The ALCO RS-11 is a diesel-electric locomotive of the road switcher type rated at 1,800 hp (1.34 MW), that rode on two-axle trucks, having a B-B wheel arrangement. This model was built by both Alco (355 units) and Montreal Locomotive Works (76 units). Total production was 431 units.
The first three RS-11s were produced by ALCO in February 1956 as a demonstrator set. This locomotive, classified by ALCO as model DL-701, was their first high-horsepower road switcher, intended to be a replacement for the very popular RS-3 road switcher. Featuring a V-12, 1,800 hp (1,300 kW) 251B diesel engine, the RS-11 was ALCO's answer to EMD's very successful GP9. The turbocharged RS-11 accelerated faster, had a higher tractive effort rating and typically used less fuel than the competition. It was also quite versatile and could be found in heavy haul freight as well as passenger service. It was produced in high-nose and low-nose versions. Montreal Locomotive Works also built nearly identical units, known as the RS-18, predominantly for the Canadian market.
While the RS-11 benefited from the increased power and reliability offered with ALCO's new 251B engine, and was arguably a more advanced product than the GP9, its market acceptance was disappointing against the reputation EMD's locomotives had made for superior reliability.