Passenger coach couchette coach DEV AO SNCF Ep.IV

The first family of new SNCF carriages, DEV AO (Ordinary Steel) carriages, brought a new look to passenger carriages, with access doors located in the plane of the side panels, wraparound aprons that even concealed the bellows, retractable steps and forced air heating for greater passenger comfort. The speed record of 331 km/h was set in March 1955 with a locomotive-hauled train consisting of 3 DEV AO cars. The DEV AO wagons, built in 1605 copies, were used from 1950 for long-distance trains, from which they were later replaced by the UIC Y wagons and then Corail wagons.

DEV AO wagons, without exception with compartments, come in two series: “short” DEV AO wagons and “long” DEV AO wagons, models produced by Arnold.

The development of the long DEV AO carriages was an indirect consequence of the switch to two classes in June 1956. Among the short DEV AO carriages already built, the C10 carriages became B10s while the B9c9 couchette carriages remained B9c9 carriages.

In order to keep the same capacity with 10 day compartments and compartments convertible into berths with the same comfort conditions, a new series of lengthened DEV AO passenger coaches (B10c10, then B10, A9 and A4c4B5c5) was introduced.