Noise-reducing road surfaces in the practice

Owing to the proceeding construction of roads with constantly widening motorways and major roads, higher noise barriers and more extensive passive noise control measures are needed to meet the legal requirements on noise control. The situation in the cities is often marked by a constantly increasing density of residential and office areas, which is accompanied by an increase of traffic. However, in such a situation it is hardly possible to build noise barriers in order to reduce traffic noise.

One of the most efficient noise control measures is noise abatement directly at the source. By noise abatement at the source, only small interventions in the land, the townscape or landscape or even in private or industrial properties are required. One of the most essential noise sources in road traffic is the tyre-road noise, i. e. the noise of the tyre rolling on the road surface. By the design of the road surface, this type of noise can be reduced very effectively, without affecting the other functional properties. Some of the most efficient road surfaces are so-called two-layered porous asphalts (2PA). Due to their additional sound absorbing property — apart from their noise reducing texture — these road surfaces have the ability to distinctly reduce not only the rolling noise of car tyres but also of truck tyres. So far, this is the only construction method, which "works" both for car tyres and for truck tyres, and that in the velocity range starting from 50 km/h, i. e. especially in inner-city situations. With the two-layered construction, the acoustic efficiency of drainage asphalts is further improved and at the same time the operational disadvantages of porous constructions are distinctly reduced.

The 2nd symposium focused on this new generation of highly efficient noise-reducing road surfaces. At the conference, the participants were informed about the latest findings from tests with the road pavement 2PA in inner-city situations, which was used in Germany for the first time. MÜLLER–BBM, the city of Augsburg, the Bavarian Environmental Protection Agency (Bayerisches Landesamt für Umweltschutz), the Institute for Road Traffic Systems (Institut für Straßenwesen) of RWTH Aachen, the project office Hillebrand and the construction companies CTS Bitumen and Lorenz Leitenmaier gave lectures about the basis and all steps of this pilot project, which is supported by the Bavarian Ministry for Environmental Protection, Health and Consumer Protection (Bayerisches Staatsministerium für Umwelt, Gesundheit und Verbraucherschutz) and supervised by the city of Augsburg. Subject of the lectures were the planning, the preparatory and accompanying measures and investigations during the construction phase and the experience with the road operation services in the first winter term. In order to give the approximately 60 participants an impression of the construction and effect of the 2PA road surface, an excursion to the test track on the major road B17 in Augsburg was also included in the conference program.

In their introductory lectures, Christoph Himmighoffen (president of the Bavarian Environmental Protection Agency (Bayerisches Landesamtes für Umweltschutz)), town councillor Schaller (environmental health officer of the city of Augsburg) and Dr. Wende from the Federal Environmental Agency (Umweltbundesamt) impressively described the importance of traffic noise abatement at the source for country, cities and municipalities as well as for the people affected by that noise. In a most interesting off-topic lecture, Dr. Gauterin (Continental AG) informed about the noise reduction potential of tyres and the conditions needed to develop this potential.