I'll go with MetControl as well. Dot matrix indicators are often difficult to photograph, sometimes not, also 1992 Stock destinations and set numbers, and similarly D Stock destinations.

[Deleted]

It is a strobing effect similar to the way wagon wheels appear to be rotating the wrong way in cowboy films on the TV.

XF

[mrfs42]

Oct 13, 2011 20:17:44 GMT rincew1nd said:

I suspect this is caused by the image capturing; I don't think the signal would actually behave like that.

That said, I have heard a story of a Guard running after his train once waving a green flag; his logic that any item waved violently means stop.

'Stop, stop' - 'Look, I'm telling you to stop'! As the train steamed off up the bank.

No, it wasn't me, but it was my former landlord IIRC...

[metman]

I was at harrow and wealdstone the other week waiting for a NR train to Olympia. There was a four aspect signal on the mainline flashing double yellow. Not seen that before!!

[ducatisti]

Doesn't that mean "You will taking the turning at the next junction"
On that sort of thing, I dimly recall somewhere that flashing green was going to be used on the ECML to mean "turn it up to 11" (140mph running) - did that ever happen?

Back on topic - are all repeaters just repeaters and not distant signals as such (and do distants ever work as anything other than repeaters?)

[rincew1nd]

Green>Flashing Double Yellow>Flashing Yellow>Proceed aspect with feathers.
The proceed aspect could be approach controlled, if the juntion signal is red then the flashing yellows will just be plain yellows.

The flashing green trial on the ECML was a 5th aspect to give higher speed running, AAUI the track work was never done to allow it, though the signalling is still in place.

These kind of flashing signals seen on NR are a much slower deliberate flash, rather than the 'violent' flashing seen in the video.

I *think* repeaters and distants are the same, it just depends on the system. I now get ready to be ripped to shreds by the signalling gurus for my last statement!

[slugabed]

Not an expert but aren't there "fixed distants" always on caution regardless of the aspect of the home (ie not mere repeaters),to ensure that drivers approach with care at all times??
I seem to remember this cropping up in a thread discussing Kew East-jct.

[citysig]

"Distant" signals when showing "Clear", if I remember correctly, inform a driver that all signals within the upcoming control area are clear.

"Repeater" signals generally advise the state of the signal immediately following the repeater. Green repeater = green running signal. Yellow repeater = running signal at danger.

As always there are exceptions to the rule, especially when comparing LU to NR.

[1018509]

As a matter of interest as the signal I was referring to is a platform repeater, and there principally for the guard, (remember them), are these signals ever re-lamped when necessary or are they allowed to go quietly out of commission?

[citysig]

They are kept fully functioning, because aside from being part of the many SPAD mitigation measures, and apart from being used by station staff before giving a train the right, you never know when you may need to use one

[North End]

Oct 14, 2011 12:56:53 GMT 1018509 said:

As a matter of interest as the signal I was referring to is a platform repeater, and there principally for the guard, (remember them), are these signals ever re-lamped when necessary or are they allowed to go quietly out of commission?

During the 1990s some unofficially went out of use at locations where platforms were never staffed. However over the last 10 years or so things have improved and non-functioning platform repeaters are comparatively rare, and tend to get reported and relamped fairly quickly.

Certainly they are regarded as "commissioned equipment" therefore the Infracos or their TFL equivalent are contracted to maintain them in working order.

[Deleted]

What you are seeing is the Duty Cycle (time spent switching on/off) of the LED lamp that is fitted behind the lens. Normally, this is invisible to the naked eye as it happens so fast, but with a continuous frame rate recording, the camera will capture the point at which the lamp is not lit, and appear as if it's flashing.

[norbitonflyer]

Oct 14, 2011 12:55:52 GMT @citysig said:

"Repeater" signals generally advise the state of the signal immediately following the repeater. Green repeater = green running signal. Yellow repeater = running signal at danger.

As always there are exceptions to the rule, especially when comparing LU to NR.

As I understand it, a repeater mimics the action of the main signal - often so that staff other than the driver can see what state the signal is if they can't actually see it (e.g to avoid "ding ding and away" incidents), or for the driver where sighting distances are too short. A distant does not strictly repeat the home signal - it can be put to caution independantly of the home signal it gives warning of - in semaphore territory, it will not clear if a home signal on the same post is at danger.

[citysig]

As I said, a repeater will advise the state of the running signal - they don't necessarily mimic. Signals which do mimic are co-acting signals.

[citysig]

Which of course brings us on to such signals that show green - even if they really "should" be showing red given their trainstop is up - but if they showed red, then trains wouldn't approach them at the speed we want them to approach.

Our drivers drive a world of trickery ;D

[chrisvandenkieboom]

Aren't LU signals designed to show red if the trainstop stays up?

[Dstock7080]

Oct 15, 2011 10:28:45 GMT chrisvandenkieboom said:

Aren't LU signals designed to show red if the trainstop stays up?

Normally a signal trying to clear and the trainstop failing to lower, would result in a dual-aspect.

[21146]

I've noticed the same effect on CCTV looking at South Ken E/B DR platform and seems to appear on signals with LED lamps fitted.

[21146]

I believe there was a 'fixed distant' colour light signal on the approach to Ongar which only ever showed yellow. Ditto the repeater for the home signal at Ealing Broadway (DR) which has only displayed yellow since terminal prorection was brought in, even though there are junction route indicator lights fitted.

[Deleted]

Oct 15, 2011 14:34:48 GMT railtechnician said:

Oct 15, 2011 10:28:45 GMT chrisvandenkieboom said:

Aren't LU signals designed to show red if the trainstop stays up?

Yep but there are trainstops and there are trainstops! Trainstops are not always associated directly with running signals.

I can't actually think of a case where a trainstop would be ON and its associated signal displaying CLEAR unless the air hose had burst and the red light had burnt out.

As one of my old signal supervisors used to say and rightly so "Never forget that green is the danger signal!".

off the top of my head is there one from the vic to the picc at finsbury park which is always up to test tripcocks? or is it just a fixed trainstop?

[trc666]

Isn't that the case for most if not all dead-end platforms that the home signal on the approach to it can only show a red or yellow aspect (with or without route indicator lights)?

RE the Victoria line, I'm not sure about Finsbury Park but there certainly is (or was) a fixed trainstop ramp at Northumberland Park Depot on the southbound track (53 road?) on the approach to the snowcover / tunnel mouths.

[castlebar]

The Great Western regularly used Fixed Distants. Mostly semaphore, but not all, even when semaphores were otherwise common > There was a very brightly lit f.d. southbound, just south of Castlebar Park for years in the '50s and possibly even before that, to protect Drayton Green Junction, which is just around a bend, under a bridge and unsighted. That f.d. could be seen from South Greenford! It was to ensure that a red at Drayton Green didn't catch any driver by surprise after the bend.

[suncloud]

one of my favourite signals is the fixed distant on the approach to st albans abbey.
You can see a similar example here.

[citysig]

Oct 15, 2011 14:34:48 GMT railtechnician said:

I can't actually think of a case where a trainstop would be ON and its associated signal displaying CLEAR unless the air hose had burst and the red light had burnt out.

A900 approaching Baker Street platform 2 northbound.
The signal displays a green to keep trains moving over the junction, but the trainstop stays on until the train is down to (IIRC) 15mph.

[Dstock7080]

Oct 15, 2011 15:44:02 GMT trc666 said:

Isn't that the case for most if not all dead-end platforms that the home signal on the approach to it can only show a red or yellow aspect (with or without route indicator lights)?

The (last) home signal to Ealing Broadway (WP17) shows green when clear.
As 21146 has said, its' repeater always shows yellow.

[Tom]

Oct 15, 2011 18:06:29 GMT @citysig said:

Oct 15, 2011 14:34:48 GMT railtechnician said:

I can't actually think of a case where a trainstop would be ON and its associated signal displaying CLEAR unless the air hose had burst and the red light had burnt out.

A900 approaching Baker Street platform 2 northbound.
The signal displays a green to keep trains moving over the junction, but the trainstop stays on until the train is down to (IIRC) 15mph.

That and VK2 at Finsbury Park are the only two I can think of.

[Tom]

Oct 15, 2011 15:44:02 GMT trc666 said:

Isn't that the case for most if not all dead-end platforms that the home signal on the approach to it can only show a red or yellow aspect (with or without route indicator lights)?

No, that's more Network Rail practice. On LU the last signal prior to a terminal platform is generally red/green, though I think there are exceptions on single lines.