Although built in 1949, this design dated back to 1944, and included three models; DRS-6-4-1500 (Diesel Road Switcher, 6 axles, 4 traction motors, 1500 horsepower), DRS-4-4-1500, and DRS-6-6-1500. It was powered by Baldwin's 608SC (SC = SuperCharged, or today, turbocharged) diesel prime mover driving a Westinghouse 489-B main generator powering six Westinghuse 370 series traction motors. To make room for the middle traction motor, the center axle was offset. The long hood was considered the Front of the locomotive. The C&NW placed the order for the first production DRS-6-6-1500's in 1948, and by 1952, the 608SC prime mover was replaced by the 608A, and the DRS model was replaced by the AS model. The final tally was; 91 DRS-6-4-1500's (62 for export), 35 DRS-4-4-1500's (3 for export), and 83 DRS-6-6-1500's (all domestic).