Factorio Forums

TL;DR

Train signals that increase train pathing costs, so that could build main train highways and have trains use them instead of cutting through blocks for a shorter path.

What?

A new type of train signal that increases the pathing cost of a train route that crosses it. Could be configured to not impose the pathing costs on certain trains depending on conditions of the train such as the name, destination stop (specific instance or name), origin stop (specific instance or name) or cargo.

Why?

When building a train based factory logically it would be a good idea to have arterial rail lines (multiple tracks in both directions) for trains that need to go across the factory and local rail lines (one track in each direction or even just a single direction loop) for short distance travel such as to a neighbouring block. In practice however trains will often cut through local lines to get a shorter path to their destination clogging up the lines designed for lower throughput. By artificially increasing the pathing cost of entering (or transfering between) the low throughput lines long distance travel and shortcuts through them will become unfeasible as the pathing costs will rise faster than using the high throughput arterial lines.
If the costs could be waived depending on the train's destination it could be setup so that trains that are heading to a stop within a low throughput area can enter it freely without incurring any extra pathing cost possibly optimizing the search algorithm

You can get this now with two signals like 2m apart, wired together. The front one's set to read red on either red or green, the rear one's set close-if red>0. So pathing through it is penalized except for the one tick where the front signal's reserved and it itself isn't yet. For times where you want even more control there's an efficient force-a-repath gizmo in the "Automatic Train Cyclotron" thread.