The EMD SD40-2 is a 3,000 horsepower (2,250 kW) model of C-C diesel-electric locomotive built by General Motors' Electro-Motive Division between January 1972 and February 1986; 3,957 examples were built, and most larger North American railroads have operated the type. Part of the EMD Dash 2 line, the SD40-2 was an upgraded SD40 with modular electronic control systems, HT-C trucks, and many other detail improvements. The SD40-2 is one of the best-selling diesel locomotive models of all time. Union Pacific and Canadian Pacific operate some of the largest fleets of the type. The SD40-2 was not the most powerful locomotive type even when introduced; EMD's SD45 and SD45-2 delivered 3,600 hp (2,900 kW), as did GE Transportation Systems' U36B/C and ALCO's C636. However, the SD40-2 was significantly more reliable and economical than the higher-powered units, the latter becoming increasingly important with the oil crises of the 1970s. The British Rail Class 59 was derived from the SD40-2. Three cabless SD40-2Bs were also created from standard SD40-2s by the Burlington Northern Railroad in the early 1980s. Just as the SD38, SD40, and SD45 shared a common frame, so did the SD38-2, SD40-2, and SD45-2. It was 3 ft (0.91 m) longer than the previous models, giving an overall locomotive length of 68 ft 10 in (20.98 meters) over the coupler pulling faces. The SD38-2 and SD40-2 shared the same basic superstructure, since they both used the same 16-645E3 engine (in naturally aspirated and turbocharged form respectively); the long hood was 18 inches (0.46 m) longer than the SD38 and SD40, but since the increase in frame length was even greater, the SD38-2 and SD40-2 were left with even larger front and rear "porches" than the earlier models. These empty areas at front and rear are distinctive spotting features to identify the Dash 2 models of both units. The SD40-2 can be distinguished from the SD38-2 by having three roof-mounted radiator fans instead of two.