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Question regarding junctions and path'ing

Posted: Tue Jun 09, 2020 1:08 pm
by Nibenay
Hi all,

I have been looking into making a 4 lane rail (2 each way) for a larger base. I did find some blueprints that seemed good, but at closer inspection, some of their junctions even block parallel going trains, which I wanted to remove.

Trying to make a junction that allows for all incoming trains to go in all directions - while at the same time it can have 4 trains running in parrallel, I ended up with this:
4wayjunction.PNG
4wayjunction.PNG (2.18 MiB) Viewed 1763 times
It's bascially that every incoming line first branches 2 times to right, then two times to right. All are chain signals except the exits.
To my limited understanding, having everything chain signaled should cause an incoming train to reserve a path. If we started the 4 trains placed there now, they should all head straight and leave without issues. Naturally if a train has to turn, some section will be blocked in some way.

However afterwards I basically had made a giant roundabout....

the trains will have length 6(1-4-1) and length 22(8-16). Since we're playing bobs, the long train might be shortened later on when we get the higher MKs with more power.

1) do I understand the pathing correctly? To my knowledge they should reserve paths that are several train-lengths ahead, making a deadlock unlikely and allow parrallel trains to keep running.
2) I see repathing mentioned, which certainly would be an issue here, does this happen frequently?

3) Is the roundabout part likely to cause issues?
4) It doesn't line up nicely to the grid - is this relevant and if so what situations would that be important?

Blueprint:


Thanks in advance :)

Re: Question regarding junctions and path'ing

Posted: Tue Jun 09, 2020 1:16 pm
by Koub
[Koub] Moved to Gameplay Help
Also @OP, this might help you : viewtopic.php?f=194&t=46855

Re: Question regarding junctions and path'ing

Posted: Tue Jun 09, 2020 6:11 pm
by Nibenay
Thanks for the link. I've already looked at it before and the designs are interesting. As far as I can see, the most efficient and deadlock free simply map one input to the corresponding output, with no lane switching or U-turns.

However I can't see that the more compact junctions are so different to the silly one I made (lets disregard a few missing signals already), as I'm not going to make 22-wagon long buffers part of the junctions anyways :P
As far as I see, as long as one train has already reserved a path through, others will either have to wait, or going in a non-crossing path anyways.

well will overpasses be implemented.. :(

Re: Question regarding junctions and path'ing

Posted: Wed Jun 10, 2020 4:27 pm
by Ranger_Aurelien
Nibenay wrote: Tue Jun 09, 2020 6:11 pm well will overpasses be implemented.. :(
I have used these:

https://mods.factorio.com/mod/rail-bridge

https://mods.factorio.com/mod/traintunnels

Re: Question regarding junctions and path'ing

Posted: Wed Jun 10, 2020 10:55 pm
by Nibenay
Are they working well?
I've seen the bridge one earlier, but I also read these kind of mods are very unstable. The second one even mentions it in the description.