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 was not developed enough to be reliable. As in Europe, the usage of internal combustion engines advanced more readily in self-propelled railcars than in locomotives. Unlike steam engines, internal combustion engines require a transmission to power the wheels. The engine must be allowed to continue to run when the locomotive is stopped. A diesel–mechanical locomotive uses a mechanical transmission in a fashion similar to that employed in most road vehicles. This type of transmission is generally limited to low-powered, low speed shunting (switching) locomotives, lightweight multiple units and self-propelled railcars. The mechanical transmissions used for railroad propulsion are generally more