This variant was designed for service on light track, as the extra axles better spread the weight of the locomotive.

[citation needed] In the end, EMD won the road switcher production race.

[citation needed] In 1952, the Brazilian railway the Estrada de Ferro Central do Brasil purchased forty six new RS-3s from the Montreal Locomotive Works.

Some are still active as work train engines for CPTM, Supervia, and CBTU – BH respectively São Paulo's, Rio de Janeiro's and Belo Horizonte's commuter railways.

[citation needed] In 1964, the Spanish railway the Ferrocarril de Langreo purchased four RS-3s from the Terminal Railroad Association of St. Louis.