Diesel locomotive Dv12s. In the 21st century series production standard gauge diesel–hydraulic designs include the Voith Gravita, ordered by Deutsche Bahn, and the Vossloh G2000, G1206 and G1700 designs, all manufactured in Germany for freight use. Steam-diesel hybrid locomotives can use steam generated from a boiler or diesel to power a piston engine. The "Cristiani Compressed Steam System" used a diesel engine to power a compressor to drive and recirculate steam produced by a boiler; effectively using steam as the power transmission medium, with the diesel engine being the prime mover The diesel-pneumatic locomotive was of interest in the 1930s because it
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