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.
0-6-0+0-6-0
The only steam locomotive example of this type of engine in the United Kingdom was the Leader. It was originally commissioned by the Southern Railway but it was completed by British Railways in 1949. The locomotive was a class of experimental articulated steam locomotive, produced in the United Kingdom to the design of the innovative engineer Oliver Bulleid. The Leader was effectively a Meyer locomotive since both sets of drivers were articulated. It was built in an attempt to extend the life of steam traction by eliminating many of the operational drawbacks associated with existing steam locomotives.
The 0-6-0+0-6-0 configuration was also applied to diesel-electric locomotives when British Rail created the Class 13 in 1965. This was done by permanently coupling two Class 08 0-6-0DE shunting engines as "master and slave" units, the latter with its cab removed. In North American terminology, this is referred to as a "cow and calf" arrangement. The modification came about because of a need to provide more powerful shunting locomotives for the Tinsley Marshalling Yard.