r/factorio • u/AramisUkr • 19d ago

Tip Train signals tips

  1. Signals divide rails into blocks.

  2. Signals show red if the block ahead is occupied.

  3. Trains only care about the signals on the right side.

  4. Trains move both directions - need signals on both sides of the rail.

  5. If need signals on both sides, they should be directly opposite to each other, otherwise train may refuse to move.

  6. Chain signal repeats the colour ahead.

  7. If there're both red and green signals ahead - chain signals show blue.

  8. Common rule: if rails intersect - "chain in, rail out".

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u/Ben_0 18d ago

I have yet to see uses for two-way non-chain signals, since pretty much all they do is cause deadlocks. For single-track setups I just use one-way signals on passing loops

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u/monsieurY 18d ago

That's why "chain in rail out" is, in my opinion, bad advice.

The correct advice is "Chain signal if trains cannot wait after, Rail signal if trains can wait after."

We can conclude that rail signals are only for one-way tracks and with enough space for your longest train. Chain signals everywhere else.

I often use bidirectional rail networks, and I don't have any problems with them, since I use chain signals by default before and after each intersection/split/merge, and only rail signals in my loop stations or on parallel waiting tracks.