What is real world procedure for a TCF?

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What is real world procedure for a TCF? 24/01/2020 at 05:51 #123008
TylerE
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So, when a TCF occurs in real life, what is actual procedure?

Does the system even detect it as a TCF or is a block just suddenly occupied?

Are trains talked passed the signal? Asked to examine the line?

What if the TCF is in a really "bad" place, like over an LC (forcing it to stay closed)?

Last edited: 24/01/2020 at 05:54 by TylerE
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What is real world procedure for a TCF? 24/01/2020 at 17:16 #123023
TUT
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Quote:
Does the system even detect it as a TCF or is a block just suddenly occupied?
You will see a track circuit section suddenly showing occupied or remaining occupied after the passage of a train.

The instructions are very clear. It is a track circuit showing occupied. It is not to be treated as a track circuit failure until the line has been examined. It could be a train, it could be a broken rail, it could be flooding.

Quote:
Are trains talked passed the signal? Asked to examine the line?
Your first priority is to make sure it's not a train. Make sure that no train has been signalled over the affected portion of line and that the last train over the affected portion has passed clear of the track circuit concerned. Make sure you have seen it occupy and clear the overlap of the signal beyond the affected portion, or else make sure it has passed out of the section complete with tail lamp. If you can see it yourself out of the window, great. Otherwise you may need to stop it and make sure it's complete.

On a single line you must introduce working by pilotman unless there is an exemption in the Signal Box Special Instructions or the line is worked by a token and the driver has it. On a bi-directional line, you must either ensure trains pass in only one direction, or introduce pilot working.

If a train is to pass on an adjacent line before the affected line has been examined, you must caution the driver, tell them you have a track circuit showing occupied, make sure they understand where it is and tell them to pass the affected area at caution and report back as soon as possible if anything is seen to be wrong.

The first train to pass over the affected portion of line will be used to examine the line. Ask the driver if the line appears to be clear as far as they can see. If they confirm it is, you must tell them about the track circuit showing occupied. Make sure they clearly understand the exact location. Make sure you get the whole length of the track circuit examined if necessary. If necessary get the whole signal section examined. Tell the driver to examine the affected portion of line at caution and not to exceed 10 mph through any tunnel on the affected portion. They will have to pass the protecting signal at danger, so you'd go through your who passing a signal at danger routine but you will not call the route over a track circuit showing occupied. Agree a suitable location for the train to report back. While a line is being examined you must caution trains on adjacent lines. Once the examining train has confirmed the line is clear you may treat it as a track circuit failure/track circuit showing occupied when clear (SOWC).

Quote:
What if the TCF is in a really "bad" place, like over an LC (forcing it to stay closed)?
What if it is? You, uh, how can I say this? Suck it up Depending on the severity of things, it may be that train running control and the TOCs start making arrangements to divert certain services, turn services back, it depends. You can use your initiative in certain situations to work trains through the area in the most efficient way to try to minimise delays, but you can't exactly decide unilaterally you're gonna take it upon yourself to divert HSTs via the West of England line, or whatever.

If a track circuit fails over a CCTV level crossing, say, you have to put the barriers in manual raise, arrange for the civil police to be told (because you've essentially just closed a road) and send for a level crossing attendant to place the crossing on local control. Until then, if you have red road-lights working you may allow trains to proceed over the crossing normally on the unaffected line, you can clear the signal. If they're not working (and obviously on the affected line) you'll be passing the protecting signals at danger. That's until the attendant turns up. When the attendant places it on local control, you have to pass signals at danger.

Now there is provision to arrange for a signalling technician to release signalling controls. There are three distinct cases in which you can do this:

Quote:
You may only ask for signalling controls to be released when one of the following applies.

a) A track circuit has failed holding points and it is necessary to move those points to the opposite position.

b) A track circuit or other equipment has failed holding a route and it is necessary to release that route so that signals can be worked or an MA issued for movements that are clear of the failure.

c) An obstruction of the line, derailment or engineering work is keeping a track circuit occupied and it is necessary to work signals or issue an MA for movements that will be clear of the obstruction.

You must not ask for the release of a control which will allow:

- a line clear to be given on any block indicator, or

- a proceed aspect or indication to be displayed by a signal held at danger by a track circuit or axle counter failure

- an MA to be issued beyond an EoA when a track circuit or axle counter failure is preventing it on that route
So if a track circuit is locking points in a really awkward position, it is possible to arrange for a release to move those points. The signalling technician will false clear the track circuit, you can move the points, and then the track circuit will again show occupied. You must not ask for the release of a control which will allow a proceed aspect or indication to be displayed by a signal held at danger by a track circuit or axle counter failure. Also if a track circuit has failed holding a route in, you can release that route to allow trains to be signalled on unaffected lines, to allow you to set routes that are clear of the failure.

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What is real world procedure for a TCF? 24/01/2020 at 18:09 #123024
GeoffM
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TylerE in post 123008 said:
Does the system even detect it as a TCF or is a block just suddenly occupied?
Some systems have track sequence alarms which will alarm if a track is occupied (or unoccupied) out of sequence, or if it "sees" a track become occupied past a red signal (could be a SPAD). It cannot detect all situations though, and is deliberately disabled in limited scenarios such as inside yards (shunting).

SimSig Boss
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What is real world procedure for a TCF? 24/01/2020 at 18:41 #123026
TUT
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GeoffM in post 123024 said:
TylerE in post 123008 said:
Does the system even detect it as a TCF or is a block just suddenly occupied?
Some systems have track sequence alarms which will alarm if a track is occupied (or unoccupied) out of sequence, or if it "sees" a track become occupied past a red signal (could be a SPAD). It cannot detect all situations though, and is deliberately disabled in limited scenarios such as inside yards (shunting).
Good point :)

You still cannot assume it's a TCF, it could still be a broken rail, an obstruction, flooding...

(I know you know that and were just pointing it out, but for the benefit of the OP)

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What is real world procedure for a TCF? 24/01/2020 at 19:51 #123028
Soton_Speed
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TUT in post 123023 said:
If a train is to pass on an adjacent line before the affected line has been examined,...
Is there any general guidance on what constitutes 'an adjacent line' when in a more than two track section or at junctions; or will it be down to local knowledge with reference to common sense and the length of a piece of string?...

In Zone 6, no one can hear you scream...
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What is real world procedure for a TCF? 24/01/2020 at 20:04 #123029
TUT
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Soton_Speed in post 123028 said:
TUT in post 123023 said:
If a train is to pass on an adjacent line before the affected line has been examined,...
Is there any general guidance on what constitutes 'an adjacent line' when in a more than two track section or at junctions; or will it be down to local knowledge with reference to common sense and the length of a piece of string?...
Quote:
20.6.2 First train to pass on an adjacent line

If the first train to pass on a line immediately next to the affected line before the affected line is examined, the driver of this train must be told:

[...]

(Module TS1: General signalling regulations)
Yes, it may take some local knowledge to know whether or not lines which are placed alongside each other on the panel are physically "immediately next to" each other. You could indeed have a single line, or a pair of lines, which are shown on the panel as running parallel the affected line, but which actually head off along quite a different alignment and off onto another branch. Even a single pair of tracks may diverge, for example, between Saunderton and Princes Risborough on the Chiltern lines the Up and Down lines diverge.

The idea behind this regulation is obviously that the problem on the affected line may also be affecting the unaffected line, which isn't going to be a particularly big risk if one line splits off to go through a tunnel, while the other line follows a different course with a less punishing gradient.

If in doubt play safe, but remember the drivers drive up and down day in day out and they could certainly have a discussion with you and come to a clear understanding and they could certainly apply a bit of common sense. It's probably not necessary to go cautiously alongside the up line as it bends off to the right and descends down a gradient

Last edited: 24/01/2020 at 20:06 by TUT
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What is real world procedure for a TCF? 24/01/2020 at 20:06 #123030
clive
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GeoffM in post 123024 said:

Some systems have track sequence alarms which will alarm if a track is occupied (or unoccupied) out of sequence
The Washington DC metro had software that decided whether this was a TC failure and, if so, hid it from the signaller and the Automatic Train Operation system.

One day it wasn't a failure, it was a train.

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What is real world procedure for a TCF? 24/01/2020 at 21:25 #123032
pedroathome
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clive in post 123030 said:
GeoffM in post 123024 said:

Some systems have track sequence alarms which will alarm if a track is occupied (or unoccupied) out of sequence
The Washington DC metro had software that decided whether this was a TC failure and, if so, hid it from the signaller and the Automatic Train Operation system.

One day it wasn't a failure, it was a train.
Now what do I keep being told by a certain member on here, something like, a Track Circuit is to prove the absence of a train, not its presence.

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What is real world procedure for a TCF? 24/01/2020 at 21:46 #123034
VInce
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TUT in post 123029 said:
Soton_Speed in post 123028 said:
TUT in post 123023 said:
If a train is to pass on an adjacent line before the affected line has been examined,...
Is there any general guidance on what constitutes 'an adjacent line' when in a more than two track section or at junctions; or will it be down to local knowledge with reference to common sense and the length of a piece of string?...
Quote:
20.6.2 First train to pass on an adjacent line

If the first train to pass on a line immediately next to the affected line before the affected line is examined, the driver of this train must be told:

[...]

(Module TS1: General signalling regulations)
Yes, it may take some local knowledge to know whether or not lines which are placed alongside each other on the panel are physically "immediately next to" each other. You could indeed have a single line, or a pair of lines, which are shown on the panel as running parallel the affected line, but which actually head off along quite a different alignment and off onto another branch. Even a single pair of tracks may diverge, for example, between Saunderton and Princes Risborough on the Chiltern lines the Up and Down lines diverge.

The idea behind this regulation is obviously that the problem on the affected line may also be affecting the unaffected line, which isn't going to be a particularly big risk if one line splits off to go through a tunnel, while the other line follows a different course with a less punishing gradient.

If in doubt play safe, but remember the drivers drive up and down day in day out and they could certainly have a discussion with you and come to a clear understanding and they could certainly apply a bit of common sense. It's probably not necessary to go cautiously alongside the up line as it bends off to the right and descends down a gradient :P
Just for the record, can someone define "adjacent line" please in the following circumstances

On a four track railway reading say from left to right, up slow, up fast, down fast, down slow where they run the normal distance apart. If there is a track circuit showing occupied on the up slow, for instance would you consider the down fast or slow to be "adjacent lines"?


Its nearly 15 tears since I gave someone a ruling or had a ruling myself so my memory of the detail is fast failing so can anyone refresh my memory of the rules these days for the passage of trains over a track circuit showing occupied in a tunnel. From memory the rule was that it had to be examined at walking pace by a train on the adjacent line before a train on the affected line could pass over it or if no train was available on an adjacent line, examined by someone on foot walking through the tunnel. Is that still the case?

Vince

Last edited: 24/01/2020 at 22:05 by VInce
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What is real world procedure for a TCF? 24/01/2020 at 22:30 #123035
TUT
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VInce in post 123034 said:
Just for the record, can someone define "adjacent line" please in the following circumstances

On a four track railway reading say from left to right, up slow, up fast, down fast, down slow where they run the normal distance apart. If there is a track circuit showing occupied on the up slow, for instance would you consider the down fast or slow to be "adjacent lines"?
I wouldn't have thought you would consider either of them to be adjacent lines, but you know how it goes, it's like, well now you're asking ...

The Rule Book clearly says "immediately next to", so I wouldn't have thought it would be necessary.

VInce in post 123034 said:
Its nearly 15 tears since I gave someone a ruling or had a ruling myself so my memory of the detail is fast failing so can anyone refresh my memory of the rules these days for the passage of trains over a track circuit showing occupied in a tunnel. From memory the rule was that it had to be examined at walking pace by a train on the adjacent line before a train on the affected line could pass over it or if no train was available on an adjacent line, examined by someone on foot walking through the tunnel. Is that still the case?
That requirement is no longer in force. The only restrictions are that the train must not exceed 10 mph through a tunnel if examining the line in the tunnel, you cannot allow a train with a failed headlight to examine the line in a tunnel unless a portable headlight has been fitted, and you must not allow another train to enter or pass through a tunnel while a train is being used to examine the line within the tunnel.

The Rule Book doesn't seem to make any explicit exception for tunnels with separate bores, but you would imagine ...

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What is real world procedure for a TCF? 25/01/2020 at 13:36 #123046
Giantray
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Track Circuits also come in the form of Axle-Counters, which has a similar process to dealing with a failure, but they can be reset.

Failure of a track circuit will nearly alway require flagging past a red signal. However some newly re-signalled areas have POSA signals that allow the Signaller to signal a train over a failed track circuit with the interlocking intact, no requirement to use Route Cards, but the first train must be spoken to, to examine the line. After that trains can be POSA signalled without talking to the drivers.

As regards track circuit locking points, there is in new signalling areas a process called TREL and PREL. Two separate procedures that under strict regulations allow a Signaller to release a failed track circuit to be able to release a route locked by the errant track circuit, or to move a set of points to another position.

Professional Railwayman since 1981. Railway Historian (SER, LCDR)
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