Factorio Forums

I'm experimenting. In this diagram, with the trains in the positions shown:



Where would I place chain signals so that the two circled signals become red (but the rest of the signals remain as they are shown)?

That is, to prevent a train at one of the two stations on the right from entering that intersection while there's a train sitting at the station on the left.

Essentially I want the top signal in each pair on the right to always be the same as the top signal in the pair on the left.

I read the wiki (and the "Friday tips" thing and watched some tutorials) about chain signals and thought I understood them, but I've tried every combination I could think of and am unable to turn those two signals red. My understanding is that chain signals can help prevent a train from entering a block when the train currently in the block has no other exit, but I can't figure out how to apply it.

Oh wait I figured it out. I think the act of taking a break to write this post helped me get a fresh look. The way to make it work is to use chain signals instead of the two circled signals. This works great (each train goes back and forth between the left station and one of the right stations):

Rubber duck debugging in progress...

twepy wrote:Rubber duck debugging in progress...

I think about 90% of the total crap I've posted to the internet has been me using the internet as my duck. I should get a real one. A real rubber one I mean. Or a real duck. Whatever.

With intersections in general, you want chain signals on any entrance into the intersection (as well as and crossings) and normal signals on the exits of an intersection.


So in the intersection above, you would would also want a chain signal on the bottom of the tracks before the Y.

or more generally on every signal you don't want a train to wait at go back an change every signal leading to that signal to a chain signal.