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
Rigid-framed electric locomotive reluctant single prototype, built for comparison with the articulated 2′B+B1′ , which had themselves been a reaction to the poor performance of the 1912 1′D1′ . A rare example of the 2′D2′ layout was the unique British diesel-mechanical of 1955. Rigid-framed electric locomotive Rigid-framed electric locomotives were some of the first generations of design. When these began the s of these early locomotives, particularly with AC motors, were too large and heavy to be mounted directly to the axles and so were carried on the frame. One of the initial simplest wheel arrangements for a mainline electric locomotive, from around