Following poor reliability experience with the first generation diesel locomotives, in the 1960s a second dieselisation programme was undertaken with the introduction of sixty-four locomotives in three classes (121, 141 and 181) built by General Motors, of the United States. This programme, together with line closures, enabled CIÉ to re-eliminate steam traction in 1963, having previously done so on the CIÉ network prior to taking over its share of the Great Northern Railway. In parallel, NIR acquired three locomotives from Hunslet, of England, for Dublin-Belfast services. The Metropolitan-Vickers locomotives were re-engined by CIÉ in the early 1970s with General Motors engines.