Motor Vehicles: Testing

Excessive exhaust noise is currently tested with a subjective assessment at the MOT in which the tester can fail the vehicle if they believe it is producing excessive noise for the vehicle model. The MOT standard for exhaust noise requires that the noise from the vehicle must not be unreasonably above the noise level a tester would expect from a similar vehicle with a standard silencer in average condition.

This standard is derived from the Road Vehicles (Construction and Use) Regulations 1986 (C&U) where regulation 54 states:

“Every exhaust system and silencer shall be maintained in good and efficient working order and shall not after the date of manufacture be altered so as to increase the noise made by the escape of exhaust gases.”

The MOT noise test also meets the requirements of the European Roadworthiness Directive, which all EU Member States are required to comply with.

For most vehicles, the MOT tester will be familiar with the level of exhaust noise to be expected and should have no difficulty in determining whether the noise complies with the standard or not.

Introducing a metered noise test with the use of a calibrated decibel meter to record noise levels more accurately would require approximately 23, 400 garages to purchase and maintain this equipment. In addition, the accuracy of such a test will be difficult to achieve due to localised noise pollution around testing centres, and within a noisy garage environment.