Noise reducing pavements - State of the art in Denmark

Noise is one of the most serious environmental problems caused by road traffic.About 28 % of all Danish homes are exposed to more than 55 dB, which is the official recommended noise limit for road traffic noise.The Danish government has a long-term goal to reduce the noise to a level that is considered satisfactory for the health.Ac-cording to the national road noise strategy, one of the most cost-effective means of noise abatement is the use of noise-reducing pavements.In this report, the on-going Danish research to develop and test different types of noise-reducing pavements is presented and discussed.Single-layer porous pavements with a high built-in air void and a small maximum aggregate size have been tested on a highway with a speed-limit of 80 km/h.Over the structural lifetime, the noise reduction of the porous pavements was 3-4 dB relative to dense asphalt concrete with a maximum aggregate size of 12 mm.In order to achieve the same noise reduction, the traffic volume should be reduced by more than 50 %.On an urban test road with a speed-limit of 50 km/h, similar single-layer porous pavements have been tested.Here, the observed noise reduction of 3 dB disappeared within 2 years, because the pores of the pavement were clogged.Three new types of two-layer porous asphalt are now being tested on an urban road with a speed limit of 50 km/h.These pavements are designed and constructed to avoid clogging and to improve durability.The pavements are cleaned with special equipment using water under high pressure twice a year.After four years, noise reductions of approximately 3 dB have been measured compared to a dense asphalt concrete with a maximum aggregate size of 8 mm.In order to develop new types of cost-effective noise-reducing pavements for urban application, research and testing of different kinds of thin surface layers have been started in the framework of an EU research project (SILVIA).