Porous pavement for reduced tyre/road noise and improved air quality - Initial results from a case study

One possible solution to reduce noise resulting from tyre-pavement interaction is to use a porous pavement surface. A porous surface will reduce noise by decreasing air pressure gradients in the tyre-pavement contact as well as by decreasing the acoustical impedance of the road surface and reducing the horn effect. While reducing noise, other functional aspects of a pavement such as abrasion wear which impacts on air pollution through generation and suspension of particles, friction and rolling resistance need to be addressed. This paper analyses the acoustical behaviour of a Double Layered Porous Asphalt (DLPA), applied in the city of Linköping, Sweden, as a solution to mitigate noise, compared to a non-porous Stone Mastic Asphalt (SMA) pavement used as reference. The analysis is based on Close Proximity noise measurements, both in absolute value and as frequency spectra, acoustical homogeneity over the surface length and sound absorption measurements. The acoustic analysis is combined with analyses of air quality measurements of PM10 (Particulate Matter with aerodynamic diameter < 10 µm) from two Tapered Element Oscillating Microbalance (TEOM) measurement stations placed near each different pavement section. The initial results indicate that the porous pavement results in a noise reduction of up to 5 dB for light vehicles, and up to 4 dB for heavy vehicles. So far, the DPLA shows approximately 52 % lower PM10 concentrations than the SMA. It should be noted that PM10 is influenced also by meteorological conditions, like humidity, background sources as well as vehicle properties, e.g. use of studded tyres, and that some of the observed decrease can be due to other aspects than porosity e.g. road surface moisture and wind direction. In conclusion, the use of a porous pavement shows promising results from both acoustical and air quality aspects, given the initial, short term results