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.