TRains

[gah]

was wandering hpw t get the trains to stop wandering(Implicit)

[Alberth]

Make trains be able to go in any direction they want, at all junctions

They tend to visit depots as they see fit, trouble is they may not be able to get back to their original tracks in a logical way, so instead they find a much longer path, that they follow to get at their destination.
Another common reason is that you may have forgotten some track somewhere, so you think they should be able to use a shorter path, but in fact they can't.

Last but not least, if paths are mostly equal in length, they distribute the traffic over all paths, to increase throughput.