4. Influence of road surface on noise reduction

4.1 Overview of low-noise road surfaces

• The first generation of low-noise surfacings dates back to the mid-1980s, with the development of draining asphalt concrete (BBDr), or traditional draining asphalt mix. The primary aim of these products was to reduce water splashing and improve skid resistance, by infiltrating rainwater through the 4 cm thick surfacing. Open porosity (20-30%), allowing water to circulate internally, was achieved by a discontinuous grading curve (no aggregates between 2 and 6 mm or between 2 and 4 mm) and a very low sand content (10%). These porous asphalt mixes also absorbed sound and limited its propagation, but they also absorbed fine particles, resulting in pore clogging, more or less rapid depending on traffic intensity, and a reduction...