It has been several years since I saw the information, but from what I remember tests determined that a unit train of coal will lose about 10% of the load as dust and small particles between the mine and destination. At 10% then that would be the equivalent of losing 15 or 16 of those cars in transit that the customer is not receiving and the railroad is hauling empty cars for nothing.Unit trains of 100 ton cars are restricted to a maximum of 45 mph because of control and reducing damage to track and cars. It is interesting that an empty train causes more damage than a loaded one because the truck springs are set for loaded condition