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The "MP15" Series (MP15DC, MP15AC, MP15T)

Last revised: December 19, 2024

By: Adam Burns

The MP15 series was Electro-Motive's immediate follow-up to the earlier SW1500 line, manufactured between 1966 - 1974. This was the first switcher EMD offered as essentially a potential road-switcher with its 1,500 horsepower and operational Blomberg trucks.

This continued with the MP15 where Blombergs became standard and was even equipped with larger fuel tank for main line freight service.  EMD also lengthened the frame and the model also featured the same electrical components as the builder's "Dash 2" line of road-switchers.

When EMD released alternating current technology in 1975; this changed the designation of the original model to MP15DC and the new variant as the MP15AC. 

In addition, the MP15T was later offered in 1984 sporting a turbocharged eight-cylinder prime mover for improved fuel economy. Overall, the series sold relatively well and many MP15's remain in service on both large and small railroads.

Photos

CSX MP15AC #1170 leads westbound autorack train Q219 over Sand Patch on August 28, 1993. Wade Massie photo.

History and Background

Throughout the history of Electro-Motive's switcher line the builder saw successful sales, more than could be said for its road-switchers after the 1980s.  

From the earliest SC and NW models to the final series presented here, the manufacturer produced thousands of switchers, many of which remain on Class I rosters for light-duty service.  

The MP15 (later redesignated as the MP15DC) was the first in the series and interestingly, was meant to not only for yard, industrial, and light branch duties but also as a general road switcher. It replaced the earlier SW1500, featuring a larger fuel tank (1,400 gallons) and Blomberg trucks as standard for general road service.

Interestingly, EMD actually considered the MP15 a true road-switcher rather than a switcher. While it carried the look of the latter, internally it was indeed a small road switcher, essentially a GP7.

With the introduction of the MP15AC in August, 1975, EMD made a number of updates to the locomotive.  As Bob Hayden notes in his book, "Diesel Locomotives: Cyclopedia, Volume 2," it was 18 inches longer than the MP15DC which allowed for a larger fuel tank (1,600 gallons). 

A recently delivered Missouri Pacific MP15DC, #1536, in the fall of 1974. American-Rails.com collection.

In addition, EMD moved the radiator air-intakes to the lower side of the hood on the locomotive's pilot end.  As Louis Marre points out in his book, "The Contemporary Diesel Spotters Guide: A Comprehensive Reference Manual To Locomotives Since 1972," this design was actually based from EMD's successful SD40T-2 and SD45T-2, the so-called "Tunnel Motors."

These powerful road-switchers were almost entirely purchased by Southern Pacific (along with the Rio Grande) and featured air intakes low on the frame to grab fresh air as through the many tunnels and snowsheds on Donner Pass.

Marre goes on to note the MP15 series was marketed to railroads as a combination switcher/light road-switcher to replace aging GP7s and GP9s.  Interestingly, its lack of a toilet ultimately hindered sales as some state laws required this feature on locomotives used as either lead units or in MU sets outside of yard work. 

In addition, the MP15AC was more expensive than its earlier counterpart (MP15DC), further hurting sales.  Nevertheless, it did sell relatively well. The MP15AC accomplished its use of "AC" power by using an alternator, which then converted the power back to DC, through the use of a silicon rectifier.

Data Sheet and Specifications

Production Rosters

MP15DC

Total Built = 339

MP15AC

Total Built = 217

MP15T

Total Built = 43

Export Production Roster

MP15DC

Total Built = 12

MP15AC

Total Built = 25

Milwaukee Road MP15AC #435 leads a short freight eastbound near Brodhead, Wisconsin on May 31, 1978. Richard Kundert photo. American-Rails.com collection.

The MP15T was essentially a variant of the MP15AC in that it featured a turbocharged prime mover, which was meant to be more fuel efficient (it was also slightly longer than the MP15AC at 50' 2") using only an eight-cylinder version of EMD's 645E prime mover. 

The model was built between October, 1984 and November, 1987. Few MP15Ts were ever built, as all but one were manufactured for the Seaboard System, which purchased 42 units.

Sources

• Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.

• Hayden, Bob. Diesel Locomotives: Cyclopedia, Volume 2 (Model Railroader). Milwaukee: Kalmbach Publishing Company, 1980.

• McDonnell, Greg. Locomotives: The Modern Diesel & Electric Reference, 2nd Edition. Buffalo: Boston Mills Press/Firefly Books, 2015.
  

• Marre, Louis A. and Pinkepank, Jerry A. Contemporary Diesel Spotter's Guide, The: A Comprehensive Reference Manual To Locomotives Since 1972.  Milwaukee: Kalmbach Publishing Company, 1989.

• Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.