NOISE FROM VEHICLES RUNNING ON OPEN TEXTURED ROAD SURFACES

The results of measurements carried out at 16 main road sites surfaced with open-textured bituminous materials have confirmed that the low levels of vehicle noise observed for these surface types 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, deltabfc, were approximately 4 db(a) for "light" vehicles and 3 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 43 to 110 months, or to the skidding resistance of the surface, deltabfc, over the range -33 to +13 per cent. The results suggest that the low noise characteristics of open-textured road surfaces are due to the high acoustic absorption provided by these surfaces. (Author/TRRL)