ALCO Century 855

The ALCO Century 855 was a diesel-electric locomotive of 5,500 horsepower that the American Locomotive Company built in 1964 for the Union Pacific. It was Alco's most powerful diesel-electric locomotive and, at the time, the most powerful diesel locomotive ever built, until the EMD DDA40X surpassed it in 1969. Two cab units and one booster unit were built, each powered by a pair of 16-cylinder ALCO 251C engines and carried on four two-axle trucks in a B+B-B+B arrangement. Union Pacific wanted very high power to replace its turbine locomotives on the Overland Route, but mechanical unreliability, overheating and electrical fires ended their use and all three were scrapped by early 1972.