You are in: Home > Press office > Press Releases Archive > Press Releases 2005 > 007/2005

Press Release 007/2005

Motor vehicles on roads sometimes louder than permissible

Research project indicates noise regulations for motor vehicles require better monitoring

A majority of the population feels very disturbed by road traffic noise. Lower noise levels are possible if cars and trucks were to comply with noise regulations throughout their life cycles. However, this is not the case, as the TÜV Rheinland Group discovered in a project commissioned by the Federal Environment Agency (UBA). There is a whole range of vehicles which no longer comply with so-called noise type test values. Another outcome of the study: the regular biennial motor vehicle check carried out in accordance with the Road Traffic Licensing Regulations is an insufficient check of compliance with noise regulations. The UBA therefore recommends that additional spot checks be carried out during regular inspections at garages in order to detect and correct any deficiencies.

The TÜV researchers carried out so-called field surveillance on select older motor vehicles. Any deviations from noise type test values in the cars and trucks compared to those in new vehicles were recorded.

Six of the nine automobile types tested essentially complied with the noise limit values of the conformity test (noise limit value for vehicle type plus 1 dB(A)). However, 15 of the 54 vehicles tested exceeded the cap for their respective authorized type test value, with the greatest deviation amounting to roughly 3 dB(A). For the six truck types tested, 12 of the 36 vehicles exceeded the conformity limit value, and 20 exceeded the type test value (by almost 4 dB(A)).

In one vehicle type the reason for the high exceedence was a defective viscose clutch. The vehicle manufacturer reacted by modifying the clutch, thereby reducing its noise level. The clutch was replaced in all vehicles of this type still covered by the guarantee, and all new vehicles were fitted with the new clutch.

The limit value for pneumatic noise in one truck type was clearly too high. This was due to the fact that the manufacturer had changed the compressor unit without testing the impact of this change on noise emissions. As a result, nearly 11,000 vehicles had to be retrofitted in order to reduce the increased noise to a level in compliance with regulations. This is an example of how the practice of conformity testing, especially on trucks, is obviously insufficient when such changes in engineering take place. Since manufacturers conduct their own testing, TÜV Rheinland recommends more checks by outside testers as well as a simple testing procedure to assess noise during the regular motor vehicle checks. However, automobile manufacturers have raised objections to these methods and consider such surveillance excessive in terms of costs and benefits. On the other hand, the UBA recommends that at least spot checks of noise emissions be carried out during motor vehicle inspections, keeping in mind the current revisions of international measuring regulations for noise type tests.

The project demonstrates that field surveillance is a useful instrument for detecting changes in motor vehicle noise behavior, especially as long as conformity testing and regular surveillance of motor vehicles are not improved. The UBA recommends that the implementation of this instrument be continued.

The complete research report and detailed information are available from the Federal Environment Agency, Section I 3.3, fax: 030/ 8903 - 2106;
e-mail: michael.jaecker-cueppers@uba.de.

Berlin, 18 February 2005