Locomotive 10 may include a plurality of such systems and subsystems such as an air and air brake subsystem 12, an auxiliary alternator subsystem 14, a battery and cranker subsystem 16, a cab signal subsystem 18, an engine cooling subsystem 20, an equipment ventilation subsystem 22, a propulsion subsystem 24, a traction alternator subsystem 26, a locomotive control system 28 and an on-board diagno