Road safety barrier comprising: concrete bottom parts (1); concrete top parts (2) coupled on the bottom parts (1), and attaching means (3, 31) of the successive top parts (2) at their opposite ends. The bottom parts (1) have an upper surface provided with a longitudinal channel (11) for coupling in the longitudinal direction and with the possibility of limited vertical displacement of a longitudinal extension (21) protruding from a lower surface of the top parts (2); the channel (11) and the extension (21) have similar cross-sections and dimensions calculated so that the top part performs a lateral rotation of a determined amplitude, in the event of a vehicle impact, and absorbs a significant part of its kinetic energy.