Since the existing B-B electric locomotives of the Midi could not reach speeds of more than 100 km/h, an express locomotive was required. As in other countries at that time, the choice fell on a locomotive with driving axles mounted in the frame and carrying axles which were movable. The design of the running gear came from the E 3100 with a 2-C-2 wheel arrangement and was extended to include an additional driving axle.