In the past, environmental benefits were not generally viewed as principal objectives in the design and development of new surfacing products. Better mechanical performance and lower cost were the usual design objectives. However, today, environmental impact is a high priority. With respect to road surfacing, the environmental aspects that may be considered range from less traffic congestion and reduction of air pollution to uptake of waste and industrial by-products and energy conservation. However, of all of these, reduction of noise pollution has possibly become the most important as a design objective at the present time. This paper will review the current state of the art in design of road surfaces for reduced noise and illustrate how certain waste products can be used to advantage in achieving the design objective to produce friendlier road surfaces. The paper will cover the developments of porous asphalt and thin surfacings and explain why road surface irregularities are important for noise reduction. Recent guidelines for the design of low-noise pavements will be reviewed and consideration given to design enhancement by incorporation of waste products.
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