Diesel locomotive Calabro Lucane in southern Italy in 1926, following trials in 1924-5. In 1924, two diesel–electric locomotives were taken in service by the Soviet railways, almost at one time: In 1935, Krauss-Maffei, MAN and Voith built the first diesel–hydraulic locomotive, called V 140, in Germany. The German railways (DRG) being very pleased with the performance of that engine, diesel–hydraulics became the mainstream in diesel locomotives in Germany. Serial production of diesel locomotives in Germany began after World War II. In many railway stations and industrial compounds, steam shunters had to be kept hot during lots of breaks between scattered short tasks.
Diesel locomotive provide the power needed on a heavy train. With steam traction a single very powerful and expensive locomotive was required for the heaviest trains or the operator resorted to double heading with multiple locomotives and crews, a method which was also expensive and brought with it its own operating difficulties. Diesel engines can be started and stopped almost instantly, meaning that a diesel locomotive has the potential to incur no fuel costs when not being used. However, it is still the practice of large North American railroads to use straight water as a coolant in diesel engines instead of coolants