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Vehicle noise emissions regulation

The Ministry of Transport administers a suite of regulations that seek to control sound emitted from an individual vehicle.

Amendments to the Land Transport Rule: Vehicle Equipment 2004 (known as Land Transport Rule: Vehicle Equipment Amendment 2007) came into force on 1 June 2008. The amendments tighten-up the subjective noise test procedure for vehicles with modified exhaust systems at Warrant of Fitness inspections. If the vehicle fails a warrant or certificate of fitness for excessive noise the owner has the option to repair the exhaust or to pay for a metered objective test. The amendments to the rule also reduced the decibel limit for new and used vehicles entering the fleet. Further information on noise tests for exhausts is available.

Sound emitted from an individual vehicle is normally a transient event and can be assessed against LAFmax limits. However, sound levels emitted by the combination of vehicles in traffic flows are assessed using LAeq (LAeq(24h)) as the metric.

Driver behaviour

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 peak noise events that 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. Of these, signage is a useful mechanism to reduce some types of vehicle noise, particularly by encouraging the use of alternative routes.

Overall, driver education complements other solutions, rather than being a stand-alone solution that gives measurable short-term results.

Engine braking noise

Engine braking is a safety and efficiency feature on trucks which enables faster and more controlled slowing of trucks. Whilst beneficial for safety, the systems can produce high levels of noise with unpleasant audible characteristics. It is generally an issue for older trucks, as new trucks are designed to suppress or avoid this noise. However, the current fleet of trucks without these modern engine braking systems will be operated for some time into the future, so dealing with the problem is still needed in the short term. 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].

For further information contact