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train crash without user interaction #3928

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DorpsGek opened this issue Jul 5, 2010 · 4 comments
Closed

train crash without user interaction #3928

DorpsGek opened this issue Jul 5, 2010 · 4 comments
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flyspray This issue is imported from FlySpray (https://bugs.openttd.org/)

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@DorpsGek
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DorpsGek commented Jul 5, 2010

TomyLobo opened the ticket and wrote:

The situation:
both trains are stopped, one of them is in the left depot.

Steps for causing the bug:

  1. load the savegame
  2. start the left train and stop it just beyond the center of the signal tile
  3. start the right train. It will pass the first signal and halt at the middle signal.
  4. start the left train (might not be that visible in the depot), it will crash into the right train

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Reported version: 1.0.2
Operating system: Windows


This issue was imported from FlySpray: https://bugs.openttd.org/task/3928
@DorpsGek
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DorpsGek commented Jul 5, 2010

TomyLobo wrote:

attached a screenshot

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This comment was imported from FlySpray: https://bugs.openttd.org/task/3928#comment8253

@DorpsGek
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DorpsGek commented Jul 5, 2010

Vitus wrote:

Also happens in trunk.

edit: This crash only happens when the left train reserves path but doesn't enter the signal block yet (i.e. left train reserves path up to the twoway signal (as it should), but the right train disregards it as long as the left one is outside of the signal block)

edit2: Attached smaller and simplier savegame; just start train 2.
edit3: Also happens without the middle PBS.

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This comment was imported from FlySpray: https://bugs.openttd.org/task/3928#comment8254

@DorpsGek
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DorpsGek commented Jul 9, 2010

michi_cc wrote:

This is basically intended behavior. The "train in signal block" state is not propagated through path signals
for performance reasons. There is a failsafe that a train entering a PBS block through a block signal tries
to reserve a path as soon as it crosses the signal, but this fails when the block signal in question is a two-
sided block signal that is already the destination of another train. This is something not really fixable.


This comment was imported from FlySpray: https://bugs.openttd.org/task/3928#comment8282

@DorpsGek
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Rubidium closed the ticket.

Reason for closing: Won't fix

When a train has reserved a path from a path signal to a two way block signal and the reservation passes a path signal through the back another train can enter the reserved path (only) via that same two way block signal.
The reason for this has to do with optimisation; to fix this issue the signal update has to pass all path signals until it finds either a train or a backwards facing signal. This is a very expensive task.
The (signal) setups that allow these crashes can furthermore be considered incorrectly signalled; one extra safe waiting point for the train entering from path signal just after the backwards facing signal (from the path signal train) resolves the issue.


This comment was imported from FlySpray: https://bugs.openttd.org/task/3928

@DorpsGek DorpsGek added flyspray This issue is imported from FlySpray (https://bugs.openttd.org/) bug labels Apr 7, 2018
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