Abstract: A longitudinal beam barrier system comprises a longitudinal beam and a post linked together via a fastener incorporating at least one deformable washer. The link is made in a releasable and tunable manner dependent on an applied force via the at least one deformable washer. Release may be made dependent on both the magnitude and direction of the force so that release may be a result of different release forces in different force angles. The deformable washer may be designed to transfer a longitudinal beam load force from a fastener to a post wall, the washer extending around the fastener and having a first face that bears on the fastener or a part thereof (or forms part of the fastener) and an opposing face that at least partly bears on a part of the post wall or walls. The washer is designed so that, in the event of an impact of sufficient force on the longitudinal beam, post, or fastener, the washer at least partly deforms allowing separation to occur between the post or posts and the longitudinal beam.