[0.17.66] Trains waiting at regular signals do not try to Repath every X seconds ?

[BlueTemplar]

N.B. : https://wiki.factorio.com/Railway/Train_path_finding

This situation feels like a bug :

dual-train_no_repathing.png (3.37 MiB) Viewed 1793 times

I would expect the green train to try to Repath after a while : switch to the other side-facing locomotive, and go to the other (identically named) vertical Green stop.
It never seems to.

Scenario :

dual-train test.zip

(386.5 KiB) Downloaded 82 times

(To reproduce, you'll have to somehow temporarily disable the other path, for instance by removing a rail in the hazard-concrete marked space.
In a regular base this can happen by simply having a third train passing through that segment at the same time that the green train tries to Path through it, making it temporarily unavailable.)

[boskid]

Once train chooses direction it wants to travel to destination (for example: when changing from manual to automatic or after full stop at previously reached station), it will only repath in same direction. If you toggle green train into "manual" and then again into "automatic", it will choose to go in opposite direction to reach second "Green" station ([-15, 5]). I am curious if this will be marked as "not a bug" or if will be fixed.

[BlueTemplar]

With a chain signal, the train does repath after a few seconds in the other direction.

However, while I now know about this trick, it took me a while to figure it out.
(P.S.: And one might not be able to use it in all situations, considering how chain signals... chain ?)

And new players, that don't like digging for the exact game mechanics, might be stumped by this behaviour.
(P.S.: They are also more likely to use single tracks with two-sided trains than more experienced players...)

[Loewchen]

Trains waiting at a closed regular signal is a very common occurrence, forcing them to repath every few seconds in the off chance that they can find a better route by going backwards the way they came makes absolutely no sense to me.

[BlueTemplar]

I'd settle on :

• If the trains has waited for a multiple of 30 seconds or if multiple train stops with the name of the destination exist, the train is forced to recalculate its path.

[BlueTemplar]

Also note that this is a situation with one (2-stop) Green station, but one could have two (or more) Green stations, hoping to send a stuck train to a better station elsewhere (on the same loop in this screenshot, but you get the idea...), but getting stuck anyway :

dual-train_no_repathing_multiple_stations.png (3.5 MiB) Viewed 1741 times

I guess that whether this is considered a bug or not will rather depend on how viable the devs consider dual-headed train networks to be ?

[mrvn]

This hopefully-a-bug mans your train track should probably look like this:

double-train.png (554.39 KiB) Viewed 1714 times

Which is a pain to build because you have to place a chain signal first, then you can place both full signal and finally you can place the second chain signal.

[Rseding91]

Thanks for the report however this is working as intended: trains stopped at normal signals explicitly do not do the repath-check logic.

[mrvn]

If it's a matter of saving cpu time this could be limited to special cases:

1) bidirectional train, if the train can't go backwards then there is no point
2) bidirectional signal, if the track is uni-directional again no point
3) only do this every 30 seconds, that should be rare enough