An assembly suitable for example for use as a road traffic barrier comprises a rail (1) having one end of a flexible tether (2) secured thereto, and a post (3) provided with an aperture (10, 12, 15) e.g. of the slot or key-hole type, through which the flexible tether can be passed. The other end of the tether is provided with an enlarged head (8) which in at least one orientation with respect to said aperture is incapable of passing therethrough. A locking element (5) is releasably engageable with the post to restrict the aperture and prevent both passage of the enlarged head therethrough and removal of the end of the tether therefrom. Said locking element (5) can form part of a warning lamp unit (6) adapted to be engageable into and releasably lockable in the open end of a tubular post.
