I built a road depot to take food from the processing plant to the town. This was fine, but it's producing far too much for the horse wagons to transport. So, to help out, I built a train depot as this will be much faster. The problem is the processing plant is still dumping the majority of the food at the road depot. There are 20+ units waiting at the road depot, and 1-3 units being deposited at the train depot. The train picks these up, but it means it runs with short loads every time (I could wait until it's full, but I can see there are still loads going to road depot).
How do I force the processing plant to deposit the majority of the food at the train depot? I want a 75/25 split in favour of trains. (I have approx. 10/90 currently!)