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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.

NZ Transport Agency Waka Kotahi (NZTA) 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, NZTA 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.

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