Road guardrail with motorcyclist-protection barrier; wherein said road guardrail comprises: - a plurality of vertical posts fixed to the ground on the side of a carriageway, and - multiple consecutive ribbon-like corrugated metal panels supported in horizontal position by said plurality of vertical posts; and said motorcyclist-protection barrier comprises: - a bracket comprising an upper portion, and a lower portion that is inclined by an angle (α1) relative to the perpendicular and acts as a shelf; said lower portion of the bracket being elastically flexible and spaced from said post; said lower portion being provided with one or more slots (23a, 23b); - two ribbon-like corrugated panels suitable for being mounted in a horizontal sequence together with identical panels, said ribbon-like corrugated panels being provided in cross-section with a broken line profile formed of multiple ribs (1a, 1b, 1c) that are directed towards the center of the carriageway and alternated with grooves (1d, 1e); wherein said panels are provided at each longitudinal end with upper and lower openings (A1, A2, A3, A4) for the insertion of fixing bolts fixing a said panel to the end of the other identical panel, and with intermediate openings (A5, A6) for the insertion of fixing bolts fixing said two panels in overlapped position in said slots (23a, 23b) provided on the lower portion of said bracket; wherein said intermediate openings (A5, A6) for the insertion of fixing bolts are disposed in said corrugated panels in such a position that the heads of said fixing bolts inserted in said intermediate openings (A5, A6) are not disposed in forward position in the direction of the carriageway with respect to said ribs (1a, 1b, 1c) of the corrugated panels; characterized in that the upper portion of the bracket is disposed in contact and fixed to said vertical post of the road guardrail; said ribs (1a, 1b, 1c) and said grooves (1d, 1e) of the corrugated panels have a profile of an isosceles trapezium with obtuse angles; said upper and lower erreh openings (A1, A2, A3, A4) for the insertion of fixing bolts are disposed in said corrugated panels in such a position that the heads of said fixing bolts inserted in said end openings (A1, A2, A3, A4) are not disposed in forward position in the direction of the carriageway with respect to said ribs (1a, 1b, 1c) of the corrugated panels. - a plurality of vertical posts fixed to the ground on the side of a carriageway, and - multiple consecutive ribbon-like corrugated metal panels supported in horizontal position by said plurality of vertical posts; and said motorcyclist-protection barrier comprises: - a bracket comprising an upper portion, and a lower portion that is inclined by an angle (α1) relative to the perpendicular and acts as a shelf; said lower portion of the bracket being elastically flexible and spaced from said post; said lower portion being provided with one or more slots (23a, 23b); - two ribbon-like corrugated panels suitable for being mounted in a horizontal sequence together with identical panels, said ribbon-like corrugated panels being provided in cross-section with a broken line profile formed of multiple ribs (1a, 1b, 1c) that are directed towards the center of the carriageway and alternated with grooves (1d, 1e); wherein said panels are provided at each longitudinal end with upper and lower openings (A1, A2, A3, A4) for the insertion of fixing bolts fixing a said panel to the end of the other identical panel, and with intermediate openings (A5, A6) for the insertion of fixing bolts fixing said two panels in overlapped position in said slots (23a, 23b) provided on the lower portion of said bracket; wherein said intermediate openings (A5, A6) for the insertion of fixing bolts are disposed in said corrugated panels in such a position that the heads of said fixing bolts inserted in said intermediate openings (A5, A6) are not disposed in forward position in the direction of the carriageway with respect to said ribs (1a, 1b, 1c) of the corrugated panels; the upper portion of the bracket is disposed in contact and fixed to said vertical post of the road guardrail; said ribs (1a, 1b, 1c) and said grooves (1d, 1e) of the corrugated panels have a profile of an isosceles trapezium with obtuse angles; said upper and lower erreh openings (A1, A2, A3, A4) for the insertion of fixing bolts are disposed in said corrugated panels in such a position that the heads of said fixing bolts inserted in said end openings (A1, A2, A3, A4) are not disposed in forward position in the direction of the carriageway with respect to said ribs (1a, 1b, 1c) of the corrugated panels.