We met some 10 years when it published the first part of the "Diesel Locomotives", dedicated to the first generation of this type of traction. Renfe valued acquire diesel locomotives among several options presented by domestic manufacturers in collaboration with European and American manufacturers. The most favourable option, influenced by the international strategic context of the time, was the builders of Americans. The locomotives of the company ALCO, the standard models "World DL-500" were the ones that started the dieselisation of trains forming the series Renfe 1,600 and 1800, widely covered in Volume I of this work. Years later, because of indecisions and, above all, lack of funding, the series was extended through an international competition in which the order was divided between Alco and General Motors (Volumes II and III). ALCO locomotive was the same type DL-500 but adapted and improved with two symmetrical booths, leaving the cabin at one end aerodynamics of the original model.
The new series, called the 2,100 allowed decommisioning steam trains throughout Andalusia and Galicia, in addition to extending other locomotives in the series amplas areas in Extremadura and Castile.
The ALCO locomotives and their heirs of MLW and after Bombardier offered ranges export to the world that, without reaching the shares of major competitors, GE and GM-EMD, manufacture under licence enabled wide dissemination in many networks.
This closes a cycle that began in the mid-fifties with the arrival of the locomotive to Renfe prototype ALCO, DL-500 and closes with locomotives DL-500S bicabinas, Series 2100 Renfe, and locomotives MLW / export Bombardier, both of Portugal as the built in partnership by CAF for Brazil.
The robustness of these locomotives have allowed to continue in active service due remodeled until today, albeit precariously in maintenance work on roads Renfe and some private contractors. A special mention to the presence of two dozen locomotives on the railways in Argentina, acquired second-hand in the mid-nineties.