System including a device for attaching an object at the rear and on the outside of a motor vehicle and device for transmitting information from the vehicle to the attachment device

The invention relates to a system comprising a fixing device (10) for attaching an object to the rear and exterior of said motor vehicle and a device for transmitting information from said motor vehicle to said fixing device (10), said fixing device (10) comprising a support platform (11) capable of being fixed to the rear structure (1) of the vehicle and comprising a substantially vertical plate (16) having, on one of its faces, a lighting system (31, 32) and a registration plate (30). The information transmission device comprises a transmitter capable of being connected to an on-board diagnostic port of the vehicle, a receiver fixed on the other face of the vertical plate (16) and capable of receiving by wireless link the lighting system activation control information (31, 32) transmitted by the transmitter.