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 engine
Diesel engines may be designed as either two-stroke or four-stroke cycles. They were originally used as a more efficient replacement for stationary steam engines. Since the 1910s they have been used in submarines and ships. Use in locomotives, trucks, heavy equipment and electricity generation plants followed later. In the 1930s, they slowly began to be used in a few automobiles. Since the 1970s, the use of diesel engines in larger on-road and off-road vehicles in the US increased. According to the British Society of Motor Manufacturing and Traders, the EU average for diesel cars accounts for 50% of the total sold, including 70% in France and 38% in the UK.