The Class 59 locomotives were built and introduced over a ten year period from 1985 and were the first locomotives to be built in the USA and operated privately on the United Kingdom railway network on a regular basis. The first orders arose as a consequence of Foster Yeoman becoming disillusioned with the reliability of locomotives provided for their stone and aggregate haulage services by British Rail and so four locomotives were ordered from Electro-Motive Diesel by Yeoman, based on achieving a 95% reliability rate.