Abstract: In a road-transportable trailer having a connecting arm (11) of a "swan neck" type, and including an oblique arm (15), followed by a branch (17), a forward extremity of the former including a lower support rack (16), and a retractable telescopic support arm (24) disposed therein, and further including a plurality of access ramps (7, 8), the improvement relates to the facts that the branch (17) of the connecting arm (11) is foldable, is structured on an upper surface thereof as a projecting support member (20), and is adapted to be made rigid with the upper deck (35) of a forward bogie (27). A pivoting mechanism is provided which may be locked into a normally horizontal position, and is adapted so as to be in a position of alignment with an upper deck of a rear bogie (28).