The present invention provides a spacer for a road safety barrier. The spacer includes a post and a rail connected to the post via an intermediary of the spacer and a connector. The spacer includes a rail support having a front face intended to be fastened to a rail, a rear face intended to be fastened to a post and a flange that connects the front face to the rear face. The front face includes a notch emerging on the upper edge of the front face, the notch includes a connector housing, located in the lower portion of the notch and two convergent lateral edges connecting the connector housing to the upper edge of the front face. The present invention also provides a safety barrier including a spacer and a fabrication kit for a safety barrier.