Following the successful 1939 tour of EMC's FT demonstrator freight locomotive set, the stage was set for dieselization of American railroads. In 1941, ALCO-GE introduced the RS-1 road-switcher that occupied its own market niche while EMD's F series locomotives were sought for mainline freight service. The US entry into World War II slowed conversion to diesel; the War Production Board put a halt to building new passenger equipment and gave naval uses priority for diesel engine production. During the petroleum crisis of 1942–43, coal-fired steam had the advantage of not using fuel that was in critically short supply. EMD was later allowed to increase the production of its FT locomotives and ALCO-GE was allowed to produce a limited number of DL-109 road locomotives, but most in the locomotive business were restricted to making switch engines and steam locomotives.