Of particular interest to many observers were the Military Road Switchers designated MRS-1 and built specifically for the US Army Transportation Corps. These engines were constructed by the Electromotive Division of General Motors and by the American Locomotive Company (Alco) with trucks that could adjust to accommodate selected track gauges between and broader gauges up to . The reason for this was the potential use of these locomotives on the railroad networks of Europe and the USSR where broader gauges precluded the use of unmodified US locomotives in the event of a major war. While built to the same specifications, there were external differences between the EMD and Alco MRS-1s as can be seen in the rooflines.
