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.
Dieselisation
Competition from diesel spurred a round of development in steam locomotive technology. High style, high speed "steamliners" produced during the second half of the 1930s became the speed kings of passenger service. Duplex and articulated steam locomotives built in the early 1940s exceeded the power of any diesel ever built, although their power was edged by gas turbine-electric locomotives during the 1950s. But the limits of steam technology were rapidly being reached. The new locomotives were mechanically complex and extremely specialized. Locomotive size became an issue, as steam engines became so big in the 1940s that the cylinder and boiler dimensions were pushing the limits that the loading gauge would allow. Fireboxes became so big that firing a steam locomotive became an extremely difficult job without the aid of mechanical stokers. Mechanical stokers for feeding coal to locomotives were in use in the 1920s. Steam turbine-electric locomotive power was developed in 1938 by General Electric. GE abandoned the project in 1943 after results were unsatisfactory during trials with three railroads, however, Baldwin Locomotive Works built three steam turbine-electric locomotives in 1948. They were expensive to operate and insufficiently reliable for their intended service, and were scrapped in 1950. Baldwin's steam turbine-electric program resulted in one more locomotive in 1954, which was also not successful in service.