Dieselisation
Dieselisation took place largely because of the tremendous reduction in operating costs it allowed. Steam locomotives require large pools of labour to clean, load, maintain and run. They also require extensive service, coaling and watering facilities. This was their biggest inferior measure as compared to the diesel locomotive in the number of ton-miles or passenger traffic miles either could run. Diesels could and did have a significantly higher initial price per unit-horsepower delivered. However, their far greater range between fueling stops, the absence of water stops, and the much higher unit availability between inspection repair and maintenance stops, were far better than steam. Diesels simply required significantly less time and labour to operate and maintain. Diesel power was also more scalable to power requirements, owing to the control systems that allowed multiple units to be controlled by one operator. "Double header" steam power required a crew for each locomotive. Initially, diesel locomotives were less powerful than the typical steam locomotives. Between the late 1930s and the late 1950s the power available with diesel locomotive engines roughly doubled, although the most powerful steam locomotives ever built still exceeded the power of the most powerful diesel locomotives from the late Twentieth Century.
Electro-Motive Diesel
Passenger trains made little money for the railroads, but replacement of steam engines with reliable Diesel units could provide railroads with a crucial difference for profitability. With standardized production of locomotives, EMC simplified the processes for ordering, manufacturing, and servicing locomotives and introduced economies of scale that would lower unit costs. EMC offered support services including financing, training, and field maintenance that would ease the transition from steam to Diesel and boost their market in the last years before US entry into World War II. The performance of the new 567 engine in passenger locomotives also built confidence in the viability of Diesel power for freight service.