Bio Edit

The EMD (Electro Motive Division) GP50 is a type of four-axle, 16-cylinder, 3,500hp to 3,600hp diesel locomotive built from 1980 to 1985 with 278 built.
BN GP50-2

A BN "Tiger Stripe" GP50 leading a typical 1980's consist.

The GP50 was one of the very first full production diesel locomotives built by EMD to include revolutionary microprocessor controls which have been equipped with every main production diesel-electric locomotive built by the company beginning with the preceding GP40X. The model is essentially the four-axle version of the SD50.

Chicago And North Western (CNW), Missouri Pacific (MP; Mopac), St. Louis-San Francisco (SLSF; Frisco), Burlington Northern (BN), Santa Fe (ATSF) and Southern (SOU) were among the only customers to order the model.

Many are currently used in yard and local service, though some have since been scrapped or rebuilt.

BNSF, NS, and UP are the main current owners and operators, while regional and/or shortline companies (with the exception of some leasing companies) such as the Indiana And Ohio Railway (IORY) operate fleets of ex-BN units for primary use (albeit de-rated to 3,000hp and under). Others such as the Fort Worth And Western (FWWR) own and operate a handful of ex-UP units from Mopac and CNW heritage.

Between 2004-2007, NS rebuilt most of their GP50 units to GP38-2 specs, dubbing them "GP38-3's" (NS #5801-5837). Recently, NS has since rebuilt the remainder of their existing GP50 units into Tier 3-compliant GP33ECO units (NS #4700-4724) built to 710 specs (having a 12N-710G3B-T3 rated at 3,000hp), and were built exclusively for services in and around the Atlanta, GA and Chicago, IL areas (some have since been found elsewhere). As of 2015, none of the original GP50 units remain on their roster.


The GP50 was the very first commercially successful, mass-produced model of four-axle diesel locomotive built by EMD to include revolutionary, high-tech, state of the art microprocessor control systems which replaced the more traditional electronic wiring modules; and was originally meant to serve as a replacement to the ever-successful GP40-2, which was one of the last traditional four-axle models built by the company. Greenlit by the initial success of the preceding GP40X testbeds, the model was first demonstrated to western-based carriers such as the Chicago And Northwestern (CNW), whom were among the first to order a total of 50 units (CNW 5050-5099) to be used in heavy haul applications for heavy coal drag service between Wyoming and Illinois from within the Powder River Basin, 

BNSF GP50L units

A duo of BN (now BNSF) GP50L units awaiting their next assignment.

but were eventually reassigned as heavy duty yard switchers for switching and/or sorting long strings of freight cars within the large facilities of Chicagoland region once they began receiving their first delivery of new SD60 units shortly after the 50 Series discontinuation in 1985.

Eventually, the Missouri Pacific (MP; Mopac) grew interested in ordering a fleet of 30 units prior to the 1982 merger with Union Pacific (UP), while Frisco (SLSF) placed an order for 9 units; yet the order was fulfilled during the finalization of the BN merger in 1980. Later on, however, BN placed an order for an additional 63 units in the years following the demise of Frisco. ATSF on the other-hand, purchased a quantity of 45 units between 1981 to 1982 for use on their high-speed intermodal trains, but were eventually reassigned to yard service and were configured in a "master-slave" fashion for hump service. Meanwhile, only one eastern carrier, Southern (SOU), placed an order for the largest amount massing a total of 90 units in September 1980, and were built in the traditional "hi-hood" fashion for long hood forward applications like their predecessors.


Although it was the first commercially successful microprocessor-equipped four-axle model built by EMD, the GP50 suffered a number of flaws and commercial failures as with its six-axle counter-part: the SD50. Because of the early-1980's recession and subsequent company mergers (resulting in traffic slumps), there was a severe lack of interest and popularity from most railroads that originally demonstrated the GP40X testbeds and subsequent GP50 demonstrators. Many performance defects plagued the model as with its six-axle counter-part, which further prevented any orders generated by railroads. Rather, many of the host railroads which originally sought interest in the model (such as Southern Pacific) preferred placing orders on the more successful GP40-2, which lasted far longer in production and was furthermore garnered with high popularity over its so-called "successor". Furthermore, the GP50 often received the same amount of negative criticism as the SD45, GP35, and SD50 (most rail enthusiasts often refer to the "5" in an EMD diesel locomotive model or series as being part of the "unlucky 5"; meaning that the number led to "bad luck"). Hence, the model experienced the same amount of technical difficulties and/or performance issues regarding the wiring, electronics, prime-mover (the flawed 16-645F3), traction motors, brakes, cooling systems, and so forth. Though, the troubleshooting of said problems made each and every model more successful afterward compared to its initial debut.

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A wrecked CNW GP50 revealing its innards.

Despite not gaining a high amount of popularity or success like what EMD originally hoped for, the model was still well-received by owners once the initial improvements were made. Though, despite these improvements, the model still garnered a lack of attention amongst railroads, for GE was slowly building up their ever-increasing momentum as the leading locomotive builder with their new Dash 8 line, which furthermore resulted in EMD losing their title. Fortunately enough, the GP50 also served as a transitional model: one of the last domestic models built with a 645 series engine, and one of the first to be equipped with microprocessor technology (besides the GP40X); but also one of the models which spelled the end of EMD's market dominance as the "number one locomotive builder". 

In spite of the GP50's lack of commercial recognition, the succeeding GP60 gave the four-axle "General Purpose" line a last breath of hope in the diesel locomotive market. Although sales weren't nearly as great compared to previous models, the GP60 marked an end for a long and varied chapter of EMD's history and served as a drastic improvement over the GP50. 


The last five units delivered to the BN (3158-3162) were built with specialized cabs (known as a "GP50L"; "L" for "lengthened" or "long"), consisted of five seats, and were given cabs lengthened to 23" meant to house large crews during the railroad's transition of phasing-out the once-present and popular caboose in favor of utilizing FRED's and having brakemen assigned to local and yard services as opposed to being employed on mainline trains which once required the need of a caboose and crew. Said units and methods are reminiscent of CSX's (SCL's) BQ23-7 fleet, considering that both specialty models were built for said exact purpose: acting as a caboose and/or accommodating large crews.

Spotting DifferencesEdit

Although similar, the GP50 shouldn't be confused between the GP40-2 and subsequent GP40.

  • Many GP50 units are fitted with the distinct "free-flow" style (or "Phase 2") blower duct; though many later production GP40-2 and GP38-2 units received the same style duct (notably with CP, FEC, and DRGW).
  • Larger radiator fans.
  • Taller wheelbase.
  • Larger air intakes (or radiators).
  • Several were built with radiator fan or weather covers (notably the CNW units).
  • Larger, more distinct exhaust vent.
  • Shorter or smaller dynamic brake grid.
  • Larger fuel tanks.


Model GP40X GP50
Production Dates 1977-1978 1980-1985
Total Built 23 278
Length 60' 2" 60' 2"
Wheel Arrangement B-B B-B
Engine 16-645F3 16-645F3B
Horsepower 3,500 3,500 (3,600)
Alternator AR10X2-D14 AR15-D18
Traction Motors D87X D87
Weight x 1,000lbs. 274-278 260-277

Production RosterEdit

Owner Quantity Road Numbers Notes
Atchison, Topeka, And Santa Fe (ATSF; Santa Fe) 45 3810-3854 All in service with BNSF. Some rebuild and de-rated to 2,500hp (re-classed as a "GP25" or a "GP25-2").
Burlington Northern (BN) 63 3100-3162 Most in service with BNSF; many retired, several scrapped or rebuilt.
Chicago And Northwestern (CNW) 50 5050-5099 Most in service with Union Pacific (UP), many retired, sold, or scrapped.
Missouri Pacific (MP; Mopac) 30 3500-3529 To UP. Most still in service; several rebuilt or scrapped.
St. Louis-San Francisco Railway (SLSF; Frisco) 9 790-799 All went to service with BN, and were delivered shortly after the merger in 1980. #3100 (SLSF #791) was delivered in Frisco paint, but with BN patchwork. The rest of the units 3101-3109 (SLSF #790 and #792-799) were delivered in BN paint. Various dispositions. 
Southern Railroad (SOU) 90 7003-7092 Rebuilt to GP38-3 and GP33ECO. Many scrapped, retired, or auctioned off to leasing and/or shortline companies.


During the time of the model's production, the SLSF (St. Louis-San Francisco; or "Frisco") was in the process of undergoing a merger with the BN in 1980, while Missouri Pacific (MP; "Mopac") was undergoing acquisition into becoming a subsidiary under Union Pacific (UP) in early 1982. Therefore, certain units were delivered in each of the latter's paintschemes, but were instead given new numbers to fit on the holding companies rosters.

Such example would be BN #3100 (SLSF #791), which was the only GP50 unit delivered in Frisco livery, but received its initial BN numbering and letter stenciling to signify its new ownership.

UP on the other-hand, simply followed their rival SP's tradition with their SSW subsidiary by painting the holding company's livery over their newly acquired units, but with "Missouri Pacific" in place of "Union Pacific" within the UP's "Armor Yellow" livery.

12 UP GP50 units were rebuilt by MPI (MotivePower Industries) in 2007 and are classified as an MP20GP. Said units are powered with CAT 3612 engines (supplied from EMD's current owner; Caterpillar Inc.) and were built to be Tier 2-compliant under the US EPA's juristiction.

Several ex-UP GP50 units were scrapped and had their engines retrofitted with Utah Railway's fleet of MK5000C units.

BN #3111 (pictured above) was one of the several units painted in the road's short-lived "Tiger Stripe" safety scheme meant to spread awareness for railroad crossing safety by making lead units on trains from within a consist more visible. The scheme eventually proved to be unnecessary.

Two UP units (UPY #939 and UPY #940) have since been rebuilt into S1-6B road slugs, and are the only other road slugs on both the company's yard and main road roster.

Like many diesels owned by the Mopac, their GP50 units weren't equipped with dynamic brakes, therefore making the Mopac GP50's the only units to not be equipped with such feature.

Sevral BNSF units were de-rated and reclassed as a "GP25" or a "GP25-2" sometime between 2006-2010, and are de-rated from 3,500hp to 2,500hp. As of early 2017, however, one unit (BNSF #3154) has been retrofitted with a unique cab upgrade (known as a "Thomas Brow") to house air conditioning units and Positive Train Control (PTC) equipment for intercity yard operations. To date, SD40-2 #1689, GP40M #3006, and numerous other units have received said upgrade. 


Sources Edit (BNSF #3154) 

Trains Magazine Vol. 77, Issue 6, Pg. 13