The Rapid Discharge Hopper, designed for heavy, dense loads like sand, gravel, limestone, and other aggregates, was designed and built by the Ortner Freight Car Co. (Now part of the TrinityRail® group). Thanks to its steep 60-degree end sheets and Rapid Discharge hopper door system, the car unloads completely in less than 30 seconds without the need for a car shaker. An entire unit train of these cars can be unloaded in 30 to 60 minutes, whereas other unloading systems could take 4 hours or longer. The design has stood the test of time, as these cars are still in service on many railroads nationwide.