EMD GP15 (-1/T/AC)
Union Pacific Yard (UPY) 742, a GP15-1 idles in Union Pacific's Global 1 intermodal yard in Chicago, IL.
Type and origin Power type Diesel-electric Builder General Motors Electro-Motive Division (EMD) Model GP15-1 GP15T GP15AC Build date June 1976 – March 1982 (-1) October 1982 – April 1983 (T) November & December 1982 (AC) Total produced 310 (-1) 28 (T) 34 (AC)
Specifications Configuration: ​  • AAR B-B Gauge 4 ft 8+1⁄2 in (1,435 mm) standard gauge Driver dia. 40 in (1,016 mm) Minimum curve 120 ft (36.6 m) Length: ​  • Over couplers 54 ft 11 in (16.74 m) Width 10 ft 3+1⁄8 in (3.127 m) (over hand rail supports) Height 15 ft 2+1⁄2 in (4.636 m) Loco weight 246,000 lb (111,600 kg) (-1) 244,000 lb (110,677 kg) (T) Fuel capacity 2,400 imp gal (11,000 L; 2,900 US gal) Lubricant cap. 135 US gal (511 L; 112 imp gal) Coolant cap. 210 US gal (795 L; 175 imp gal) Sandbox cap. 56 cu ft (1.59 m3) (basic) 72 cu ft (2.04 m3) (special) Prime mover EMD 12-645E (-1/AC) EMD 8-645E3C (T) RPM: ​  • RPM low idle 235  • RPM idle 300  • Maximum RPM 904 Engine type V12 2-stroke diesel (-1/AC) V8 2-stroke diesel (T) Aspiration Roots blower (-1/AC) Turbocharger (T) Displacement 7,740 cu in (126.8 L) (-1/AC) Alternator AR10 (AC) Generator AR10-D14 (-1/T) Traction motors 4×D77 (-1/T) ​  • Continuous 920 Amperes (with 62:15 gearing) (-1/T) Cylinders 12 (-1/AC) 8 (T) Cylinder size 9.1 in × 10 in (231 mm × 254 mm) (-1/AC) Transmission diesel electric Loco brake Straight air Train brakes Westinghouse 26L air brake
Performance figures Maximum speed 53 mph (85 km/h) (with 65:12 gearing) 70 mph (110 km/h) (with 62:15 gearing) 76 mph (122 km/h) (with 61:16 gearing) 82 mph (132 km/h) (with 60:17 gearing) Power output 1,500 hp (1.12 MW) Tractive effort 47,000 lbf (210 kN)
Career Locale United States

The EMD GP15 is a 4-axle diesel-electric locomotive built by General Motors Electro-Motive Division between June 1976 and April 1983. Intended to provide an alternative to the rebuilding programs that many railroads were applying to their early road switchers, it is generally employed as a yard switcher or light road switcher. There were 3 variants made: the GP15-1, the GP15T, and the GP15AC. The GP15-1 and GP15AC are powered by a 12-cylinder EMD 645E engine, which generates 1,500 hp (1,119 kW). The GP15T differs in that it uses a turbo charged 8-cylinder instead of the roots blown 12-cylinder to generate the same horsepower. The GP15AC differs from the others as it uses an AC alternator connected to the engine instead of a DC generator to drive the traction motors. The radiator section is similar to those found on the EMD SD40T-2 and EMD SD45T-2 "tunnel motors," leading some observers to incorrectly identify the units as such or as GP15Ts, and giving them the nickname "baby tunnel motors".^[1] A number of GP15-1s remain in service today for yard work and light road duty.

The GP15-1 was the most popular variant as it did not contain either of the newer technologies of the other two variants (turbocharging or AC control). EMD built a total of 310 units for American railroads in this variant between June 1976 and March 1982.

The Missouri Pacific Railroad purchased more units than the other three buyers combined. For spotting purposes, the MP models have a number of visually distinguishing features, though not all were applied consistently to the MP units:

• The MP units have a grab iron ladder mounted on both sides of the long hood end;
• MP's initial order of GP15-1s rode on Blomberg M trucks rather than the more common Blomberg B (all subsequent units were delivered with Blomberg B trucks) — and, while the standard Blomberg B truck carries two brake shoes per wheel, many MP units were equipped with only a single brake shoe per wheel;
• #1555–#1574 were outfitted with the standard 81" nose, while the remaining units (all built in December 1976 or later) came with an 88" nose;

EMD built 28 examples of a variant, the GP15T, between October 1982 and April 1983. It was a very close cousin to the GP15-1, but used a turbocharger in order to generate more power from a smaller engine. Power was provided by an 8-cylinder diesel engine that generated 1,500 hp (1.12 MW), the same as the GP15-1, but with four fewer cylinders.^[1]

28 examples of this locomotive model were built for American railroads. The Chessie System received the majority of them as C&O 1500–1524 (25 units),^[3] while the rest went to the Apalachicola Northern Railroad in Florida as AN 720–722 (3 units).^[2]

The GP15AC is a variant built between November and December 1982. This model differs from the GP15-1 due to Missouri Pacific specifying new AR10 AC alternators instead of rebuilt D32 DC generators. The only external difference between the GP15AC and the GP15-1 is a straight side sill (shared with the EMD GP15T) not related to the transmission difference.

34 examples of this locomotive model were built in total: 30 for Missouri Pacific Railroad, and four for Venezuela's IFE.^[2]

Union Pacific has rebuilt 22 of their GP15-1's into GP15N's at their Jenk's shop. These units received a microprocessor control system to increase adhesion, control options, and extend the life of the locomotive.^[4]

In 2021, CSX donated GP15T #1507 (built 1982 as C&O #1507) to the B&O Railroad Museum in Baltimore, Maryland.^[5] It is the first GP15 class locomotive to be preserved.

• "GP15-1 specification page". GATX Rail Locomotive Group. Archived from the original on April 8, 2005. Retrieved June 25, 2005.
• "The History of EMD Diesel Engines". Pacific Southwest Railway Museum. Archived from the original on July 22, 2014. Retrieved December 14, 2005.
• Marre, Louis A. & Pinkepank, Jerry A. (1989). The Contemporary Diesel Spotter's Guide. Waukesha, WI: Kalmbach Books. ISBN 0-89024-088-4. LCCN 88083625. OCLC 19959644.

• Sperandeo, Andy. "The EMD GP15-1: EMD's down-sized road switcher." Model Railroader, January 1990, 110–115.

• EMD GP15T Operator's Manual
• Sarberenyi, Robert. EMD GP15-1, GP15AC, and GP15T Original Owners