I have used RailOp for several years and have been very pleased with the operations. It is ideal for a single operator or a large Op session group. After all your setup data has been entered (cars, locations, track lengths, routes, trains, etc.), it randomly generates manifests for all your trains as you select them. The manifest will show what cars to build the train with, all the stops along the way with drop-offs/pick-ups, which track to put the cars on. Cars are placed only on tracks designated for that type of car and only if the track has space. Really a good program. http://www.railop.com/index.php?main_page=index
Hope it helps you out.
You may want to take a look at their forum. You can search your questions or just ask. There have been many interested in the program, but want to clarify certain aspects of its capabilities and how-to's. .