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5W74 over-written by 5R10

You are here: Home > Forum > Simulations > Released > Central Scotland > 5W74 over-written by 5R10

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5W74 over-written by 5R10 14/09/2021 at 12:45 #141555
bugsy
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I’ve just had two trains leave Eastfield TMD in quick succession, both heading for Queen Street. 5W74 is bound for P7 and 5R10 is bound for P4.
When 5R10 reaches Cowlairs West Junction its TD leaps forward and over-writes that of 5W74 which is at Cowlairs South Junction. (see screenshot)
None of this is a problem as I can just insert the TDs and carry on (hopefully).

I reloaded the most recent save and it happened again. Save attached.
...


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5W74 over-written by 5R10 14/09/2021 at 18:00 #141562
y10g9
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Had you routed CC531 (shunt signal at the end of the DPL) towards CQ53 before 5W74 had passed CQ53? CC531 appear to be permissive and has an approach release that will mean after a certain length of time that the TC before it is occupied for, it will then clear even thought the signal section ahead is occupied.
I ran your save, and routed 5R10 out relatively shortly after it appeared. 5R10 passed CC531 before 5W74 had passed CQ53. This causes the sim to correctly step the TD from CC531 to CQ53 which overwrites the TD that is already there. 8 Seconds later 5W74 passed CQ53 which causes the TD at CQ53 to step forwards to the next berth. There is no leaping forward of 5R10 TD, just a case of it stepped from CC531 to CQ53, then very quickly was stepped on to the next signal

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5W74 over-written by 5R10 14/09/2021 at 19:46 #141563
bugsy
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So should I have held 5R10 back?
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5W74 over-written by 5R10 14/09/2021 at 20:04 #141564
Albert
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Yes, but in the absence of documentation, you couldn't have known that the signal behaved this way. Many other shunt signals on SimSig are either not permissive (showing red if the track ahead is occupied) or give an error if there is an onward route set for the other train.
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5W74 over-written by 5R10 14/09/2021 at 20:19 #141565
Peter Bennet
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y10g9 in post 141562 said:
Had you routed CC531 (shunt signal at the end of the DPL) towards CQ53 before 5W74 had passed CQ53? CC531 appear to be permissive and has an approach release that will mean after a certain length of time that the TC before it is occupied for, it will then clear even thought the signal section ahead is occupied.
I ran your save, and routed 5R10 out relatively shortly after it appeared. 5R10 passed CC531 before 5W74 had passed CQ53. This causes the sim to correctly step the TD from CC531 to CQ53 which overwrites the TD that is already there. 8 Seconds later 5W74 passed CQ53 which causes the TD at CQ53 to step forwards to the next berth. There is no leaping forward of 5R10 TD, just a case of it stepped from CC531 to CQ53, then very quickly was stepped on to the next signal
That's my conclusion too, there are probably additional conditions involved that I'd need the control tables for.

Peter

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5W74 over-written by 5R10 14/09/2021 at 20:31 #141566
y10g9
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Albert in post 141564 said:
Many other shunt signals on SimSig are either not permissive (showing red if the track ahead is occupied) or give an error if there is an onward route set for the other train.
The error you're talking about (Route set from the exit signal - call-on not allowed) only applies to main signals with a call-on facility, not to shunt signals. Shunt signals don't have the same restrictions as main aspect. There are plenty of other examples where a shunt will clear to an occupied TC with the main aspect off.

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5W74 over-written by 5R10 14/09/2021 at 20:47 #141567
Albert
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Thanks - you're entirely right - I remember having seen similar situations on other sims but wasn't sure how common it was.

In this case the front train's TD is lost because the track doesn't have a second berth. Even if it had a second berth (and the sim were coded to step the 2nd TD into the rear berth - not all sims are, reflecting reality), I guess the movement would still be not allowed.

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5W74 over-written by 5R10 14/09/2021 at 23:34 #141568
Phil-jmw
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It is considered to be bad practice to 'overset' from a shunt signal in a sidings to a signal on a main line with a train in the section in between for this very reason, as it is easy to wind up with two in a section.
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5W74 over-written by 5R10 15/09/2021 at 18:30 #141579
VInce
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Last edited: 15/09/2021 at 20:13 by VInce
Reason: None given

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