Factorio Forums

Practicing trains before Space Age comes out. Trying to get a feel for rails. Do these signals make sense? Am I supposed to remove the two central chain signals so that no trains can enter or exit the intersection at all unless its clear?

The simple version:

• Use chain signals before shared track.
• Use normal signals after shared track.

That's it.

I think your tracks are way over-signaled.

Start by removing all the signals.

Then add chain signals before shared sections, and normal signals after.

Then maybe you want to add more normal signals to stack multiple trains, e.g. waiting for a train stop.

A slightly different way of looking at things but I think essentially the same as Kyralessa wrote:

Using unidirectional track, the basic approach I use for signalling a junction starts by placing a chain signal at every entrance and a rail signal at every exit. Entrances are the points before the first split or before the first time the track crosses another, and exits are the points after which the track only merges with other tracks or before train stops (or other places you may have trains wait). I've marked signal locations for entrances (blue) and exits (yellow) in a copy of your image (you have a signal missing to the south):
I also ensure that, from each exit signal, the distance to the next signal (in the direction of travel) is at least as long as the longest train. This means a train will only enter a junction when it is able to get its rear past the exit signal, so the junction is completely cleared.

Then I consider adding chain signals in order to improve throughput of the junction, by placing them to (a) split up blocks to allow non-conflicting paths simultaneously, and (b) release paths sooner. A rule of thumb is to place chain signals before a track splits or crosses another. It is usually highly desirable for paths of "straight through" trains travelling in opposite directions to not share any blocks. In other cases, adding a chain signal might have very little effect on throughput.

I may also consider replacing multiple rail signals before merges with a single signal after the merge, which can reduce the number of signals without impacting throughput significantly. For example, in your image, the rail signals before the east-to-north curve from the west stop and northbound track merge could be replaced with a single rail signal after they merge. However, if you did that, a chain signal would be needed between the southbound and northbound lines to allow a pair of trains to pass straight through without affecting each other, so it doesn't actually make sense.

It's worth noting that curved rails will be different in 2.0 (see FFF-377) which will change exactly where you can place signals. However, as far as I know signalling will work in the same way as it does now and the above will still apply.