Talk:Train Signals

Proposed paragraph
I proposed to add this paragraph to the Tips section:

With block signals, two trains can enter a block at the exact same time and collide. This might be considered a bug. It is generally possible (and intended) to organize your track so that path signals, and not block signals, are used whenever there are multiples entries into a block.

Got the reply "need verifiable proof as this is a pretty major claim". So here are two sources for this claim:

1. The same page already contains a paragraph starting with "WARNING" which mentions the same problem. My point of repeating the information in the "Tips" section is to clarify that the claim made there, "Collisions generally shouldn't happen if any signals are in place. Gridlocks may occur instead", is not quite correct.

2. https://questions.satisfactorygame.com/post/62ad0e51ca608e0803514f86 with a save file that shows the problem.


 * Thanks for backing this up! I moved the collision issues into a Current issues section and linked the QA site post as reference. Let me know if it fits or needs further adjustments. --Ondar111 (talk) 10:19, 19 November 2022 (UTC)

Another way to get train collision
The section "Train collisions can occur even with seemingly properly placed signals" could also mention this way: locomotives and wagons are considered to be inside only one block at a time, as determined by their center. It's possible to have a block that is just the wrong length. Say you have a train with 1 locomotive and 2 wagons, each 1 unit long, and a block whose length is 2.8 units. The train will enter the block, and stop if the exit is red. At this point, the last wagon is still not completely inside the block, but its center is, and so the block behind is considered free. The next train can enter the block behind, and slow down, but still collide with the end of the previous train. It might generate collisions that are soft enough that the trains don't derail, in which case there is no issue, but in some cases the collision can be hard.