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The type and condition of a road surface can have a noticeable effect on the noise levels experienced by residents adjacent to state highways.


We have prepared a Guide to state highway road surface noise to aid our staff and contractors with the design, construction and maintenance of road surfaces. This guide has been produced to inform roading practitioners, contractors and the public about how road surfaces affect noise levels and what low-noise road surfaces are available in different situations. Information is also provided on maintenance issues and basic engineering considerations.

Additional information on low-noise road surfaces is available in:

Case studies

Case studies on projects involving road surfaces are available to supplement those discussed in the guide. The case studies report on key lessons learnt from Transport Agency projects for the benefit of future projects.


Our requirements for low-noise road surfaces are included in the P40 specification.

For further information contact

Road surface noise research

Note that the instrumentation and analysis have been refined over the course of this research programme. Some of the absolute levels reported in these reports need to be adjusted before comparing to other ISO standard measurements.




Filename & link

Road surface noise research 2016-2018 (CPX trailer development and initial measurement results)

April 2018


Road surface noise 2016-2018 (Summary Report).pdf [PDF, 4.3 MB]

Road surface noise measurements of porous asphalt on the Waikato Expressway and Tauranga Eastern Link

17 January 2019

Altissimo Consulting Ltd

Road surface noise 2018 (Waikato Expressway and Tauranga Eastern Link).pdf [PDF, 6.5 MB]

NZTA Road Surface Noise Research Programme 2018 – Close Proximity versus Wayside Measurements

30 April 2019


Road Surface Noise 2018 (CPX and SPB Comparison).pdf [PDF, 901 KB]

Road surface noise research Porous asphalt variability study – preliminary results

30 June 2019

Altissimo Consulting Ltd

Road surface noise 2019 (Porous asphalt variability).pdf [PDF, 9.3 MB]

Road surface noise - Measurements of porous asphalt on the Auckland Motorways

11 July 2019

Altissimo Consulting Ltd

Road surface noise 2019 (Auckland Porous Asphalt).pdf [PDF, 12 MB]

NZTA Road Surface Noise Research Programme 2018/2019 – Preliminary Chipseal Study

11 July 2019


Road surface noise 2019 (Preliminary chipseal study).pdf [PDF, 625 KB]

Masterton chipseal trial tyre/road noise measurements

4 September 2019

Altissimo Consulting Ltd

Road surface noise 2019 (Masterton chipseal trial).pdf [PDF, 6.4 MB]

Road surface noise research Porous asphalt variability study – final report

24 January 2020

Altissimo Consulting Ltd

Road surface noise 2019 Porous asphalt variability).pdf [PDF, 11 MB]

Low-Noise Road Surfaces Performance Monitoring


February 2014


Opus-Report-Low-noise-surface-monitoring.pdf [PDF, 1.6 MB]

Research Report 326 Road surface effects on traffic noise – stage 3: selected bituminous mixes




326.pdf [PDF, 309 KB]

Research Report 083 Road noise generated by concrete block pavements




083-Road-noise-generated-by-concrete-block-pavements.pdf [PDF, 1.5 MB]

Research Report 292 Road traffic noise: determining the influence of New Zealand road surfaces on noise levels and community annoyance



292-Road-traffic-noise-determining-the-influence-of-New-Zealand-road-surfaces-on-noise-levels-and-community-annoyance.pdf [PDF, 386 KB]

Drive-by Vehicle Noise

February 2000


Opus-Report-Drive-by-Vehicle-Noise.pdf [PDF, 1 MB]

Initial Review of Aggregates with respect to Road Traffic Noise

15 April 2020


Road surface noise 2020 (Aggregate review).pdf [PDF, 823 KB]

Road surface noise – Influence of axle motion on CPX level


1 May 2020


Road surface noise 2020 (axle motion).pdf [PDF, 5.2 MB]


Close Proximity Monitoring Trailer Guidance/Information




Filename and link

Close proximity (CPX) road surface noise measurement trailer guide

April 2018 


Road surface noise (CPX measurement trailer guide).doc [DOCX, 10 MB]

CPX Trailer Instrumentation Specifications

 13 July 2017 


Road surface noise (CPX Trailer Instrumentation Specification).doc [DOCX, 1 MB]