The EMD SD50 is a 3,500-horsepower diesel-electric locomotive built by General Motors Electro-Motive Division. It was introduced in May 1981 as part of EMD's "50 Series"; production ceased in January 1986. The SD50 was a transitional model between EMD's Dash 2 series which was produced throughout the 1970s and the microprocessor-equipped SD60 and SD70 locomotives. A total of 431 were built.

The SD60 is essentially identical to the SD50 externally, but has a different prime mover, the new 16-cylinder EMD 710G3A, and a computer-controlled electrical system. Chicago & North Western's railroad manual estimated that the SD60 is 3% more fuel efficient than one SD50, while a pair of SD60s was up to 16% more efficient than three SD40s pulling a standard coal train.

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