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
Diesel locomotive fully insulated electrical system (neither side earthed to the frame) and all electric wiring enclosed in conduit. The flameproof diesel locomotive has replaced the fireless steam locomotive in areas of high fire risk such as oil refineries and ammunition dumps. Preserved examples of flameproof diesel locomotives include: Latest development of the "Flameproof Diesel Vehicle Applied New Exhaust Gas Dry Type Treatment System” does not need the water supply. The lights fitted to diesel locomotives vary from country to country. North American locomotives are fitted with two headlights (for safety in case one malfunctions) and a pair of ditch lights. The