A module (10, 20, 40, 50) of a road safety barrier for contacting and redirecting an errant vehicle, comprising: - a first beam; - a second beam; - uprights that support the first beam and the second beam, each upright comprising a lower end which is configured to be fixed to the ground and an upper end, opposite the lower end; wherein: - the first beam extends longitudinally from a first upright to a second upright in order to contact and redirect an errant vehicle and is joined between the lower ends and the upper ends, detached therefrom; - wherein the second beam is joined to the upper ends; wherein the first beam comprises a first longitudinal part which projects laterally with respect to the uprights; - the first beam comprises a second longitudinal part which projects laterally with respect to the uprights, on the opposite side of the uprights with respect to the first longitudinal part; - the first longitudinal part and the second longitudinal part are both joined to the first upright and to the second upright by means of joints of a permanent type; the module (10, 20, 40, 50) being characterised in that the first longitudinal part and the second longitudinal part are joined to one another so as to form an internally hollow beam with welds or brazing, longitudinally spaced so as to form longitudinal slots between the first longitudinal part and the second longitudinal part, each longitudinal slot extending between two welds or brazing longitudinally spaced. - a first beam; - a second beam; - uprights that support the first beam and the second beam, each upright comprising a lower end which is configured to be fixed to the ground and an upper end, opposite the lower end; - the first beam extends longitudinally from a first upright to a second upright in order to contact and redirect an errant vehicle and is joined between the lower ends and the upper ends, detached therefrom; - wherein the second beam is joined to the upper ends; wherein the first beam comprises a first longitudinal part which projects laterally with respect to the uprights; - the first beam comprises a second longitudinal part which projects laterally with respect to the uprights, on the opposite side of the uprights with respect to the first longitudinal part; - the first longitudinal part and the second longitudinal part are both joined to the first upright and to the second upright by means of joints of a permanent type; - the first beam comprises a second longitudinal part which projects laterally with respect to the uprights, on the opposite side of the uprights with respect to the first longitudinal part; - the first longitudinal part and the second longitudinal part are both joined to the first upright and to the second upright by means of joints of a permanent type; the module (10, 20, 40, 50) being characterised in that the first longitudinal part and the second longitudinal part are joined to one another so as to form an internally hollow beam with welds or brazing, longitudinally spaced so as to form longitudinal slots between the first longitudinal part and the second longitudinal part, each longitudinal slot extending between two welds or brazing longitudinally spaced.