text: Order and specification After reviewing the existing privately commissioned , which was more powerful, highly reliable and with lower operating costs, EWS approached its builder Electro-Motive Diesel (EMD), then a division of General Motors. EMD offered their JT42CWR model, which had the same loading gauge-passing bodyshell as the Class 59. The engine and traction motors were different models to enable higher speeds, and the Class 66s incorporated General Motors' version of a "self-steering bogie" ("radial truck", in American usage), designed to reduce track wear and increase adhesion on curves.
  Placing what was termed as "the biggest British loco order since steam days", EWS placed an order for 250 units in May 1996 to be built at the EMD plant in London, Ontario, Canada at a cost of £375 million. Financed by Locomotion Capital (later Angel Trains), the first locomotives were ready in early 1998; the fastest delivery of an all-new locomotive type by GM.
  The EMD 710 12-cylinder diesel engine is a development of a two-stroke engine used for over 20 years, whilst the EM2000 control equipment is the same as that used on Irish Railways IE 201 Class. EWS reduced the locomotive's time into operation through specifying cab systems laid out like the Class 59, whilst increasing availability with a fuel tank of  capacity, compared to  on a standard Class 47.