I'm curious as to how real railroad do this: When the local rolls into town, do they usually pick up all empty cars, even if they're not dropping a new loaded one off, or do they just leave it until they have a drop off? Also, I'm modeling a dead end branch line so this question is geared for that. For example: A westbound local goes by the elevator and needs to pick up 10 loaded hoppers and drop off 10 empties. Its the only stop in that town. Do they do the swap, or just drop off the empties and pick up loads on the way back by? Or go right on by and swap on the way back?