General Motors' diesel-electric locomotives had proved themselves in the US and Canada before the war. DSB's class MY A1A-A1A diesel locomotives, built on license from GM and delivered from NOHAB starting in 1954, were found to be very reliable and economically feasible compared to the steam locomotives, eventually putting the age of steam to an end as well as being a decisive factor in DSB's choice of motive power for nearly three decades. They were followed by the equally successful class MX with a lower axle load for branch line services and the class MZ for heavy express services.