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Guide to the management of reverse sensitivity effects on the state highway network

Submissions for this consultation is now closed. Please refer to these published resources:

The Transport Agency released a draft Guide to the management of reverse sensitivity effects on the state highway network for public consultation. This guide describes how the we manage reverse sensitivity effects, working together with territorial authorities and landowners/developers.

The feedback period for this guide closed on 1 May 2015, however, questions can be submitted to environment@nzta.govt.nz.

About the Guide to the management of reverse sensitivity effects on the state highway network

Sensitive activities establishing near existing state highways can be affected by issues such as road-traffic noise, causing health effects such as sleep disturbance. In turn, this can cause reverse sensitivity effects on the state highway network. Appropriate setback distances and criteria for acoustically treating new buildings are provided, together with model district plan rules and resource consent conditions.

The key users of this guide are likely to be:

  • Transport Agency planner
  • council planners
  • developers and landowners
  • acoustics specialists

Useful link: https://acoustics.nzta.govt.nz/ (external link)

Questions and answers

Why is the transport agency updating its reverse sensitivity guidance?

The Transport Agency’s existing reverse sensitivity policy was introduced in 2007. The proposed new Guide to the management of reverse sensitivity effects on the state highway network updates and builds on the approach adopted within this existing guidance. The overall approach with a ‘buffer area’ and ‘effects area’ is retained, but is refined to recognise issues identified with the implementation of the existing guidance over the last eight years. The objective of the new guide is to provide greater clarity on the need to manage reverse sensitivity effects on the state highway network and the likely costs to achieve this. The Transport Agency also seeks to improve the national consistency for managing reverse sensitivity.

Why has this draft guide been released for public comment?

The NZ Transport Agency has reviewed its policy on reverse sensitivity and refined the approach as set out in this new draft guide. Following extensive internal consultation, we are now seeking feedback to ensure the refined guidance in the draft is practical, efficient and effective. In particular, comment is sought from developers, local government, planning, legal and acoustics professionals working in this area.

What is reverse sensitivity?

Reverse sensitivity is the vulnerability of an established land use (such as state highways) to complaint from a newly establishing, more sensitive land use (for example, new houses and other noise-sensitive activities). In practice such complaints can compromise the established land use by restricting when or how it can operate.

Why manage reverse sensitivity?

Unfortunately there is unavoidable noise and other effects associated with highway operation, maintenance and construction. Tension can therefore arise between the Transport Agency’s need to operate and maintain a safe and efficient highway network and the desires of neighbouring land owners to enjoy their property free from interference or nuisance.

While the Transport Agency takes care to minimise unreasonable nuisance or interference, complaints from sensitive receivers still arise. Minimising conflicts through careful planning creates social benefits in that it provides sensitive receivers with greater health and wellbeing while allowing for more efficient movement of people and goods between communities.

Who is this guide for?

Transport Agency and council planners are the primary audience for this guide, but the information is also useful for developers, acoustics specialists and the general public.

This guide provides useful information for people wanting to construct or alter dwellings, accommodation, places of worship, education activities and healthcare activities near to a state highway.

What is the difference between the old guidance and the new guide?

The new guide now includes case studies on the costs of acoustically treating new houses next to state highways; refines the method for calculating the buffer and effects areas by recognising that the percentage of heavy vehicles and the type of road surface influences noise levels (but does not increase the maximum distances from the road within which controls apply); provides guidance on ventilation requirements where windows need to be closed for sound insulation purposes; and provides model district plan objectives, policies and rules.

The new guide is consistent with the 2010 New Zealand Standard NZS 6806:2010 Acoustics – road-traffic noise – new and altered roads.

To support the updated guide the Transport Agency is also developing web based GIS maps to illustrate the recommended buffer and effect areas for the whole state highway network. These maps will be publicly available and will clarify the recommended setback that new noise sensitive activities should be located from the state highway.

The model plan rules in the new guide are slightly less restrictive for developments near state highways compared to the old guidance.

Who is responsible for managing reverse sensitivity effects?

Managing reverse sensitivity effects requires a shared approach. This is because it is neither practical nor reasonable for landowners, councils or the Transport Agency to assume sole responsibility. Careful and considered planning is pivotal to both protecting the environment and enhancing the quality of life for New Zealanders. More information about the shared roles and responsibilities can be found in Section 2 of the draft Guide.

Why shouldn’t I build my house next to a state highway?

Separation is often the most effective method of mitigating effects such as noise, vibration, vehicle emissions, lighting/glare and dust on people in houses. To achieve a reasonable level of internal amenity, the Transport Agency seeks for houses to be located outside of a state highway buffer area, which extends up to 40 metres from the traffic lanes. However, in urban areas and on occasions in other situations it can be impractical to restrict residential development to outside the desired buffer area. Where dwellings (and other noise sensitive activities) need to be located within the state highway buffer area, additional assessment/treatment is required to allow residents to enjoy a reasonable internal amenity free from excess vibration.

Houses can be built in the wider effects area, extending up to 100 metres from the traffic lanes, outside the buffer area, but they need to be designed/treated to ensure internal noise levels are reasonable.

How much does it cost to acoustically treat my house?

Each house (or other noise sensitive activity) in the effects area will require an assessment to confirm the acoustic treatment required to meet the recommended internal noise levels (see Table 1 in the draft guide). This is because site specific characteristics such as the terrain, number of vehicles, type of road surfacing, vehicle speed and the percentage of heavy vehicles all influence the noise exposure, and the resulting internal levels depend on the layout and construction of the house. The cost to acoustically treat a house will therefore vary.

As a guide, professional fees for an acoustic assessment of the design of a house to demonstrate compliance with the specified internal levels may cost $500 to $1000.

The NZ Transport Agency has published a case study of likely costs of the treatment itself. For a typical three bedroom, single storey, 175m2 dwelling located 20 metres from the edge of a highway with a chip seal surface and 9,000 vehicles per day, or next to a road with a porous asphalt surface and 30,000 vehicles per day, the estimated cost for acoustic treatment is $21,900. This cost reduces to $11,900 or $7,900 where the same dwelling is located respectively 60 metres or 90 metres from the edge of the highway. Comparably the cost to acoustically insulate a typical four bedroom, double storey, 225 m2 dwelling ranges from $27,250 to $12,250 to $7,250 where the dwelling is located 20 metres, 60 metres or 90 metres from the highway.

Note that these costs are based on 2013 values.

If I live next to a state highway can close my windows to minimise noise?

Yes, closing windows can significantly reduce the road-traffic noise heard inside a building. In the majority of cases, this is the only measure required to achieve the required internal noise levels. However, closing windows compromises the natural ventilation of a building. Where windows need to be closed to achieve reasonable internal sound levels, mechanical ventilation and cooling will be required. Care should be taken when choosing mechanical ventilation to avoid systems that are excessively noisy or do not avoid environments that are hot or stuffy in summer months. Section 3 of the draft guide provides an appropriate specification for ventilation/cooling systems to achieve reasonable internal amenity.

If I build a solid fence or wall will that block out the noise?

In some instances, barriers such as walls or bunds can result in compliance with the internal noise levels specified. The effectiveness of a noise barrier will be site specific.

Care needs to be taken during the design and location of noise barriers to give consideration to urban design effects and maintenance requirements. To be effective, noise barriers for individual developments need to join up with other noise barriers or extend wider than the area to be protected. Otherwise it may be necessary for the barrier to include return sections at each end of the barrier perpendicular to the highway.

If I plant trees will that block out the noise?

No, trees or shrubs generally provide minimal benefit in terms of reducing noise levels.

Trees and shrubs are a practical method for visually screening noise walls or bunds and reducing graffiti.

What is a noise-sensitive activity?

A noise sensitive activity is defined as follows:

  • any residential activity (including visitor accommodation and retirement accommodation)
  • any educational activity
  • any healthcare activity
  • any congregations within places of worship or marae.

 

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