Diesel locomotive were classified as DET 1 and DET 2 (). Due to shortage of petrol products during World War I, they remained unused for regular service in Germany. In 1922, they were sold to Swiss Compagnie du Chemin de fer Régional du Val-de-Travers (), where they were used in regular service up to the electrification of the line in 1944. Afterwards, the company kept them in service as boosters till 1965. Fiat claims a first Italian diesel–electric locomotive built in 1922, but little detail is available. A Fiat-TIBB diesel–locomotive "A", of 440CV, is reported to have entered service on the Ferrovie
Steam diesel hybrid locomotive diesel engine was directed into a large-diameter steam cylinder. There was no boiler: instead a pump, operated by a cam driven from the common crankshaft, injected water (warmed by the diesel cylinder water jacket) into the steam cylinder so that it was instantly evaporated by the hot exhaust gases, powering the piston by expansion. Again, no operational examples are known. Steam diesel hybrid locomotive A steam diesel hybrid locomotive is a railway locomotive with a piston engine which could run on either steam from a boiler or diesel fuel. Examples were built in the United Kingdom, Soviet Union and Italy