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 80% reduction in nitrogen oxide emissions. "See" List of low emissions locomotives. Other technologies that are being deployed to reduce locomotive emissions and fuel consumption include "Genset" switching locomotives and hybrid Green Goat designs. Genset locomotives use multiple smaller high-speed diesel engines and generators (generator sets), rather than a single medium-speed diesel engine and a single generator. Because of the cost of developing clean engines, these smaller high-speed engines are based on already developed truck engines. Green Goats are a type of hybrid switching locomotive utilizing a small diesel engine and a large bank of rechargeable batteries. Switching locomotives are