ALCO RSD-12
Ferrocarril del Pacifico 504 in Nogales, Sonora, Mexico, in March 1979
Type and origin Power type Diesel-electric Builder American Locomotive Company Montreal Locomotive Works Model RSD-12 Build date April 1956 – March 1963 Total produced 171
Specifications Configuration: ​  • AAR C-C Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Prime mover Alco 251B Engine type V12 Four-stroke diesel Aspiration Turbocharged Cylinders 12
Performance figures Power output 1,800 hp (1,300 kW)

The ALCO RSD-12 was a C-C diesel-electric locomotive rated at 1,800 horsepower (1.34 MW). 171 locomotives were produced —Used in much the same manner as its four-axle counterpart, the ALCO RS-11, though the six-motor design allowed better tractive effort at lower speeds.

Five examples survive today:

• NKP 329 is preserved as a museum display in Bellevue, OH.
• OERM 2954 (ex-SP 2954) and 2958 (ex-SP 2958) are preserved at OERM in Perris, California.
• PJS 7012 (ex-SP 2962) is preserved at the Arkansas Railroad Museum.
• Derelict LS&I 1804 rests in a shipyard in Escanaba, Michigan. Its prime mover was transplanted to a tugboat.^[1]

Original buyers