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Choose signals incorrectly allowing trains to enter occupied platforms

Started by freddyhayward, September 16, 2020, 06:36:39 AM

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freddyhayward

No reproduction case yet. This issue has been noticed by myself and VOLVO on bridgewater-brunel. It usually leads to line or network-wide jams.

VOLVO

Can confirm the case and it seems to be happening more and more frequently, now it really doesn't take long at all for it to happen. However the issue seems to happen only on station size with 2 to 3 deadend platforms with mechanical choose signal, namely on the North Eastern Railway network of bridgewater-brunel, only on Connell, Pitthorne and Nellingchester. It never happens on Bargate where there are only 2 platforms but vane choose signals are adopted. It also never happens on Great Peningpike where there are 3 platforms, but is a through station.

freddyhayward

Quote from: VOLVO on September 16, 2020, 07:15:14 AM
Can confirm the case and it seems to be happening more and more frequently, now it really doesn't take long at all for it to happen. However the issue seems to happen only on station size with 2 to 3 deadend platforms with mechanical choose signal, namely on the North Eastern Railway network of bridgewater-brunel, only on Connell, Pitthorne and Nellingchester. It never happen on Bargate where there are only 2 platforms but vane choose signals are adopted.
On my network, it happened at Arlsing and the Port of Fleckwater which each had 4 dead-end platforms.

VOLVO

After some more observation on stations with choose signals, i have discovered in the through station Taning Boundary Street, where circular metro trains are set to wait for schedule, other circular metro trains will select empty platforms correctly. Where as trains from another route which are not set to wait at the station will not choose correctly, but enter and wait at platforms occupied by the circular metro trains.

freddyhayward

Quote from: VOLVO on September 16, 2020, 07:21:25 AM
After some more observation on stations with choose signals, i have discovered in the through station Taning Boundary Street, where circular metro trains are set to wait for schedule, other circular metro trains will select empty platforms correctly. Where as trains from another route which are not set to wait at the station will not choose correctly, but enter and wait at platforms occupied by the circular metro trains.
This was true for both of my cases too. They were both goods trains that were not set to wait there.

jamespetts

Thank you all for the report. I am afraid that it will not be possible for me to investigate this without a reproduction case.
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VOLVO

After some offline testing it would seem that whenever a train is scheduled to stop but not wait at a station, the choose signal will fail to direct the train to an empty platform, however, if a train is scheduled to not stop or wait at a station, the problem does not occur. Until when the choose signal decided to not be a choose signal again and direct a train to an occupied platform again.

Sirius

Could you please create a small savegame where this exact behavior will happen after a short time?
That will finally allow James to look into this I guess.

VOLVO

Quote from: Freahk on September 21, 2020, 12:16:52 PM
Could you please create a small savegame where this exact behavior will happen after a short time?
That will finally allow James to look into this I guess.
I have tested it on the bridgewater-brunel game after a disync, I will try to create a stand alone test map tonight if I have time.

freddyhayward

Here's an image showing problem. A common thread seems to be between one convoy departing after having waited for its timetable, and another entering in drive-by-sight and not scheduled to wait for a time.

jamespetts

Thank you for that. As indicated, however, there is little that I can do without a reliable means of reproducing this.
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Sirius

Hopefully it is related to the desynching, so we might catch it that way.
It seems to happen only on busy saves.
I was multiple times attempting to create a small save with this issue without any success and I guess I am not the only one who tried.
So might be some kind of race condition caused by a missing mutex or something like that, though that's pure guessing.

freddyhayward

Quote from: jamespetts on October 10, 2020, 09:47:40 AM
Thank you for that. As indicated, however, there is little that I can do without a reliable means of reproducing this.
I understand, but my hope is that compiling enough information will increase the chance of discovering a reproduction case.

jamespetts

Quote from: freddyhayward on October 10, 2020, 10:35:48 AM
I understand, but my hope is that compiling enough information will increase the chance of discovering a reproduction case.

Excellent, thank you.
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freddyhayward

Another occurrence for the record. All convoys heading the wrong direction seem to be in drive-by-sight. Is there any reason why a choose signal should ever allow trains to pass at drive-by-sight?

jamespetts

Quote from: freddyhayward on October 17, 2020, 10:27:16 PM
Another occurrence for the record. All convoys heading the wrong direction seem to be in drive-by-sight. Is there any reason why a choose signal should ever allow trains to pass at drive-by-sight?


Not unless they are permissive, but I doubt that any are in fact encoded as such.
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Sirius

Encoding a signal as permissive choose does not make any sense anyways.

freddyhayward