The unit train concept was pioneered by Ortner Freight Car Co. in 1960 as an effort to streamline bulk cargo unloading. Robert Ortner, developer of the rapid-discharge door system, targeted unloading a train of rapid discharge cars in 30 minutes to an hour.
Previously this same task would take four hours or longer. Unit trains shuttle back and forth between mines and power plants eliminating dwell time in yards. The concept has become ubiquitous to the modern railroading scene.