Let's look at another variant, where the train has an ordering. We have a locomotive, painted black, and three blue cars. In the resulting position, the place where the locomotive should go is depicted in gray, and the car places in light blue.
We return to our initial graph shown in the first example. Remember that any two 4-paths can be transformed into each other in at most 10 steps. In the oriented case, for the two positions below we need 14 moves.