Noise Barriers Using Recycled-Plastic Lumber

Increasing public demand for reduced traffic noise levels is generating a growing need for more and better highway noise barriers. Those using conventional materials such as wood, steel, or concrete deplete natural resources and occasionally meet public criticism with respect to aesthetics. Disposal of accumulating plastic waste is another environmental challenge. Barriers that use recycled plastic thus are not only functional but also environmentally beneficial. Such barriers are proposed in this paper. The proposed material is recycled-plastic lumber, a material extruded into standard lumber sizes used by the timber industry. This material has many advantages. It is durable and requires little maintenance, can be cut and fastened like wood, provides several aesthetic alternatives in both color and texture, is highly resistant to insects and graffiti, is readily available, and is thus inexpensive compared to custom-made plastic shapes. Being denser, it should block noise more effectively than wood sheathing of similar thickness. Wood or steel frames are proposed for structural support, with maximum span of the plastic-lumber sheathing limited to 1.22 m (4 ft). The wood or steel frames can be arranged in many configurations for aesthetic purposes and designed to satisfy optimal cost requirements. The proposed systems are competitive with current barriers with respect to initial cost and may have long-term economic benefits because of greater durability, minimal maintenance, and low life-cycle cost.