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Saltley 294 - Approach Locking Bug?

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Saltley 294 - Approach Locking Bug? 13/01/2013 at 18:26 #40527
Danny252
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1461 posts
Signal 294 is on the Down Slow at Coleshill/Hams Hall, and as a semi-auto signal, normally (i.e. no ACOA risk) you can drop it without approach locking coming into effect, to allow a train out of Hams Hall or Coleshill Down Sdgs.

However, in the attached save, it's convinced it needs 120 seconds to drop - but there's no train at it or the signal in rear (296), and no route is set to 296 so nothing further back is being affected. Resetting and cancelling the route begins the approach locking again, whether or not the auto button is set.

I remember there being a semi-auto on Trent around Ratcliffe that always did this due to a bug, but the fact this is normally works is odd, and I'm not sure quite what the cause of it is - plenty of people must have cancelled the route without issue, so it seems to be something very specific!

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Saltley 294 - Approach Locking Bug? 14/01/2013 at 00:22 #40535
Stephen Fulcher
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2025 posts
SY294 is a controlled signal and not semi-automatic.

If you set and cancel the same route on a "blank" sim with not trains about there is no timeout applied, and in your save there are no approaching trains for miles.

I am unsure of whether or not there is any intentional locking with either T663 or the route from S289 upon which 6D37 is approaching, but once S294 times out completely and sets again it does not time out if cancelled, which suggests a possible interaction with 6D37 of some kind as it moves along.

I then tried cancelling the route on S289 (causing an ACOA to 6D37) and then resetting and cancelling the route from S294 whilst S289 was still timing out and there was no timeout for S294.

My theory therefore is that a bug exists.

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Saltley 294 - Approach Locking Bug? 14/01/2013 at 00:26 #40536
Danny252
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1461 posts
" said:
SY294 is a controlled signal and not semi-automatic
Ah bugger, I never quite the distinction right. I'll go look it up, again - though I think the actual definition has varied a few times (or by region or something).

Last edited: 14/01/2013 at 00:27 by Danny252
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Saltley 294 - Approach Locking Bug? 14/01/2013 at 04:41 #40538
GeoffM
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6282 posts
I've had a quick look at the sim data and it looks like latched approach locking is used throughout the sim. Most relay interlockings, of which this is in the periods simulated, have a relay that latches when a train hits the strike-in point - in this case when approaching Whitacre Jn. If the train doesn't pass the signal but instead moves away - for example, into the Whitacre Goods Loop, reversing at SY513 - then the signal will still time out if the route is cancelled.

SSI/Westlock/Smartlock instead do the look-back for trains approaching at the time of pulling the route so it doesn't suffer this issue.

Mind you, all the above assume comprehensive approach locking has been provided. In the days of relays that was expensive so many interlockings timed out no matter what. Quite a few SSI/WL/SL areas with either some or all signals without comprehensive approach locking too.

SimSig Boss
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Saltley 294 - Approach Locking Bug? 14/01/2013 at 13:26 #40554
Danny252
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1461 posts
" said:
I've had a quick look at the sim data and it looks like latched approach locking is used throughout the sim. Most relay interlockings, of which this is in the periods simulated, have a relay that latches when a train hits the strike-in point - in this case when approaching Whitacre Jn. If the train doesn't pass the signal but instead moves away - for example, into the Whitacre Goods Loop, reversing at SY513 - then the signal will still time out if the route is cancelled.

SSI/Westlock/Smartlock instead do the look-back for trains approaching at the time of pulling the route so it doesn't suffer this issue.

Mind you, all the above assume comprehensive approach locking has been provided. In the days of relays that was expensive so many interlockings timed out no matter what. Quite a few SSI/WL/SL areas with either some or all signals without comprehensive approach locking too.
Interesting - I have feeling I might have had a train pull up to 304 and yell loudly at me on the phone that he'd actually like to go into Hams Hall, rather than dare take his train closer to B'ham, which would've triggered the strike-in before I reset the route. However, pulling 289 resulting in resetting the timer on 296, as Stephen says, is an odd one.

Last edited: 14/01/2013 at 13:26 by Danny252
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Saltley 294 - Approach Locking Bug? 14/01/2013 at 17:43 #40564
GeoffM
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6282 posts
" said:
Interesting - I have feeling I might have had a train pull up to 304 and yell loudly at me on the phone that he'd actually like to go into Hams Hall, rather than dare take his train closer to B'ham, which would've triggered the strike-in before I reset the route. However, pulling 289 resulting in resetting the timer on 296, as Stephen says, is an odd one.
I can't get my head around that one! I'll have another look later when I'm more awake.

SimSig Boss
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Saltley 294 - Approach Locking Bug? 14/01/2013 at 19:42 #40571
Danny252
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I should probably have been more awake when writing it!

Boils down to "I think I cancelled a route for a train after it struck in to the Approach Locking 'area', which explains why it's going off. But why does cancelling the route from 289 remove the Approach Locking timer, as in Stephen's post?"

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