The Class 59 locomotives were built & introduced over a ten year period from 1985 & were the first locomotives to be built in the USA & 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 & aggregate haulage services by British Rail & so four locomotives were ordered from Electro-Motive Diesel by Yeoman based on achieving a 95 reliability rate