Fall-proof system for a motor-vehicle transporter comprising: at least one parapet structure connected to at least one longitudinal support, an articulated spacing kinematic mechanism, said at least one longitudinal support being able to be connected in an articulated way to an edge of a loading surface of the vehicle by means of said articulated spacing kinematic mechanism, and a platform connected in a rotating way to a longitudinal support able to be connected in an articulated way to the edge of said loading surface to rotate around an axis parallel to the longitudinal support and to the edge so as to cover the empty space created when the parapet structure moves away from the loading surface, said articulated spacing mechanism being configured to allow a movement of the parapet structure with respect to the loading surface between a first operating position in which the parapet structure is substantially adherent to said loading surface and a second operating position in which the parapet structure is spaced from the loading surface to facilitate the loading and unloading operations of the vehicles from said loading surface, characterized in that the platform comprises at least one section comprising inclined surfaces which are in contact with an abutment element able to be fixed to the loading surface, said inclined surfaces being configured to bring the platform from the second operating position, aligned to the loading surface, to the first operating position substantially perpendicular to the loading surface, following the displacement of the longitudinal support of the structure parapet from the second operating position spaced from the loading surface to the first operating position substantially adhering to the loading surface. at least one parapet structure connected to at least one longitudinal support, an articulated spacing kinematic mechanism, said at least one longitudinal support being able to be connected in an articulated way to an edge of a loading surface of the vehicle by means of said articulated spacing kinematic mechanism, and a platform connected in a rotating way to a longitudinal support able to be connected in an articulated way to the edge of said loading surface to rotate around an axis parallel to the longitudinal support and to the edge so as to cover the empty space created when the parapet structure moves away from the loading surface, said articulated spacing mechanism being configured to allow a movement of the parapet structure with respect to the loading surface between a first operating position in which the parapet structure is substantially adherent to said loading surface and a second operating position in which the parapet structure is spaced from the loading surface to facilitate the loading and unloading operations of the vehicles from said loading surface, characterized in that the platform comprises at least one section comprising inclined surfaces which are in contact with an abutment element able to be fixed to the loading surface, said inclined surfaces being configured to bring the platform from the second operating position, aligned to the loading surface, to the first operating position substantially perpendicular to the loading surface, following the displacement of the longitudinal support of the structure parapet from the second operating position spaced from the loading surface to the first operating position substantially adhering to the loading surface.