Thin noise-reducing asphalt pavements for urban areas in Germany

The objective of the research was the development, optimisation and evaluation of thin noise-reducing surface layers in Germany intended to be more durable than porous asphalts, thus providing better long-term acoustical properties. The basic approach was to create a smooth, open-textured surface with a stone mastic asphalt-based aggregate skeleton across the whole thickness of the layer. The test pavements in Düsseldorf were subjected to both optical 3D measurements of surface texture parameters and the continuous close-proximity method monitoring of the noise emission. The test pavements had significant noise reduction and very low changes in acoustical properties over time, and when compared to other common types of surface layers they showed the highest noise-reducing capacity. On the basis of the research results and past experience, recommendation on the specification according to the relevant European standards was developed, thus contributing to the adoption of European specifications for noise-reducing asphalt pavements.