This category lists all the diesel electric locomotive classes of Indian Railways. According to IR nomenclature, classes prefixed with 'W' run on the 5 ft 6 in (1,676 mm) broad gauge and those prefixed with 'Y' run on the 1000 mm metre gauge. The second letter denotes the power type which is 'D' for diesel in all these cases. The third letter describes the type of service with 'G' for freight/goods service, 'P' for passenger service and 'M' for both. 'S' is for shunting locomotives