support on a cowl unit is provided by the frame of the locomotive, rather than in the body as with a cab unit. This allows manufacturers to cheaply and easily create full-width locomotives from their hood unit designs by simply adding cowling. Cowl units were first introduced as a special order from the Santa Fe, which wanted a sleeker design for its passenger equipped hood units. Although the first cowl units (such as the EMD FP45 and the GE U30CG) were meant for passenger service, EMD would later offer freight-only derivatives starting with the F45. Great Britain Cab units were not generally used in Great Britain. The traditional makers continued to use heavyweight frames and cowl units instead. The LMS twins 10000 and 10001 used the design and later locomotive types such as the British Rail Class 37, and British Rail Class 40 utilised cab units but the term "cab unit" is not used in Britain. The Class 37 and Class 40, like most British diesel and electric locomotives, has a cab at each end. As locomotives with a cab at each end do not have a "front" and "rear" end, the British convention is to refer to "no.1 end" or "no.2 end". No.1 end is always the end of the locomotive containing the cooler group and is usually identifiable from the exterior by large cooling grilles for the radiators. References Diesel locomotives