Pennsylvania Railroad class P5

The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric. Although the original intention was that they work mainly passenger trains, the success of the GG1 locomotives meant that the P5 class were mostly used on freight. A single survivor, prototype #4700, is at the National Museum of Transportation in St Louis, Missouri.

They had an AAR wheel arrangement of 2-C-2, or 2′Co2′ in the UIC classification system — three pairs of driven wheels rigidly mounted to the locomotive, with a two-axle unpowered truck at each end. This is an equivalent to a 4-6-4 in the Whyte notation. The PRR did not have any 4-6-4 steam locomotives, so the P5s were the only 4-6-4 type locomotives owned by the PRR.

The first P5s were built with box cabs. A grade crossing accident in which the crew were killed led to the substitution of a central cab to give better crash protection, a streamlined steeple type, in later production, a design which was also applied to the GG1.

When the GG1s were put in passenger service, the P5s were regeared and used in freight service for many years. The last of the class was withdrawn from service in April 1965.