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Clearing Point Violation

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Clearing Point Violation 05/05/2019 at 19:19 #118112
Ford
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Can someone explain what this is, and how I might avoid it? I have vaguely established that setting the points before setting the route at Hilton Jnc prevents this from occuring when I send a train to Ladybank - but I'm yet to workout how to avoid getting this when setting a route into the Montrose sidings - even when there's not a train in sight in either direction, I get a 'clearing point violation' - can someone explain? I've not been able to find anything in the manual or forums that really explains this.

Thanks

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Clearing Point Violation 05/05/2019 at 19:25 #118114
Hap
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Have a wee look at this https://www.simsig.co.uk/Media/Wiki/%2Fusertrack%2Fmans%2Fnescot%2Fnescot-clearing-points.pdf

Have you got the points set into Montrose number 1 siding before any train has came to a stand at signal MS15?

Points MS11 must remain in the normal position until the train has came to a stand at signal MS15. Give that a try and see what happens.

Craig (HAP)

HAP
Last edited: 05/05/2019 at 19:57 by Hap
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Clearing Point Violation 05/05/2019 at 19:48 #118115
Steamer
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Ford in post 118112 said:
Can someone explain what this is, and how I might avoid it? I have vaguely established that setting the points before setting the route at Hilton Jnc prevents this from occuring when I send a train to Ladybank - but I'm yet to workout how to avoid getting this when setting a route into the Montrose sidings - even when there's not a train in sight in either direction, I get a 'clearing point violation' - can someone explain? I've not been able to find anything in the manual or forums that really explains this.

Thanks
At Montrose, you need to wait for an approaching train to come to a stand at the relevant signal before setting the route into the sidings.

On other simulations, you may have come across locations where you have to wait for an overlap to time out before setting a route into sidings- the principle is the same (indeed, clearing points are the Absolute Block equivalent of overlaps).

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Clearing Point Violation 05/05/2019 at 22:11 #118117
jrr
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An example: Trains terminating at Bedwyn on Westbury cannot be signalled into the siding until the overlap has timed out after the train arrives at Bedwyn.
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Clearing Point Violation 06/05/2019 at 00:29 #118118
TUT
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So in absolute block world the line is divided into sections, with a signal box at the start (signal box A) and a signal box at the end (signal box B). Signal box B will of course be at the start of the next section to signal box C and so on.

The section is the line between the last stop signal controlled from one signal box, and the home signal (the first stop signal) controlled by the next signal box.

In absolute block, signaller A offers the train to signal box B, by sending the appropriate is line clear?

Before signaller B can accept the train, they must make sure the line is clear up to and including the clearing point -- which is defined as the point up to which the line must be clear before a train can be accepted. If the distant signal is a colour light signal, the clearing point is usually 183m (200yd) beyond the home signal. If the distant is a semaphore, the clearing point is extended to a point usually 400m (440yd) beyond the home signal. They must also ensure that all points within the clearing point have been set for the safety of the approaching train, that no conflicting movement has been authorised that will cross or foul the line within the clearing point and that no train has been accepted from another direction that requires a portion of the same line within the clearing point for acceptance,

Once signaller B has accepted that train by acknowledging is line clear they cannot allow the line to be obstructed within the clearing point for that train until the train has been stopped at the home signal or has passed beyond any points or crossings that signaller B wishes to use within the clearing point. This applies unless signaller A sends cancelling (3-5) or the train has failed.

So

Before you the simsig player send a train from one signal box to the next you have to make sure that the line is clear up to and including the clearing point (183m or 400m beyond the next signal, depending - exact locations can be found in the link hap posted) and that all the points within the clearing point are set for the safety of the train (so make sure a proper route is set all the way for a train, with no trailing points incorrectly set) and that you haven't signalled a train from another direction which also requires a part of the same line to be clear.

And then you cannot obstruct the clearing point and you must maintain a complete 183m/400m portion of line with all points within it correctly set until the train comes to a stand at the next signal. At Montrose, if you set the route into the sidings, you've destroyed the clearing point for the train.

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Clearing Point Violation 06/05/2019 at 19:05 #118129
kbarber
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TUT in post 118118 said:
So in absolute block world the line is divided into sections, with a signal box at the start (signal box A) and a signal box at the end (signal box B). Signal box B will of course be at the start of the next section to signal box C and so on.

The section is the line between the last stop signal controlled from one signal box, and the home signal (the first stop signal) controlled by the next signal box.

In absolute block, signaller A offers the train to signal box B, by sending the appropriate is line clear?

Before signaller B can accept the train, they must make sure the line is clear up to and including the clearing point -- which is defined as the point up to which the line must be clear before a train can be accepted. If the distant signal is a colour light signal, the clearing point is usually 183m (200yd) beyond the home signal. If the distant is a semaphore, the clearing point is extended to a point usually 400m (440yd) beyond the home signal. They must also ensure that all points within the clearing point have been set for the safety of the approaching train, that no conflicting movement has been authorised that will cross or foul the line within the clearing point and that no train has been accepted from another direction that requires a portion of the same line within the clearing point for acceptance,

Once signaller B has accepted that train by acknowledging is line clear they cannot allow the line to be obstructed within the clearing point for that train until the train has been stopped at the home signal or has passed beyond any points or crossings that signaller B wishes to use within the clearing point. This applies unless signaller A sends cancelling (3-5) or the train has failed.

So

Before you the simsig player send a train from one signal box to the next you have to make sure that the line is clear up to and including the clearing point (183m or 400m beyond the next signal, depending - exact locations can be found in the link hap posted) and that all the points within the clearing point are set for the safety of the train (so make sure a proper route is set all the way for a train, with no trailing points incorrectly set) and that you haven't signalled a train from another direction which also requires a part of the same line to be clear.

And then you cannot obstruct the clearing point and you must maintain a complete 183m/400m portion of line with all points within it correctly set until the train comes to a stand at the next signal. At Montrose, if you set the route into the sidings, you've destroyed the clearing point for the train.
An excellent explanation, and may well reflect current practice. But back in the day the different companies (and their successor regions) varied in whether they allowed clearing points to be changed after accepting a train and before it came to a stand. The GWR was very strict in that regard; once you accepted something you were locked up until it stopped or passed, unless there was a specific exception in the Signal Box Special Instructions (AKA 'footnotes'). I have a feeling that way of working tended to be used where 4-track lines were paired by direction (such as the GNR), and certainly I've heard of an inspector who was ex-GN challenging a Midland line signalman who swung a junction with a train on the block (in fact, at Finchley Road, the train was almost certainly in the section). It would make sense that where lines are paired by use (such as the Midland or the LNWR), it would be considered aceptable to swing the clearing point - provided the new clearing point was properly unobstructed etc. There was even a provision in the General Appendix, of all places, that if points were to be swung ahead of an approaching train, the signalman must satisfy himself that it was safe to do so, having regard to the position and speed of the approaching train.

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Clearing Point Violation 12/05/2019 at 00:05 #118225
Ford
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TUT in post 118118 said:

And then you cannot obstruct the clearing point and you must maintain a complete 183m/400m portion of line with all points within it correctly set until the train comes to a stand at the next signal. At Montrose, if you set the route into the sidings, you've destroyed the clearing point for the train.
Thankyou - that's very clear, (I think!) - so - is it even possible to route a train through to Montrose head-shut siding without causing this 'error'? I've ensured that the track is all clear in both directions, that that the points are set into the sidings and waited for the train to come to a halt at MS15 before setting the route, and the train proceeds, but as soon as it leaves the track section directly behind MS15, I get a violation penalty.

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Clearing Point Violation 12/05/2019 at 10:44 #118227
TUT
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Ford in post 118225 said:
TUT in post 118118 said:

And then you cannot obstruct the clearing point and you must maintain a complete 183m/400m portion of line with all points within it correctly set until the train comes to a stand at the next signal. At Montrose, if you set the route into the sidings, you've destroyed the clearing point for the train.
Thankyou - that's very clear, (I think!) - so - is it even possible to route a train through to Montrose head-shut siding without causing this 'error'? I've ensured that the track is all clear in both directions, that that the points are set into the sidings and waited for the train to come to a halt at MS15 before setting the route, and the train proceeds, but as soon as it leaves the track section directly behind MS15, I get a violation penalty.
You're welcome :)

I thought you might be interested in what a clearing point is in general and what a 'clearing point violation' is supposed to mean.

As to the specific situation at Montrose, if you have a look at the diagram hap linked to, you can see that there is only one possible clearing point and that's with the points leading to the sidings (MS11) normal. In other words you cannot have the points set for the siding when you signal the train up to MS15. You have to wait for the train to come to a stand at MS15 before setting the route into the siding (including moving the points). That should then work.

It's typical for clearing points not to include sidings, so you have to accept a train with the points set away from the sidings and then move the points and clear the signal only when the train is at a stand. I've never done an AB course, so I don't know exactly where that's covered in the rule book, whether the phrase "all points within the clearing point have been set for the safety of the approaching train" covers that or whether it's down to signal box special instructions to define acceptable clearing points for a given box I'm not really sure, I just wanted to give you a bit of background.

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Clearing Point Violation 12/05/2019 at 10:47 #118228
TUT
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kbarber in post 118129 said:
An excellent explanation, and may well reflect current practice. But back in the day the different companies (and their successor regions) varied in whether they allowed clearing points to be changed after accepting a train and before it came to a stand. The GWR was very strict in that regard; once you accepted something you were locked up until it stopped or passed, unless there was a specific exception in the Signal Box Special Instructions (AKA 'footnotes'). I have a feeling that way of working tended to be used where 4-track lines were paired by direction (such as the GNR), and certainly I've heard of an inspector who was ex-GN challenging a Midland line signalman who swung a junction with a train on the block (in fact, at Finchley Road, the train was almost certainly in the section). It would make sense that where lines are paired by use (such as the Midland or the LNWR), it would be considered aceptable to swing the clearing point - provided the new clearing point was properly unobstructed etc. There was even a provision in the General Appendix, of all places, that if points were to be swung ahead of an approaching train, the signalman must satisfy himself that it was safe to do so, having regard to the position and speed of the approaching train.
Really interesting, thank you!

I looked through the rule book, but to be honest, I couldn't find anything explicit about changing the clearing points. It probably is still down to local instructions I would have thought? The rule book doesn't seem (as far as I could find) to explicitly address changing the clearing point from one acceptable clearing point to another acceptable clearing point. But, whatever the weather, a clearing point must be maintained, whether or not it's the same one throughout. And at Montrose, for example, the points can't be set into the sidings when the train is accepted or on the line.

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Clearing Point Violation 12/05/2019 at 11:37 #118229
postal
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TUT in post 118227 said:
In other words you cannot have the points set for the siding when you signal the train up to MS15. You have to wait for the train to come to a stand at MS15 before setting the route into the siding (including moving the points). That should then work.
My understanding of AB working is sketchy to say the least but unfortunately, in the testing I've done, I don't think it is working correctly. Sim is set up with none of the options checked (mechanical interlocking, Montrose resignalling etc). Halt a train at MS15, set the route forward to MS37 and as soon as the train is fully past MS15 and clears TC TMS4479 a clearing point violation message is generated.

Reported on Mantis #24975 (in the hope that my sketchy understanding has actually identified a bug).

"If you can find something everyone agrees on, it's wrong." - Morris King Udall (15/06/1922 – 12/12/1998), American politician.
Last edited: 12/05/2019 at 11:38 by postal
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Clearing Point Violation 12/05/2019 at 21:30 #118244
Ford
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TUT in post 118227 said:

...In other words you cannot have the points set for the siding when you signal the train up to MS15. You have to wait for the train to come to a stand at MS15 before setting the route into the siding (including moving the points). That should then work.
Ah - then something is definitely up - my train is stopped at MS15. The violation only happens after I've set the points and the train has passed MS15 into the siding.

Thanks for the background - very enlightening!

Dave

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Clearing Point Violation 12/05/2019 at 22:25 #118247
TUT
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Ford in post 118244 said:
TUT in post 118227 said:

...In other words you cannot have the points set for the siding when you signal the train up to MS15. You have to wait for the train to come to a stand at MS15 before setting the route into the siding (including moving the points). That should then work.
Ah - then something is definitely up - my train is stopped at MS15. The violation only happens after I've set the points and the train has passed MS15 into the siding.

Thanks for the background - very enlightening!

Dave
You're most welcome :)

Sorry for assuming you were doing the wrong thing and not bothering to load up the sim myself and check!

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Clearing Point Violation 13/05/2019 at 10:16 #118255
kbarber
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TUT in post 118228 said:
kbarber in post 118129 said:
An excellent explanation, and may well reflect current practice. But back in the day the different companies (and their successor regions) varied in whether they allowed clearing points to be changed after accepting a train and before it came to a stand. The GWR was very strict in that regard; once you accepted something you were locked up until it stopped or passed, unless there was a specific exception in the Signal Box Special Instructions (AKA 'footnotes'). I have a feeling that way of working tended to be used where 4-track lines were paired by direction (such as the GNR), and certainly I've heard of an inspector who was ex-GN challenging a Midland line signalman who swung a junction with a train on the block (in fact, at Finchley Road, the train was almost certainly in the section). It would make sense that where lines are paired by use (such as the Midland or the LNWR), it would be considered aceptable to swing the clearing point - provided the new clearing point was properly unobstructed etc. There was even a provision in the General Appendix, of all places, that if points were to be swung ahead of an approaching train, the signalman must satisfy himself that it was safe to do so, having regard to the position and speed of the approaching train.
Really interesting, thank you!

I looked through the rule book, but to be honest, I couldn't find anything explicit about changing the clearing points. It probably is still down to local instructions I would have thought? The rule book doesn't seem (as far as I could find) to explicitly address changing the clearing point from one acceptable clearing point to another acceptable clearing point. But, whatever the weather, a clearing point must be maintained, whether or not it's the same one throughout. And at Montrose, for example, the points can't be set into the sidings when the train is accepted or on the line.
I don't think this sort of detail ever appeared in the Rule Book or in SBSIs. It was down to enforcement of local practice (which, to a degree, emerged from interpretation by the operations management of the railway concerned). So Western lines always required the clearing point to be maintained unchanged (unless specifically authorised in the footnotes) until a train had passed, stopped or been cancelled off; that was how Regulation 4 was interpreted and the interpretation was enforced by the District Inspectors, without any need for published instructions. Of course, given the existence of the GA instruction, Reg 4 could equally be interpreted as meaning you could swing the clearing point; again, such a practice would emerge out of practical necessity and become normal practice as a result of DIs raising no objection when it was done.

For example, at Finchley Road (on the Midland line, just north of Belsize Tunnel), swinging the clearing point was pretty much essential to keep the traffic moving. In the old layout (pre West Hampstead PSB), the Fast and Local lines converged to run through what is now the slow line bore (the goods lines used what is now the fast line bore). It was common (several times an hour in the peak) to have a down train offered - often, indeed, in section - from Carlton Road Junction, that needed to run to the local line (nowadays renamed the slow). Meanwhile, an express would be approaching up the fast, and would of course get proceedings at the junction, althpough the signalman would offer the down road to West Hampstead so there was 'Line Clear' on the block ready. By the time the express passed, the headlights of the down road would usually be visible in the tunnel; at that point the junction would be swung (4 levers - switch diamonds and FPLs as well as the facing points) and the signals cleared. To have stopped the down road at the signal before swinging the junction (plus the time taken for it to start away, on quite a steep gradient) would almost certainly have meant delays to the following train (often a down express).

Of course, with a mechanical frame, those levers could be got across at least as quickly as point machines could have driven the junction over.

But you're absolutely right: subject to the brief period of swinging it, where such is permitted, a clearing point must be maintained until the train has come to a stand, passed or been cancelled off the block. In some cases - and provided it's long enough - a siding will provide an acceptable clearing point (we had that option for up road moves at Kensington South Main, using Warwick Road Sidings - the points into the sidings could be locked both ways, which was probably the key). Again, this sort of thing is rarely set out int he SBSIs, it's a matter of local knowledge - at Junction Road https://signalbox.org/diagrams.php?id=706 it was possible to lock 19 points into the down reception both ways, but not permitted to use it for a clearing point - presumably because it was worked 'No block' (effectively a siding) and Upper Holloway could have backed something in that would have infringed the clearing point.

Last edited: 13/05/2019 at 10:29 by kbarber
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