The Ministry of Transport administers a suite of regulations set out in Land Transport Rules that seek to control sound emitted from an individual vehicle.
If a vehicle fails a subjective exhaust noise test during a warrant or certificate of fitness the owner has the option to repair the exhaust or to pay for a metered objective test. Further information on noise tests for exhausts is available.
Individual driver behaviour is a significant determinant of noise emissions from specific vehicles. Activities such as deliberate modification of vehicle exhaust systems, lack of maintenance and aggressive acceleration and deceleration can lead to loud and distinctive noises of short duration cause annoyance or disturbance.
Driver education can either be general or site specific. General education approaches may involve driver education and training as part of driver licensing and ongoing training. Site specific approaches may involve signage, noisy vehicle enforcement programmes and traffic calming.
Engine braking is a safety and efficiency feature on trucks which enables faster and more controlled slowing of trucks while reducing brake wear.
Whilst beneficial for safety, if used without effective silencers the systems can produce high levels of noise with unpleasant audible characteristics. It is generally an issue for certain types of older trucks, as new trucks are designed to suppress or avoid this noise.
However, some of the current fleet of trucks without modern engine braking systems or effective silencers may be operated for some time into the future.
Further details can be found in this leaflet [PDF, 331 KB].
Information on how the Transport Agency manages noise disturbances from trucks engine braking on state highways can be found in this technical memorandum [PDF, 75 KB].
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