Mosaic 212, an EMD MP15DC --Brewster, Florida.
|Builder||Electro-Motive Division (EMD)|
|AAR wheel arr.||B-B|
|Gauge||4 ft 8 1⁄2 in (1,435 mm)|
|Trucks||9 ft 0 in (2.74 m)|
|Wheel diameter||40 in (1.0 m)|
|Length||47 ft 8 in (14.53 m)|
|Width||10 ft ¾ in (3.067 m)|
|Height||15 ft 0 in (4.57 m)|
|Locomotive weight||248,000 lb (112,000 kg)|
|Fuel capacity||1,100–1,400 US gal (4,200–5,300 l; 920–1,200 imp gal)|
|Prime mover||EMD 12-645E|
|Aspiration||Roots type supercharger|
|Traction motors||4 × D77/78 DC|
|Power output||1,500 hp (1,100 kW)|
The EMD MP15DC was a 1,500 hp (1,100 kW) switcher-type diesel locomotive model produced by General Motors' Electro-Motive Division between March 1974 and January 1983. 351 examples were built. A MP15AC variant, with an AC drive, was also offered. Between August 1975 and August 1984 246 MP15ACs were built, including 25 for export to Mexico, and four built in Canada. The MP15DC replaced the SW1500 in EMD's catalog, and is superficially very similar to the predecessor model, using the same engine (a V12 EMD 645-series powerplant) in a similar design of hood and bodywork. The primary difference is the MP15’s standard Blomberg B trucks.
Switchers up to the SW1500 had been restricted to AAR type A switcher or Flexicoil lightweight trucks, both with a 96” wheelbase. In 1973 60 special order Mexico-only SW1504s were built on a slightly longer frame, allowing EMD’s standard Blomberg B trucks, with a 108” wheelbase, to be used. In EMD's eyes (among others) this made the new locomotive a road switcher rather than a pure switcher, since it was capable of transition and road speeds up to 60 mph (100 km/h) or so. The new model MP15DC designation thus meant Multi-Purpose locomotive, 1500 hp, DC generator. Originally the locomotive was simply designated the MP15; the arrival of the alternator/rectifier MP15AC in 1975 changed the name.
With the success of the MP15, there was a demand for a model with an advanced AC drive system. The MP15AC replaced the MP15DC’s DC generator with an alternator producing AC power which is converted to DC for the traction motors with a silicon rectifier. The MP15AC is 1.5 ft (457 mm) longer than an MP15DC, the extra space being needed for the rectifier equipment. The alternator-rectifier combination is more reliable than a generator, and this equipment became the standard for new diesel-electric locomotive designs.
The MP15AC is easily distinguished from the DC models. Instead of the front-mounted radiator intake and belt-driven fan used on all previous EMD switchers, these have intakes on the lower forward nose sides and electric fans. Side intakes allowed the unit to take in cooler air, and the electric fans improved a serious reliability issue found in its earlier DC sisters.
The MP15 used a 12 cylinder version of the 645E series engine developing 1500 hp at 900 r.p.m. Introduced in the SW1500, this was a supercharged 2 stroke 45 degree V type, with a 9" bore by 10" stroke, giving 645 cubic inches displacement per cylinder. The 645 series, introduced in 1966, was EMD’s standard engine through the 1980s. 
Early railroad buyers were the Pittsburgh & Lake Erie, with 25, and the Missouri Pacific, who would buy 62 between 1974 and 1982. The Chicago & Northwestern (15), Southern Pacific (12), Louisville & Nashville (10), and Reading (10) made smaller orders. Later, from 1977 to 1982, Southern bought the largest fleet, 160 units under six names. Over 50 more were sold to 37 other customers. .
In the early 1970s railroads were starting to convert to AC power, the six largest buyers, Milwaukee (64), Southern Pacific (58), Seabord (40), Nacionales de México (25), Long Island (23), and Louisville & Nashville (10), were all buying AC road locomotives. 36 more units were sold to 8 other customers.
The Union Pacific Railroad is perhaps the largest current user of the MP15DC, having 102 of the type in service (Strack, 2004). None were originally owned by the UP; instead, they were acquired by merger or takeover, or bought on the second-hand locomotive market. The vast majority (62) came from the Missouri Pacific Railroad, while locomotives were also acquired from the Chicago and North Western Railway (14) and Southern Pacific Railroad (9). A further 15 were acquired from the Pittsburgh and Lake Erie Railroad, being surplus to their requirements, while a further two have been leased from Helm. The Alaska Railroad had four MP15DCs used as yard switching engines, numbered 1551-1554. As of 2/28/2011 LEF&C (1551)#25 & (1552)#26, 1553, 1554 were sold to GATX, a RR leasing fleet. Two were obtained from the Lake Erie, Franklin and Clarion Railroad; the other two were obtained from the Kelley's Creek and Northwestern Railroad. Caltrain has two MP15DCs used for yard switching and work train service, numbered 503 and 504.
Former Milwaukee Road units are now owned by the Soo Line Railroad (an American operating subsidiary of the Canadian Pacific Railway); those not painted in the Canadian "Golden Beaver" scheme have worn a Soo Line patch job; those wearing it are often called "Bandits". Six former Milwaukee units returned to "home rails" in 2008, serving the growing regional Wisconsin & Southern Railroad WSOR in Milwaukee, Madison, and Horicon. In addition, Union Pacific has bought many examples on the used locomotive market. The New York & Atlantic Railway, which carries freight on Long Island, uses 4 former Long Island Railroad MP15ACs to haul freight along with other ex LIRR locomotives. Two units sold new to the DOE at Hanford, WAshington are now in operation as Tri City Railroad #16 and #15. The Knoxville and Holston River Railroad also owns a unit.
- Sarberenyi, Robert. EMD MP15DC, MP15AC, and MP15T Original Owners
- Pinkpank, Jerry A (1973). The Second Diesel Spotter’s Guide. Kalmbach Books. pp. 10, 12–13,48–50. LCCN 66-22894.
- Pinkepank, Jerry A.; Marre, Louis A. (1979). Diesel Spotters Guide Update. Kalmbach Books. pp. 4–9. ISBN 0-89024-029-9.
- Johnston, Howard; Harris, Ken (2005). Jane’s Train Recognition Guide. HarperCollins Publishing. p. 414, 425. ISBN 978-0-06-081895-1.
- Sarberenyi, Rob (2013). "UtahRails.net EMD MP15DC, MP15AC, and MP15T Original Owners =". Don Strack. Retrieved 5 August 2013.
|Wikimedia Commons has media related to EMD MP15DC locomotives.|
- Combs, John. (2006) Alaska Railroad Locomotive Roster. Retrieved on May 14, 2006
- GATX Rail Locomotive Group. MP15DC specification page. Retrieved on April 5, 2005.
- Hayden, Bob (Ed.) (1980). Model Railroader Cyclopedia-Volume 2: Diesel Locomotives. Kalmbach Books. ISBN 0-89024-547-9.
- Strack, Don. (2004) Union Pacific Railroad Locomotive Model Quantities – All-Time (1934-2002). Retrieved on April 6, 2005.