A vehicle is disclosed having a chassis supporting a platform having a network of criss-cross guiding rails. Trolleys circulate along these rails so as to be selectively movable towards the rear of the vehicle for the loading and unloading of road signs. The trolleys are provided with a braking device to enable them to be immobilized on the rails. The vehicle may be a trailer for the transportation of road signs, for example to indicate road works on streets and expressways.