I think I understand it better now, the depot is the waiting station. It cycles the waiting train through all resources. Now you're a coal train, now you're a rocket fuel train, and so on. Only if the (temporary) coal train finds an available coal provider, it leaves. That way, not all trains look ...

Hi, this is excellent thanks! I was looking at the overprovisioning issue that this solution still has issues with.
(If multiple providers exist and a single requester is enabled, then multiple trains are dispatched in the single tick before the providers disable themselves)

It can be fixed with ...