Acoustic Lifecycle Study of the Double-Layer Porous Asphalt on E4 in Huskvarna, Sweden

In 2010 a double-layer porous asphalt concrete (DPAC) pavement was constructed on the E4 motorway through the Swedish city Huskvarna. Earlier experience in Sweden indicated that it was feasible to obtain a high initial noise reduction but due to the widespread use of studded tires in winter, clogging and ravelling created losses of around 2 dB per year, with an expected acoustical lifetime of only 3 years. However, the improved pavement in Huskvarna finally exceeded lifetime and durability expectations by at least 100 %. The first two years, noise reduction fell from the initial 7-8 dB just marginally, compared to an average-age SMA 16 pavement. Now after its 7th year, the pavement had reached its acoustical end of life, with an average noise reduction loss of 0.5 dB per year. This is considered as a break-through for low noise pavements exposed to the winter climate in Sweden and road traffic with most light vehicles equipped with studded tires. This paper presents results of annual noise measurements using the CPX method over the entire lifetime on the DPAC compared to the reference set of SMA 16 pavements. This includes the effects of grinding, cleaning and rejuvenation trials on certain test sections.