This final report demonstrates the feasibility of employing high molecular weight/high density polyethylene cylinders as the energy dissipating medium in highway safety appurtenances. It is shown that this polymer can dissipate large amounts of kinetic energy, undergo large deformations and strains without fracturing, and essentially restore itself to its original size, shape, and energy dissipation potential when the forcing function is removed. This research involves a quasi-static and impact loading experimental investigation to determine the energy dissipation characteristics of HMW HDPE tubes as functions of temperature, radius to wall thickness ratio, strain, strain-rate, deformation, and repeated and cyclic loading. The results of this experimental program are analyzed to develop analytic energy dissipation expressions which are then employed in the design of truck mounted attenuators (TMA). Finally, an expert system computer program, CADS, is modified to use HMW HDPE tubes in the generalized design of crash cushions. The potential financial, legal, and safety payoffs for highway operations associated with developing highway safety devices which are essentially maintenance free are significant. Maintenance costs associated with the repair of impacted safety devices would be greatly reduced or eliminated. Tort liability exposure related to damaged or collapsed hardware would be significantly decreased. Finally, the safety of the motoring public and the maintenance personnel involved in maintaining and repairing damaged hardware would be enhanced.