The NZ Transport Agency is aware of community concerns about noise from the Mackays to Peka Peka Expressway. In response to feedback from residents we have undertaken a number of actions, including the appointment of an expert review panel to evaluate operational noise from the M2PP Expressway. Read the report from the expert review panel and the terms of reference for this review.

Expert review panel report [PDF, 137 KB]
Terms of reference [PDF, 200 KB]

The following actions have already been completed or are underway:

  • Completion of approximately 5 kilometres of resurfacing of the northern section of the expressway with a low-noise asphalt (OGPA) surface.
  • Removal of the outer rumble strip on the left-hand lane.
  • Installation of special monitors that detect heavy vehicles using unsilenced engine brakes. We are using information from this ongoing monitoring to engage with the trucking industry and individual truck drivers to encourage limited engine braking in built-up areas of the expressway (where drivers’ safety is not affected).
  • Installation of advisory signs, asking heavy vehicle operators to limit the use of engine brakes.
  • Smoothing of the bridge joints to reduce noise (2018/19).
  • Monitoring of noise from the remaining median strips (2018/19).
  • Progressing the assessment and offer of potential building and/or property treatments to those specific properties identified in the expert panel review report (note that we have already contacted the identified property owners) (2018/19).

The Transport Agency has agreed to undertake other recommendations identified in the expert panel review report, including:

  • Completing the additional noise monitoring at the specific locations identified in the expert panel report (2018/19).
  • Reviewing the traffic model volume estimate (2018).
  • Update and completion of the project documentation with respect to noise, including preparation of a post-construction review report (2019/20).

The final determination as to whether the Transport Agency has complied with its resource consent conditions is the responsibility of the Kāpiti Coast District Council as the consenting authority.

Expert panel review of road-traffic noise

An expert panel review of noise from the Mackays to Peka Peka Expressway has been completed.

Review of road traffic noise for the Mackays to Peka Peka Expressway [PDF, 137 KB]

Some information relating to individual addresses has been redacted from the report, in order to protect the private information of property owners. 

Owners of the specified properties have been contacted directly by the NZ Transport Agency.

Review of as-built noise mitigation

A review of as-built noise mitigation for the Mackays to Peka Peka Expressway has been completed by Opus International Consultants Limited.   

Review of as-built noise mitigation for the Mackays to Peka Peka Expressway [PDF, 2.6 MB]

This review will be updated once re-surfacing work has been completed on the Expressway.

Frequently asked questions

Noise management

  •   What are the sources of road-traffic noise?

    Many people notice road-traffic noise after a new road is constructed or after an existing road is modified. Because the noise is new and different, it is potentially more annoying. Sounds you may hear include:

    • tyre noise (or road-surface noise) – noise created when the tyre meets the road surface – over the course of a day this will be the dominant source of noise from the Expressway
    • vehicle noise – engine/exhaust noise, rattling of vehicle bodies, noise of engine braking
    • bridge joints – can make a distinctive sound as vehicles pass over them.

    Traffic noise factsheet [PDF, 1.5 MB]

  •   How is noise measured?

    Noise levels are expressed in units of decibels (dB), which are a measure of the air pressure change caused by sound. Measured noise levels include all frequencies, but as our hearing is less sensitive to lower frequencies, the measured levels are adjusted to correspond to human hearing. This adjustment is called “A weighting” and is identified by the letter “A”. Noise level measurements for the Expressway project are ‘A-weighted.’

    Traffic noise levels fluctuate so they are reported as an average value over a period of time. In New Zealand the period of time for which the average is calculated is 24 hours.

    Because decibels are a logarithmic unit, they cannot be averaged like normal numbers, instead the average is determined from the ‘energy levels’ and reported as an ‘equivalent’ noise level on an energy basis. You can think of this averaging as one where louder noises have a disproportionate effect on the average. For example, the average of 40 dB and 60 dB both measured over the same time period is approximately 57 dB (not 50 dB, as with simple averaging).

    In Expressway project information you may see sound levels reported in units of “dBLAeq (24h) “ – this is an abbreviation of the 24-hour continuous sound level equivalent in “A-weighted” decibels (colloquially referred to as the 24-hour average).

  •   What is the Transport Agency doing about engine braking noise from the Expressway?

    Disturbance caused by engine braking is often caused by a small number of vehicle operators. The Transport Agency has found liaising with individual operators is the most effective way to manage engine braking noise disturbance.

    The Transport Agency has installed five monitors to detect engine braking noise and identify individual vehicles.

    The information gathered from these detectors will help us as we work with the trucking industry and individual drivers to limit engine braking in built-up areas along the Expressway.

    The use of the engine braking detectors elsewhere in New Zealand has shown that loud noise from engine braking is not as frequent as objectionable noise from other vehicles (such as motorcycles, modified cars and sirens), or other heavy vehicle noise.

  •   Why hasn’t the Transport Agency installed signs restricting or prohibiting engine braking along the Expressway?

    The Land Transport Management Act limits the Transport Agency’s authority to enact a bylaw prohibiting or restricting engine-braking to roads where the speed limit is 70 km/h or greater. This is because engine brakes are important supplementary safety device for slowing vehicles down in some situations, for example on higher speed roads, such as the Expressway.

    The Transport Agency has installed permanent advisory engine braking signs along the Expressway to ask heavy vehicle operators to limit their use of engine brakes.

  •   How did you decide what noise mitigation to build on the expressway?

    During the consenting phase of the project an assessment of road-traffic noise effects was prepared. This assessment considered the effect of estimated noise levels at existing houses located within approximately 100m of the Expressway.

    The predicted noise levels were estimated utilising a computer model based on future traffic conditions (for the year 2026). The predicted noise levels were compared against the criteria in the New Zealand Standard (NZS 6806).

    In areas where road-traffic noise levels at houses were predicted to exceed the criteria in the New Zealand Standard, a series of options were developed for noise mitigation. These options typically included low-noise surfacing and/or noise barriers or bunds of varying heights and locations.

    A group of subject matter experts then completed a Multi-Criteria Assessment (MCA) of the mitigation options, and selected the ‘best practicable option’ for noise mitigation. These experts considered the acoustic benefit of the options and weighed those up against other factors, such as feasibility, urban design, landscape/visual, safety, storm water, environmental and cost.

    The selected mitigation options and decision-making process is documented in the noise assessment report. Together, these were included as part of the supporting information for the Board of Inquiry, and implementation of the selected mitigation is specifically required as part of the project statutory approvals.

    In summary, the decision-making process around noise mitigation considered the future road-traffic noise levels at individual houses located adjacent to the Expressway and the benefit that the noise mitigation would provide, weighed up against the other factors described above to select the ‘best practicable option.’

  •   Who determines whether the Transport Agency is complying with the noise requirements for the Expressway?

    The final determination as to whether the Transport Agency has complied with its resource consent conditions is the responsibility of the Kāpiti Coast District Council as the consenting authority.

    There are two main steps to confirm that the Transport Agency is complying with the noise requirements for the Expressway:

    1. Confirmation that noise mitigation was implemented in accordance with the project noise mitigation plan.
      • This step is complete; an independent report prepared by Opus Consultants indicates compliance with the noise mitigation plan.
    2. Verification that the computer model used to assess noise exposure and select the appropriate mitigation were sufficiently accurate to meet the requirements of the project’s statutory approvals. The conditions require that the noise monitoring to verify the model predictions takes place in approximately two years after opening of the expressway.
  •   Will the Transport Agency compensate me for the perceived loss of value of my house due to its closeness to the Expressway?

    Where the Transport Agency acquired property, including parts of property, under the Public Works Act (the Act), compensation was provided in accordance with the Act, through the process administered by Land Information New Zealand (LINZ).

    Where properties are adjacent to the expressway but no portion of the property was acquired by the Transport Agency, there is no entitlement to compensation for perceived or actual loss in property value under the Act. Therefore, the Transport Agency does not provide compensation in such situations.

  •   Why aren’t the noise level criteria lower at night when most people are sleeping?

    The level of noise from a road varies over a day depending on things like traffic volume and speed, the mix of individual vehicles on the road (eg, passenger cars and heavy vehicles), as well as the weather conditions and temperature.

    Average noise levels will most likely be highest during commute hours and during the day, when traffic volumes are also highest. Average noise levels from the expressway will reduce over the night and gradually increase again from early morning to the peak morning commute period.

    Noise from individual vehicles does not change throughout the day so everything else being equal, the noise from an individual heavy vehicle or car passing at night or in the day remains the same.

    Outside noise is typically lower at night and as most people also sleep this is when noise is often most disturbing. Some countries have separate criteria for road-traffic noise to address increased sensitivity to noise at night. In New Zealand, the previous “Transit Guidelines” and the current New Zealand Standard use a noise level averaged over a 24-hour period.

    The criteria is based on people’s response to ‘real life’ traffic noise over a 24-hour period, including exposure to noise at night and exposure to individually noisy vehicles. The studies supporting the response to noise are population-based rather than individually-based, and consider annoyance, disturbance and health impacts associated with exposure to road-traffic noise over years.

    So while the New Zealand Standard only provides criteria for noise averaged over 24 hours, those criteria were developed based on people’s response to real-life traffic, including noise at night. The noise metrics tool demonstrates how various noise metrics are incorporated in to the 24-hour average.

    During development of the New Zealand Standard, separate day-night criteria were considered. The committee that developed the standard undertook a review of a number of existing roads in New Zealand, and looked at scenarios where 24-hour criteria were applied versus separate day/night criteria. This review concluded that similar noise mitigation requirements were likely regardless of the choice of whether day/night or a 24-hour average criteria were applied.

    On the basis of this assessment, and the understanding that the 24-hour criteria included people’s response to noise during the night, the committee adopted a 24-hour averaging period for the noise criteria in order to simplify application of the criteria.

    Noise metrics tool
    Fundamentals of sound

  •   What is the New Zealand Standard 6808:2010 and how was it developed?

    NZS 68062010 Acoustics – Road traffic noise – New and altered roads sets out procedures and requirements for the prediction, measurement, and assessment of road traffic noise for new and substantially altered state highways and local roads. It also provides best practice guidance and advice on methods for mitigating reverse sensitivity situations and the environmental effects of noise exposure on nearby noise-sensitive activities.

    The Standard was developed taking into account health issues associated with noise; the effects of noise levels on people and communities; affordability considerations and the potential benefits of roads to people and communities. The Standard recognises, as does the World Health Organisation, “that the evaluation of control options must take account of technical, financial, social, health and environmental factors."

    The committee that developed the Standard, was made up of representatives from a wide range of organisations that include Local Government New Zealand, Ministry of Health, Ministry of Transport, New Zealand Transport Agency, Road Controlling Authorities NZ, Department of Building and Housing, NZ Acoustical Society, NZ Institute of Environmental Health, Roading NZ, and Ingenium.

    NZS 6808:2010 Acoustics – Road traffic noise


Review of Road-traffic noise

  •   Are the noise mitigation features of the expressway performing as expected?

    The project was required to provide the noise mitigation measures (noise walls, noise bunds and low-noise road surface or OGPA) identified in the statutory approvals. Prior to the expressway’s opening an independent consultant determined that the mitigation measures were provided as required. This was also confirmed by the expert review panel.

  •   What is the purpose of noise monitoring?

    The purpose of noise monitoring is to confirm that the model used to predict noise is accurate. The noise monitoring carried out to date suggests that the road noise is consistent with what is predicted in the noise model. The model was used to assess noise exposure and was presented to, and accepted by the 2012 Board of Inquiry.

    While this process is taking place, we’ll continue to:

  •   Will you be doing more noise monitoring?

    The Transport Agency has no plans to undertake additional noise monitoring in response to individual requests or concerns.

    Noise monitoring has been undertaken at a number of representative locations along the expressway since opening. These noise monitoring results were compared to the predicted noise levels from the updated noise model to determine whether the model predictions are sufficiently accurate to meet the project's statutory requirements (a process called model verification or validation).

    The expert review panel reviewed the verification process, and was comfortable that it has validated the noise levels predicted by the model. However, for completeness, the panel recommended some additional monitoring at specifically identified locations.

    The project approvals require additional noise monitoring 2 to 3 years after opening of the Expressway. Once this monitoring is complete the model verification process described above will be repeated, and a summary report provided to the Kāpiti Coast District Council.

  •   Will the Transport Agency be constructing more noise mitigation measures anywhere along the Expressway alignment, i.e. walls, bunds?

    The M2PP Alliance was required to provide the noise mitigation measures (noise walls, noise bunds and low-noise road surface or OGPA) identified in the statutory approvals. Prior to opening of the expressway an independent consultant determined that the mitigation measures were provided as required. This was also confirmed by the expert review panel.

    The panel also reviewed the noise model verification and the as-built noise model results and confirmed that noise exposure levels comply with the statutory approvals.

    We are not considering additional noise mitigation measures i.e. walls, bunds on the expressway.

  •   What were the panel's comments on noise standards?

    NZS 6806 is a New Zealand Standard and applies nationwide. NZS 6806 was prepared under the supervision of a committee which included a number of Governmental bodies, the Acoustical Society of New Zealand and the New Zealand Institute of Environmental Health.

    The panel acknowledged that the Transport Agency is not the author or owner of the Standard.

    The panel did suggest that for future revision of the Standard, the following could be considered:

    • For semi-rural environments, noise effects beyond 100m should be considered.
    • For Category B (<64 dB LAeq (24)) dwellings, whether building modifications should be offered.
    • The use of daytime and night-time criteria.
    • Consideration of discrete noise sources such as bridge joints and rumble strips that are not currently identified in NZS 6806.
    • Considering opportunities for going over and above the minimum requirement in terms of noise mitigation measures.
  •   What are you doing to limit the noise from vehicles driving over the bridge joints?

    The expert review panel recommended improvements to the bridge joints to limit the noise generated when vehicles travel over them.

    Remedial work on the northbound Waikanae Bridge to smooth the ride over the bridge joints has been completed. Remedial work on the southbound bridge joints is scheduled to be completed this year.

    The remainder of the bridge joint remedial work will be programmed alongside resurfacing work, scheduled to begin in the 2018/2019 construction season.

    Once the bridge joint smoothing work has been completed an assessment will be undertaken of noise to determine if additional remedial work is required.

  •   How will you address noise from the 110km/h speed limit increase?

    The expressway been identified as a future length of state highway to be considered for the 110 km/h speed limit, subject to improved safety protection and meeting consent conditions, particularly around noise. Currently there is no timeframe for further investigation of a speed limit increase on the Expressway.

    Any state highways under consideration for the 110km/h speed limit will require technical safety reviews and public consultation. This enables communities and stakeholders to contribute to decisions that will help make travelling by road safer, more predictable and therefore more efficient.

  •   What are the lessons learned?

    The Transport Agency strives to be open and transparent, and we take our social and environmental responsibilities seriously. The expert review panel has identified several aspects that the Transport Agency will take forward to consider on future projects.

    Aside from road traffic, noise is generated from additional sources such as rumble strips and bridge joints, which were not adequately assessed in the Assessment of Environmental Effects (AEE) presented to the Board of Inquiry. These sources of noise are a nuisance for the community.

    Many noise complaints received from the community focus on the noise being greater than anticipated. The expert review panel noted that the community expectations were different to the noise outcome known to the Transport Agency, and suggested the message to the community regarding operational noise was not adequate.

    The Transport Agency will factor the above comments and the expert review panels’ other recommendations, into future roading projects of this kind.


Further information

  • If you wish to voice concerns about a New Zealand Standard, please send them in writing to Standards New Zealand email (Note that the Transport Agency does not own any Standards and cannot change them.)
  • If you have any further enquiries, please contact us by email: