11-25-2010, 10:25 AM
I have just one point of clarification to add. Not all cars puled from an industry will go to interchange. Certainly all loads will be interchanged to be sent off site to their destinations, but empties may be held in the yard waiting for a local industry to need that type of car for a load out. If too many empties "pile up " in the yard, then some would be interchanged. Also if a car is in dedicated service to be used between two designated industries, it would be sent back asap. An example of this from the past would be ice bunker cars. Back before the interstate highway system, most produce was shipped to the East from California in SFRD or PFE cars. Once unloaded, they were restricted as to type of freight that could be shipped back in them, and the S. F., U.P., or S.P. wanted them back for reload asap.