Montreal Locomotive Works (MLW) built these Bo-Bo type engines between December 1956 and August 1968 under license from the American Locomotive Company (Alco). The RS-18 was powered by a 4-stroke V12 diesel rated at 1,800 hp (1,340 kW). It replaced the RS-10 in MLW's catalog and production totalled 351 units to 8 customers, of which PGE took 29.
Canadian National Railway, by far the largest buyer of the RS-18, continued to specify the long hood as the front. By contrast, while all of Canadian Pacific Railway's RS-10s were long-hood-forward, all of their RS-18s were short-hood forward. All of CN and CP's locomotives were delivered with full-height short hoods, as were the first four Pacific Great Eastern Railway, and first Roberval and Saguenay Railway unit. The remaining production was for unitss with a low short-hood, giving the train crew much better forward vision.













