The invention relates to an elongate mechanical device for vehicles, for absorbing impacts, which comprises a profiled or tubular elongate part (1) of polygonal cross section, and an end part (2) mounted at one end of the elongate part, at an angle perpendicular to the axis of the elongate part, and intended for fastening to other elements. In the vicinity of its end, the elongate part (1) comprises cutouts, which create adjusted regions or faces (172-173), in the vicinity of edges of its cross section, and there is provided a rigid fastening between the elongate part (1) and the end part (2)that maintains the adjusted regions in direct contact with the end part, the adjusted regions (172-173) being dimensioned to withstand compressive loads and a tilting torque during impacts.