Low noise road surfaces

Abstract The results of measurements carried out at 22 main road sites surfaced with pervious bituminous materials have confirmed that the low levels of vehicle noise observed for these surfaces, when constructed under laboratory conditions and tested with single vehicle noise sources, were also achieved under normal road conditions and for random vehicles drawn from the traffic stream. The average reductions in vehicle noise obtained, when compared with conventional surfacings with the same skid resistance index, ΔBFC, were approximately 5 dB(A) for ‘light’ vehicles and 4 dB(A) for ‘heavy’ vehicles. The noise reductions obtained were not found to be dependent on the age and corresponding wear of the surface over the period 3–110 months, or to the skidding resistance of the surface, ΔBFC, over the range −22 to +23%. The results suggest that the low noise characteristics of pervious road surfaces are a result of the high acoustic absorption provided by these surfaces.