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.
Diesel locomotive
Before diesel power could make inroads into mainline service, the limitations of diesel engines circa 1930 - low power-to-weight ratios and narrow output range - had to be overcome. A major effort to overcome those limitations was launched by General Motors after they moved into the diesel field with their acquisition of the Winton Engine Company, a major manufacturer of diesel engines for marine and stationary applications, in 1930. Supported by the General Motors Research Division, GM's Winton Engine Corporation sought to develop diesel engines suitable for high speed mobile use. The first milestone in that effort was delivery in early 1934 of the Winton 201A, a two-stroke, Roots-blown, uniflow-scavenged, unit-injected diesel engine that could deliver the required performance for a fast, lightweight passenger train. The second milestone, and the one that got American railroads moving towards diesel, was the 1938 delivery of GM's Model 567 engine that was designed specifically for locomotive use, bringing a fivefold increase in life of some mechanical parts and showing its potential for meeting the rigors of freight service.