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Locomotive Descriptions and Phases - ALCO RS-11

The ALCO RS-11 was introduced in 1956, replacing the RS-3 as ALCO's general-purpose four-axle road switcher. It used a 12-cylinder 251-series engine developing 1,800 horsepower, which proved more reliable than the earlier 244-series engine, and it was very similar in size and power to EMD's competing GP9 and GP18.

Typical RS-11 units could be identified by 2-axle Type B trucks and a clean-lined carbody, with full-height hood with large vertical radiator intakes at the end and a single large radiator fan. Most units had a rectangular chickenwire grill over the intercooler intakes covering an air cooling pipe manifold from the air compressor, along with a lengthwise fuel tank flanked on either side by an air reservoir under the walkway. A high short hood was initially standard; some later-production units were built with a low short hood. The hood corners had 45-degree notches for the number boards and classification lights.

A sister model produced in Canada, the MLW RS-18, was introduced at the same time. Both the RS-11 and RS-18 were an evolution of the earlier MLW RS-10, itself essentially an RS-3 with a redesigned frame and carbody. Externally, the RS-11 combined the general frame and carbody design of the MLW RS-10 with several features from the earlier ALCO RSD-7, including sharper cab edges and the hood corner notches. The cab roof was lowered compared to previous ALCO and MLW RS-series units to a height of 9' 1" above the frame; this height would be used in later RS and Century series production. For more details on the differences between the RS-11 and similar MLW RS-10 and RS-18, as well as many dimensions that apply to the RS-11, see MLW RS-10, RS-18 phases.

More than 400 RS-11's were built up to the middle of 1964, with ALCO production ending in 1961 and the last units built for export by MLW. It was replaced (ultimately jointly) by the very similar 2,000-horsepower RS-32, introduced in 1961, and the 1,800-horsepower RS-36, which arrived in 1962. While most RS-11's did not enjoy the 30- to 40-year service lives that MLW RS-18's had with CN and CP, most still saw more than 20 years of service with their original owners, and a number have remained in service into the 21st Century on smaller railroads.


I have based these phases on the RS-11 Roster compiled by David Thompson, with several additional details added as sub-phases of Thompson's original phases.

Phase 1a1 1a2 1a3 1b 1c1 1c2 2a1 2a2 2b 3
Dates 1956-02 -
1957-06 -
1958-04 -
1958-07 -
1958-11 -
1959-01 -
1959-04 -
1959-06 -
1960-03 -
1963-06 -
Corner handrails 1 Inward jog Straight, rounded top
Air reservoir supports 2 Attached to U-shaped connector below side sill Attached to straight connector with a notch in the side sill
Equipment box behind cab 3 Yes No
Radiator intakes 4 Narrow frame, 24 shutter vanes with no external clips, control box at top right corner Wider, bolted frame, 16 shutter vanes with external rod clips, control mechanism at top corner facing the cab
Phase 1a1 1a2 1a3 1b 1c1 1c2 2a1 2a2 2b 3
Coupler pocket 5 Cast Fabricated
Hood air intakes 6 2 separate intakes near cab (with dynamic brakes), 3 intakes in upper sections of center hood (all units) 3 grouped intakes near cab (all units), 2 intakes in 1st and 3rd sections of center hood (with dynamic brakes)
Handrail stanchions 7 Square, fastened to walkway with L brackets, angled braces at either end Cylindrical, fastened directly to walkway, no angled braces
Hand brake wheel 8 Recessed Surface-mounted
Hood, dynamic brakes Short doors, flat dynamic brake housing, square intakes above center doors
RS-32 style (built by MLW)Taller hood doors, shorter, rectangular intakes above center hood doors
Phase 1a1 1a2 1a3 1b 1c1 1c2 2a1 2a2 2b 3



These two drawings illustrate typical early (Phase 1a1) and late (Phase 2b) RS11's built to MEC and LV specs. The LV version has Hyatt roller bearings on the trucks (less common than Timken bearings) as well as the low short hood that appeared on a few late RS-11 orders.

Click on the links to toggle between the images.

Phase 1a1 -  Phase 2b

Railroad Variations


DWP RS-11's, numbered 3600-3614, were built to the same specifications as several of CN's RS-10 and RS-18 orders. They had transverse fuel tanks and air reservoirs, light-weight trucks cast by GSC (of the same design as those cast by CSF on MLW units), and dynamic brakes located in the short hood. The units alternated in service between CV and DWP, ultimately wearing at least nine different paint scheme variations. One unit, 3608, was rebuilt with a low short hood. Unit 3609:1 was wrecked and retired in 1980; it was replaced by 3609:2, a former NW unit.


Norfolk & Western RS-11's had several unique features. As-built, they had a compartment on the conductor's side next to the fuel tank for rerailers and chains and sanding control valves placed lower on the underframe than standard RS-11 production. The earliest units had nearly flush single square sand hatches on the top of the hood ends (in place of dual hatches in the hood corner notches) and no rooftop corner grabirons.

As early as the beginning of the 1960's, NW applied a number of modifications. The units received taller sand hatch housings; steps added in the corner notches of the long hood (and occasionally short hood); and grabirons on the upper hood corners. Intermediate orders (Phase 1c1 to 2a1 units, numbered NW 365-400) had notch steps and roof grabirons as-built. Soon afterward, the units received louvers over the hood air intakes and a revised sanding control system with individual pipes for each control valve.

On the last order of RS-11's from 1961 (NW 401-406) as well as the subsequent order of RS-36's (NW 407-412), the louvered intakes were present as-built, but the sand hatches were circular and the sand lines were the standard RS-11 design (with only the hose and vertical pipe visible under the hood ends).

Later, most if not all units had the rerailer/chain box removed, and a spare knuckle basked added on the walkway behind the cab. Some also had the MU connector housing relocated to the walkway instead of the end handrails.


Many Pennsylvania RS-11's were instantly identifiable by the prominent Trainphone antenna running the length of the roof and disc-shaped receiver on the short hood, along with a screen covering the radiator intakes. However, only half (PRR 8617-8635) were so-equipped; PRR 8636-8655 had neither the Trainphone antenna nor the radiator screens. Additionally, PRR 8626 and up had the larger version of the twin-beam Pyle headlight.


Canadian National Railways Historical Association. (2018). RS-11. Retrieved January 2019 from

CNRPhotos. 3600s - RS-11. [Photo collection]. Retrieved December 2018 from

Norfolk and Western Historical Society. (2019). Archives Database. [RS11 database search]. Retrieved December 2018 from

Thompson, D. Alco's RS11 - Original Owners. Retrieved January 2018 from