Automatically places rail (chain) signal on rails on the (mostly) correct places. Will mark existing signals for deconstruction/upgrade if needed, and places ghost signals where needed.
I do heavily recommend to check the signals after using the planner. Do not fully rely on it as it might not be optimal (or just not possible at all to be optimal)
The planner is found on the shortcut bar (ALT + S by default, can be changed in the control settings), and in the blueprint library.
How to use
Place a single rail (chain) signal on the track to indicate their direction.
Then drag the planner over the rails to place rail signals and chain signals ghosts on the correct places.
It will mark any incorrect signals for deconstruction or for upgrade.
When placed in your inventory you can set max train length (to indicate how much space should be left free after a crossing) and the rail signal distance (the distance signals should be placed apart from at long stretches. By default it is set to 8, the distance they can be on a curved rail.)
You can also choose the rail and chain signal to use for modded signals.
Placement of signals is not always perfect (sometimes there are some chains that could've been rail, or two consecutive chain signals), but it should prevent any deadlock, while still maintaining decent throughput.
Full album, if you're on pc and don't want to open every video individually
It removes all signals on a bidirectional rail, except for at crossings
A simple crossing
Two way crossing
Two way intersection
It checks the direction of a rail based on the existing rails. If there are no signals in front or behind a rail, it marks it as bidirectional, so sometimes you need to drag over twice if your first signalling wasn't quite complete yet.
One way to bidirectional
One way to bidirectional while holding shift
Normally it ignores all double signals. When holding shift it doesn't ignore them, so it marks all rails in front and behind of it as bidirectional.
LeonSkills - author
Medium9 - German translations
Badway - Russian translations