https://wiki.mcjty.eu/mods/index.php?title=Basic_Structure#Subways

Currently, the subway systems only run east-west over any significant distance, with some tracks oscillating slightly north and south as they do so. We should add some subway tracks that run north-south over long distances. We could either make these new tracks on a lower level, or use detector rails and some redstone to set up automated switching to keep carts going where they're supposed to go.