There are a variety of alternatives to address land transport noise including technical and legal options, physical works and land use planning.
Technical options are implemented through vehicle and infrastructure design, where noise is generally considered for reasons of user comfort. Noise also needs to be considered throughout the transport life-cycle. This involves addressing noise from the design stage and during vehicle use and movement. Controls on noise emitted from vehicles reduce the need for control at other stages. Vehicle manufacturers and government groups both play a role in controlling vehicle noise.
Technical options can achieve moderate noise reduction and include:
- Quiet tyre technology - tyre design affects noise levels, noise increases with the size of the rim and tyre width. Noise levels also change over the life of the tyre.
- Low noise road surface - noise emitted from road surfaces varies from 9-15 dBA depending on the type. Road texture also influences noise levels - smoother road surfaces generate less noise.
- Noise barriers - a noise barrier acts as an acoustic shield by interrupting the propagation of sound waves.
- Acoustic insulation on buildings - building can be insulated from noise through double glazing and sound-proofing material in wall cavities.
- Low vehicle speeds - noise increases with vehicle speed and engine size. By decreasing the speed limit, noise is reduced. However, in order to be effective a substantial reduction is necessary.
- Congestion controls - noise increases with vehicle numbers. However, substantial reductions are necessary for any real improvement. A reduction in traffic volume of 50% is necessary to achieve noise reduction of 3dBA.
- Rail track grinding or smoothing - rough railway tracks increase noise levels. By smoothing rail tracks noise from bumps and imperfections are reduced.
- Sound absorptive rail track beds - specifically designed railway beds can help to reduce noise emissions.
Technical options can be expensive, particularly when used for retrofitting along road corridors with noise problems.
Legal options revolve around the various enforcement mechanisms for noise. Section 16 of the RMA provides an overall requirement to adopt the best practicable option to avoid unreasonable noise.
There are a variety of issues with the application of section 16 to land transport noise, including establishing who is the "occupier", what the scope of the best practicable option may be and what constitutes a "reasonable level" of noise.
Local authorities are generally familiar with the RMA provisions controlling excessive noise. While land transport noise may be sufficient in some circumstances to "unreasonably interfere with the peace, comfort, and convenience of any person", noise emissions from vehicles on roads and trains are specifically excluded from this enforcement option.
The vehicle noise enforcement provisions of the Land Transport Act 1998, the Land Transport [Road User] Rule 2004, vehicle testing at Warrant of Fitness and Certificate of Fitness (under Land Transport Rule: Vehicle Equipment 2004) and the possibility of bylaws to control vehicle noise, are intended to control individual vehicle noise, rather than the RMA.
By laws under the Local Government Act 2002 provide many local authorities with a means to control motor vehicle noise emissions, particularly heavy vehicles. This is usually done by controlling heavy vehicle movements along certain routes and restricting the use of "engine brakes".
A combination of technical and land use planning solutions is usually necessary to achieve effective noise management although the emphasis in this note is on the latter.
Land use planning options attempt to address noise in a strategic manner. They provide consistency and certainty when implemented early in the planning process. Land use planning approaches to control the effects of land transport noise can occur at national, regional or local levels and can be complemented by other measures such as bylaws (eg, restrictions on engine braking) and urban design.
- Local approaches: district plan objectives, policies, rules and associated standards, noise barriers, building design, setbacks, site layout and building orientation.
- Regional planning approaches: regional land transport plans, district and regional planning policies such as restrictions on sensitive activities along transport corridors, urban design and mixed use development.
- National approaches: National environmental standards, the Government Policy Statement on Land Transport and New Zealand Land Transport Programme, Transport Strategy, New Zealand standards, building codes, Urban Design Protocol.
This guidance note focuses on local approaches to planning for land transport noise. Further information on other approaches is provided in the Land Transport guidance note.