Element for vehicle double bottom, double bottom with such element, and vehicle with such a double bottom

The unit has an upper side constituting a part of floor of an interior cab of a vehicle. A lower side extends above the floor of a body shell of the vehicle. One rigidifying rib projects from the lower side and forms a duct (43) for passage of electric cables or fluid such as air for ventilation, or a fixing support. The ribs provide predetermined mechanical resistance characteristics to the unit. An independent claim is also included for a motor vehicle.