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National air quality (NO2) monitoring network

Published: | Category: Nationwide statistics , Statistics & surveys | Audience: Local & regional government

The state highway system accounts for about 12% of New Zealand’s roads and around half of the 40 billion vehicle kilometres New Zealanders travel each year. Motor vehicles travelling on roads emit an array of air pollutants which can contribute to harmful effects on human health and smog formation.

Waka Kotahi NZ Transport Agency is committed to being socially and environmentally responsible and has specific objectives in its state highway environmental plan for improving air quality, including:

  1. Understand the contribution of vehicle traffic to air quality.

  2. Ensure new state highway projects do not directly cause national environmental standards for ambient air quality to be exceeded.

  3. Contribute to reducing emissions where the state highway network is a significant source of exceedances of national ambient air quality standards.

In 2007, Waka Kotahi began a national monitoring programme to determine relative levels of vehicle pollution across the state highway network. Passive samplers are now located at more than 120 sites across New Zealand to measure nitrogen dioxide (NO2) as a proxy for vehicle-related air pollution. The overall aim is to see a decreasing trend in NO2 concentrations measured at these sites. This aligns with the government’s desired long-term impact which seeks a ‘reduction in adverse environmental (air quality) effects from land transport’ as stated in the Government Policy Statement on land transport.(external link)

The annual report summarises the data measured at the national network sites since 2007. It is complemented by a metadata report, which provides details for each site in the network, and an operating manual which outlines how the network is operated.

Related information

Air quality

Publication details

  • Author:
  • Published: October 2016
  • ISBN/ISSN: ISBN 978-0-9941397-7-1
  • Contact:
  • Also known as: NO2 monitoring report

Annual reports

Year Published date
2007–2012 annual report [PDF, 9.1 MB] Oct 2013
2007–2013 annual report [PDF, 7 MB] Mar 2015
2007–2014 annual report*  
2007–2015 annual report* Oct 2016
2007–2016 annual report* Nov 2017
2007–2019 annual report [PDF, 2.1 MB] Aug 2020
2007–2020 annual report [PDF, 1.3 MB] Aug 2021
2007–2021 annual report [PDF, 1.3 MB] Dec 2022
2007–2022 annual report [PDF, 973 KB] June 2023

*These annual reports are available on request from It should be noted that data contained within these reports, for the 2013 year, has been found to include errors (affecting 2013 annual and seasonal averages). 

NO2 monitoring results

Ambient air quality NO2 monitoring data 2007-2022 [XLSX, 1.5 MB]

Site metadata reports

Year Published date

2007–2011 site metadata - Whangārei, Auckland [PDF, 6.9 MB]

2007–2011 site metadata - Hamilton, Wellington [PDF, 6.9 MB]

2007–2011 site metadata - South Island [PDF, 3.4 MB]

Jun 2012
2007–2010 site metadata [PDF, 13 MB] May 2011
2007–2012 site metadata [PDF, 5.4 MB] Apr 2013
2007–2020 site metadata [XLSX, 1.4 MB] Aug 2021
2007–2021 site metadata [XLSX, 1.4 MB] Dec 2022

Operating manuals

Year Effective date
2012–2013 operating manual, first edition [PDF, 1.7 MB] Sep 2012
2013–2014 operating manual, first edition [PDF, 2.9 MB] Sep 2013
2017–2018 operating manual, third edition [PDF, 9 MB] Oct 2017

Supporting documents

Title Published date
Air quality monitoring in The Terrace and Mt Victoria Tunnels, Wellington [PDF, 3.7 MB] Jun 2009
Trends in transport related air pollution in NZ (CASANZ Transport Special Interest Group presentation) [PDF, 1.2 MB] Sep 2013

Trends in air quality impacts from roads in New Zealand 2007–2016 [PDF, 613 KB]

May 2017

Review of the National Air Quality Monitoring Network – NIWA [PDF, 2.8 MB]

Jan 2021