Station balancing / train pathing question

[Serenity]

I know you can disable stations or signals so that trains go the one with the least material. I'll probably do that in the future. But how does that work with the railway track layout and pathing?

Let's say I have two stations. If the train leaves the iron mine it can pick easily. But then it gets past station A (which is closed) towards B. Now B gets filled from a train already there and is closed. Where is the train supposed to go? Am I just supposed to provide a loop at the end of the feeder line, so the train can turn around and head back to station A?