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The method of measuring the noise of powered vehicles is directed primarily at reducing engine and transmission noises as the most powerful sub-sources. But tyre-road-noise is also an important element of the overall nuisance so that a reduction in the noise limits for the homologation test is no longer necessarily associated with a reduction of noise emissions in traffic. Special test series on random traffic samples covering the entire range of vehicle types were carried out in order to reassess noise emissions in real traffic.

The acceleration process on which the noise measuring method for the homologation test is based yields extremely high acceleration values associated with enhanced tyre-road noise contributions, which are not mirrored under real driving conditions. Measures taken by tyre manufacturers to reduce tyre-road noise in these atypical operating modes do not necessarily lead to a reduction of tyre-road noise in real traffic. The German Federal Environmental Agency (UBA) has commissioned extensive studies of driving behaviour in cars and commercial vehicles under real traffic conditions in order to evolve a concept for an improved noise measuring method, whose guiding principles and structure are presented