Back in bukkit times (1.6) i loved to play minecraft with a plugin called TrainCarts, which enables cartlinking and a simple routing system using redstone and signs. Using this mod, all minecarts linked together act like a single train, which can stop at stations and other amazing things.
According to Minecraft Wiki entry:
It was initially developed to link multiple carts together, creating a moving train. The physics got improved as much as possible, with the final result: A single moving entity.