BACK in the late 1860s, the concept of shippers owning freight cars was established with petroleum tank cars, but the concept spread. Mileage allowances were granted by the railroads in return for them not having to own the cars. As the ICC and other regulatory groups stepped in to specify what they expected in a freight car's design, a triangular relationship was established. Carmakers learned to build cars that both met the needs of the shipper and follow the dictates of safe car design. Shippers learned how to load and unload cars at each end using specially designed facilities, and railroads learned how to handle privately owned cars. The covered hopper is a case in point. First, the hopper stepped away from the flat car design by creating permanent unloading hatches of varying designs in the bottom of the car. This allowed the car to be loaded rapidly on the top and unloaded just as quickly out the bottom. To help expedite this process, special facilities were constructed at each end, and railroads learned how to handle long strings of nearly identical cars tor even greater efficiency.
