The Eurotunnel Class 9 or Class 9000 are six-axle high-power Bo′Bo′Bo′ single-ended electric locomotives built by the Euroshuttle Locomotive Consortium (ESCL) of Brush Traction and ABB. The class was designed for and is used exclusively to haul the Le Shuttle road vehicle services through the Channel Tunnel. Background and design Tendering for the locomotive procurement began in 1989. The specification included; a top speed of ; a terminal-to-terminal travel time of 33 minutes pulling a train; an axle load limit of ; an operating temperature range between and ; a loading gauge within the UIC 505-1 standard; a minimum curve radius of ; be able to start a shuttle train on a 1 in 160 (0.625 %) gradient with one locomotive bogie inoperative (at ), and a single locomotive should be able to start the train on the same gradient if the other locomotive failed. The operating concession agreement between Transmanche Link/Eurotunnel and the British and French governments required that there be a locomotive on either end of the train, allowing splitting and reversing of the train. The design specifications implied a minimum power of , and also meant that a four-axle design would not be guaranteed to be able to supply sufficient tractive effort. The French railway lobby was suggesting using three four-axle Bo′Bo′ locomotives (such as the SNCF BB 26000). ESCL proposed a six-axle Bo′Bo′Bo′ locomotive derived from the narrow-gauge EF class locomotives supplied by Brush Traction to the New Zealand Railways Corporation and won the contract with an initial order of 40 in July 1989. The main traction electrical system consists of: two pantographs (duplicated for redundancy) collecting a 25 kV AC supply which feeds the main transformer, with separate output windings rectified to a DC link (one per bogie) using four quadrant converters. The direct current drives a three-phase inverter, which powers two asynchronous three-phase induction motors. There are two additional output windings on the transformer for the locomotive's auxiliaries and to supply power to the train vehicles. The bogies were a fabricated steel design, with coil spring primary suspension. The traction motors and gearboxes (one per axle) were mounted to the bogie frame and connected to the wheels by a flexibly coupled quill drive. Traction links were connected to the bogie frame at a height of above rail. The locomotive superstructure is supported on coil springs on a central swing bolster, and the centre bogie