The aim of this report is to develop and test new types of road surface with better traffic noise characteristics than those used today without compromising other important characteristics such as friction, durability etc. This means that the surfaces must result in lower traffic noise emission than on conventional dense asphalt concrete surfacings. The project has been split into sub-projects conducted in Norway, Denmark and Sweden, consisting of literature studies and experimental investigations. Taking both literature studies and the experimental projects in the Nordic countries into account, it is concluded that the optimum noise reducing road surface for Nordic conditions, from an overall acoustic view but also pertaining to road construction, is a drainage asphalt with a max. chipping size of 10-12 mm and an air voids content of 22-23%. Such a surface normally reduces noise emission from road traffic by 3-5 dB(A), compared with a dense asphalt concrete, both in urban traffic (free flowing at 50-70 km/h) and in highway traffic (70-110 km/h). This is applicable to surfaces in new condition. Finally, the report includes recommendations as to the use of drainage asphalt for achieving lower traffic noise emission in various traffic situations considering the use of studded tyres. (A)
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