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Author Topic: Token block signals not clearing previous block  (Read 418 times)

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Offline Matthew

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Token block signals not clearing previous block
« on: June 08, 2018, 09:34:32 AM »
There's an unexpected pattern with token block signalling, which seems to be different from the other bug reports.

Steps to reproduce:
1. Open the savegame provided and pause immediately.
2. Turn on signalling view (Shift-B) and examine tile (791, 712). The file should open here, but if it somehow opens in the wrong place or rotation, this is in a block on the railway between Wake Perborough and Panton, in the very large loop, in the direction of Panton.
3. Note that the tile is still reserved by convoy 376, which has now passed not only the token block signal at (790, 711), but also several more signals beyond that, and therefore should have cleared the section covering (791, 712). This is preventing convoy 390 from passing the absolute block signal (792, 714).
4. Open the window for convoy 390.
5. Now go to (769,640) and note the location of convoy 376.
6. Unpause. As convoy 376 clears the next token block signal on its route (769, 640), it finally clears the earlier reservation and convoy 390 is able to move again. But 376 has now failed to fully clear the block behind (769, 640).

This pattern has occurred in multiple locations in this game, and the common factor is that it's always behind a token block signal. The reason why this particular tile is still reserved seems to be that it was at the rear of convoy 376 when the token block signal changed to 'clear'.

You can see that there is a one-way sign at (791,712), but after much deleting and moving of one-way signs, I think that's probably (but not certainly) a coincidence. It might be relevant that the signal is on a 'diagonal' line; this unexpected behaviour does not occur at (706, 591), where the railway aligns with the grid. But it does seem to occur at other aligned tiles.

The fact that the signal leaves behind a bit of mess that needs to be cleared up is somehow symbolic for your wider struggle with the signalling code, James.  :P In Chinese, we say 'add fuel!' to cheer someone on. I hope that someday you can put a bit more coke in your firebox and build up steam to have a look at this.  :)
« Last Edit: June 08, 2018, 10:02:38 AM by Matthew »

Offline jamespetts gb

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Re: Token block signals not clearing previous block
« Reply #1 on: June 10, 2018, 10:17:20 PM »
Thank you for your report. I think that I have now fixed this - I should be grateful if you could re-test and report the result with the next nightly build.

Offline Matthew

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Re: Token block signals not clearing previous block
« Reply #2 on: June 13, 2018, 12:05:42 AM »
I have checked this on the nightly from 12 June (#26ed33b) and the token block signals now seem to work as expected, without this pattern. Thank you for fixing this, James!