THIN OPEN LAYERS AS NOISE REDUCING PAVEMENTS

Twin-layer porous pavements can reduce noise on urban roads. They are more expensive than ordinary pavements. Cheaper types of noise reducing pavements are needed; pavements which are cost competitive compared to "ordinary" pavement types, but have a noise reducing capacity. In Denmark, a project was started in 2003. The goal is to develop and test open thin layers as noise reducing pavements under Nordic conditions. This is a part of the European SILVIA project started in September 2002. Thin open pavements are open only at the upper part of the pavement structure having a depth less than the maximum size of the aggregate. The basic concept for noise reduction is to create a pavement structure, with as big cavities at the surface as possible in order to reduce the noise generated from the air pumping effect, and at the same time ensuring a smooth surface to reduce noise generated by the vibrations of the tires. Eleven test sections have been constructed. Different types are included: 1. Open graded asphalt concrete. 2. Stone Mastic Asphalt. 3. A thin layer constructed as a combination pavement. Dense reference pavements with 8 and 11 mm aggregates are included. A comprehensive measurement program will cover noise, structural behaviour, durability, traffic safety and energy consumption. Noise measurements are performed by the Statistical Pass-By Method. The pavements are presented together with the first series of noise measurement results.