The GP15D is a four-axle B-Bswitcher built by MotivePower Industries and Electro-Motive Diesel. It is supplied with a Caterpillar 3512 (called a 12-170B15-T2 by EMD)V12 prime mover which develops a total power output of 1,500 horsepower (1,120 kW). 10 units were manufactured by EMD during June 2000. Another 10 units were manufactured for Amtrak by MPI during 2004. The GP15D is a hood unit with lowered long and short hoods based on MotivePower Industries' earlier MP1500D locomotives. The changes between the MP1500D and the GP15D are primarily in the control electronics, making them easier to use than the older model.
Although the GP15D is marketed as a switcher, it has a top speed of 70 mph (113 km/h), making it suitable for road switcher duties as well. The GP15D is also similar in appearance to the contemporaneous GP20D, except that the 10 GP15D units produced to date do not have dynamic brakes.