DRAINOR - ROADSURFACES. A MEASURE TO REDUCE ROAD NOISE

Cavity filled surfaces known as 'drainage asphalts' are available in Germany and Sweden and have the advantages of reduction in traffic noise and drainage of surface water. Although ideal in theory it is suggested that they are not in widespread use because of difficulties in mixing and laying. Measures are described which have attempted to overcome these problems such as the lower temperatures, polymer-modified binders and a harder binding material. The results were unsatisfactory and led to the development by skanska of a new surface, drainor. It was specified that this surface would have to be made from unmodified bitumen at normal temperatures and low cost. It must also be able to be laid by hand, have good damage resistance and handle like a conventional surface in mixing. To produce these properties a fibre additive, inorphil, is added to the bitumen. The origin of road noise is traced and the mechanism of the effectiveness of drainor surfaces in cutting down noise explained. Measurements carried out in goteborg showed reductions in registered noise of up to a half. Reduction in noise was greater at higher speeds. (TRRL)