BN GP50 3122 at Clyde Yard, Chicago in its short lived experimental "tiger stripe" paint scheme in 1987.

At first glance I thought it was Tex-Mex!

(Gary Todd from Xinzheng, China, CC0, via Wikimedia Commons)



An EMD GP50 is a 4-axle diesel-electric locomotive built by General Motors Electro-Motive Division (EMD). It is powered by a 16-cylinder EMD 645F3B diesel engine, which can produce between 3,500 and 3,600 hp (2,610 and 2,685 kW). 278 examples of this locomotive were built by EMD between 1980 and 1985. BN 3110-3162 were all delivered with five cab seats, the final five of these having the cab lengthened 23 in (584 mm) vs. the standard EMD cab. The GP50 retains the same overall length of 59 feet 2 inches (18.03 meters) as the GP38, GP39, and GP40 series locomotives.


Santa Fe EMD GP50 at Corwith Yard, Chicago Area, 1987.

(Gary Todd from Xinzheng, China, CC0, via Wikimedia Commons)



EMD delivered the first GP50s to Chicago Northwestern in the summer of 1980. Much of the GP50's new technology was tested and developed with the experimental GP40X.

Changes to the 645F3B engine compared to older versions, include a stronger crankcase, new turbocharger, new plate crab for clamping the power assemblies to the crankshaft, a camshaft of increased hardness, one-half-inch-diameter plunger injectors, laser-hardened cylinder liners, rocking piston pins, and a slower idle speed. A new traction motor, the D87, has a continuous rating of 1170 amps, compared to 1150 amps for its predecessor, the D77, with new interpole and main field coils that use 16% more copper, the number of turns increased from 14 to 17 to improve commutation at high currents, longer brush life, and sturdier gearing with increased surface hardness. The new motors are connected in permanent parallel to a new AR15 alternator rated at 4,680 amps.

The GP50 was the first production locomotive to feature EMD's Super Series wheelslip control system, first seen on the GP40X. Super Series employs a Doppler radar unit mounted under the front coupler pocket to measure the locomotive's speed and adjusts the power to each axle to provide maximum adhesion while eliminating wheelslip. This system provided an increase in adhesion of at least 33% compared to conventional locomotives.

Other changes compared to the GP40-2 include an underframe with a lighter, deeper sill that reduced the frame's weight and a new exhaust system and "Q-type" cooling fans to meet January 1980 Federal noise regulations.

The GP50 was the first production locomotive series to be fitted with a microprocessor, and EMD fitted the 60 series with microprocessors as standard following the success of LARS which was developed in partnership with Burlington Northern and Rockwell Collins.


Missouri Pacific No. 3528, a GP50 at Villa Grove, IL, 1985.

(Gary Todd from Xinzheng, China, CC0, via Wikimedia Commons)


Original Owners

Railroad Quantity Road numbers Notes
Atchison, Topeka and Santa Fe Railway 45 3810-3854 All now in service with BNSF Railway.3853 wrecked and retired.
Burlington Northern Railroad 63 3100-3162 3100-3109 were ordered by St. Louis – San Francisco Railway, but delivered to BN. 3100 was the only one that received Frisco colors, though with BN number. LARS was installed on 3108-3157. Most are now in service with BNSF Railway and some are being rebuilt as GP25s.
Chicago and North Western Railway 50 5050-5099 To Union Pacific Railroad; since retired.
Missouri Pacific Railroad 30 3500-3529 To Union Pacific Railroad.
Totals 278


Norfolk Southern

In 2015–2016 the Norfolk Southern Railway rebuilt 28 of their GP50s into the low-emission GP33ECO. And in early 2016, Norfolk Southern rebuilt one GP50 into their first GP59ECO. These units, most of which utilized GP59 cores, have similar specifications as the earlier GP33ECO program but have been built without public funding contributing to their construction.


NS Train G74 with RP-M4C leading and GP33ECO 4722 trailing. 4722 is formerly SOU GP50 7048.

(Michael Hoskins, CC BY 2.0 <>, via Wikimedia Commons)


Burlington Northern Santa Fe

Around 2006 BNSF started rebuilding and derating GP50s and reclassifying them as GP25s. These locomotives are re-governed to 2500 hp and have D78 traction motors in place of the original D87s. This likely means that the Super Series wheelslip control system has also been removed since the D78 traction motor does not support it.


Chicago & North Western No. 5059, a GP50 at Blue Island Yard, Chicago area, 1987.

(Gary Todd from Xinzheng, China, CC0, via Wikimedia Commons)



Type and origin
Power type: Diesel-electric
Builder: General Motors Electro-Motive Division (EMD)
Model: GP50
Build date: 1980 – 1985
Total produced: 278
Configuration: AAR B-B
Gauge: 4 ft 8+1⁄2 in (1,435 mm) standard gauge
Wheel diameter: 40 in (1,000 mm)
Wheelbase: 43 ft 9 in (13.34 m)
Length: 59 ft 2 in (18.03 m)
Width: 10 ft 4 in (3.15 m)
Height: 15 ft 7 in (4.75 m)
Locomotive weight: 250,000 lb (113,398 kg)
Prime mover: EMD 16-645F3B
Engine type: V16 diesel
Cylinders: 16
Performance figures
Maximum speed: 65 mph (105 km/h)
Power output: 3,500–3,600 hp (2,610–2,685 kW)
Tractive effort: 65,000 lb (29,000 kg)


Missouri Pacific EMD GP50 3529 at Neff Yard, Kansas City, Missouri, March, 1989. Photographer: Craig Garver.

(Craig Garver, Public domain,


Missouri Pacific - Union Pacific

Missouri Pacific bought 30 EMD GP50's, 3500-3529. This was the final unit, built in January, 1981, as part of a small order for four units, MP 3527-3529. It was repainted UP yellow with Missouri Pacific lettering on November 14, 1984. It is shown here just five years later, well worn. All thirty of the GP50's were repainted, the only class of ex-MP units were every member was repainted yellow.

In December, 1985, this class was renumbered UP 50-79, but only twelve units were physically renumbered, and this unit was not among them. The class was once again renumbered to UP 960-989, and this unit was renumbered UP 989 on December 3, 1991.

It was renumbered once again as UP 5587 on December 31, 1991, then yet again to UP 1687 on December 30, 2003. It was slated to be rebuilt by Motive Power Industries but there is no record at that that occurred. - by Craig Garver