Factorio Forums

While testing an issue someone was having with signaling a roundabout (no, I don't recommend them, but some people still like them) I found that even after all normal signals at the exits turn green, the chain signals remain blue because they all can see a blue chain signal, so they disregard the fact that none of them can see any red regular signals anymore.

I assume this is an optimization where each chain signal only has to check as far as the next signal ahead of it, but it prevents a roundabout (or other looped track) from resetting back to fully green.

I tried it with four chain signals on the horizontal/vertical joins, four on the diagonals, and with eight, and it made no difference.

Before train passes through

After train

In order to reset them all to green you have to break a track so that one of the chain signals along the loop can only see a green regular signal.

I don't believe this actually blocks any traffic, so it seems like a minor (but confusing) display issue. It should be possible to check for such a loop condition whenever a chain signal sees another signal switch from red to green (or blue) in order to trigger a reset to green when appropriate.

It makes perfect sense that it works like this.

I do agree it's confusing, though.

The colors have actually no effect on the logic, but this is deffinitely a bug.

I wont say it's a bug:
The pre-signals show green, when all following signals are green;
they show red, when all following signals are red
and blue, when there is (at least) one blocked and one free signal (blue signals count afait as partional blocked).

Within the loop, each pre-signal basicaly checks its own status (that is blue once the trains runs through)

Fixed for next release.