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The Transport Agency commissions independent research on a number of transport and air quality related issues.

Research reports


Research report 559 - Identify the uses of emerging sources of digital data to assess the efficiency of the state highway network

Published: November 2014

Digital data from emerging sources such as GPS, Bluetooth and weigh-in-motion is currently captured in New Zealand for a range of traffic monitoring purposes. This research project was undertaken to provide guidance on what capacity exists to assess the performance of the state highway road network using these digital data sources. This report summarises the background research, model development and delivery, and future opportunities to understand the performance of the state highway road network, both spatially and over time, using emerging digital data technologies.


Research report 516 - Detailed observations and validated modelling of the impact of traffic on the air quality of roadside communities

Published: February 2013

Detailed observations of air quality and local meteorology were conducted on either side of a stretch of the Auckland southern motorway, and in the surrounding residential neighbourhood. The data revealed emissions from motorway traffic contributed, on average, to a 10% elevation in concentrations of particulate matter at a roadside site relative to a setback site (150m away or more) and to a doubling in concentrations of nitrogen dioxide. National environmental standards for air quality were not exceeded, but international health research indicates that the spatial variation in traffic-related air pollutants observed in this study represent a risk that is not currently accounted for in risk assessments in this country.


Research report 457 - Determination of personal exposure to traffic pollution while travelling by different modes

Published: November 2001

The purpose of this project is to assess the comparative risk associated with exposure to traffic pollution when travelling via different transport modes in New Zealand cities. Concentrations of the key traffic-related pollutants (particulate matter: (PM): PM10, PM2.5, PM1; ultrafine particles (UFPs) and carbon monoxide (CO)) were simultaneously monitored on pre-defined routes in Auckland and Christchurch during the morning and evening commute on people travelling by car, bus, on-road bike, train (Auckland only) and off-road bike (Christchurch only) from February to May 2009. Major differences were found by mode, by pollutant, v=by time of day and by distance from the roadway.


Research report 451 - Tools for assessing exposure to land transport emissions

Published: August 2011

Existing roadside air assessment tools are either crude and conservative, or are complex and demanding with no guarantee of improved accuracy. Neither approach is well suited to health risk assessment and both present substantial uncertainty for regulatory use. In this project, a roadside corridor model was developed as a parameterised implementation of a more complex emission-dispersion model. It is implemented as a spreadsheet, suitable for integration into a GIS-based tool. Several practical applications of the model are demonstrated, including road project assessment, risk 'corridor' definition, and disaggregation of local and remote sources in roadside air quality monitoring data.


Research report 441 - Are the harmful emissions from New Zealand's light duty vehicle fleet improving?

Published: May 2011

Vehicle emission reduction technologies are continually improving. However, it is unclear how much influence new technology and improved fuel is actually having on the 'real-world' emissions from the light duty vehicle fleet as a whole. This project used remote sensing to measure real-world vehicle emissions in Auckland in 2009 and then compared the results with measurements taken at the same sites in comparable campaigns undertaken in 2003 and 2005. The results confirmed that New Zealand's light fleet emissions are indeed generally improving with current trends. However, three trends of concern were identified and require on-going monitoring.


Research report 368 - Long-term dust suppression using the Otta seal technique

Published: March 2009

Research was undertaken at four trial sites around New Zealand, to compare the performance and life cycle costs of the Otta seal with waste oil and other dust minimisation techniques for unsealed roads. The research concludes that the Otta seal is the most effective dust minimisation technique available, and the most cost-effective treatment based on life cycle costing. The report also concludes that the use of waste oil as a dust minimisation treatment should be banned. A guideline for the construction of these seals was developed as part of the research.

Research papers


Roadside increments in PM10, NOx and NO2 concentrations observed over 2 months at a major highway in New Zealand (Air Quality, Atmosphere & Health) (external link)

Published: November 2014

Air quality management can be better informed by empirical data that quantifies the increase in concentrations at the roadside relative to urban background concentrations. This paper describes results from an observational campaign conducted in Auckland. The analysis focusses on variability in the roadside increment, particularly as a function of wind direction.


The development, use and value of a long-term on-road vehicle emission database in New Zealand (Air Quality and Climate Change) [PDF, 190 KB]

Published: August 2013

Remote sensing campaigns in Auckland, New Zealand, in 2003, 2005, 2009 and 2011, have yielded a database with real-world emissions records for approximately 146, 000 vehicles. In this paper we describe the development of the database, and the important features which make it a valuable research and regulatory tool for managing vehicle emissions in New Zealand. We then provide key examples of how the database has been applied to date, including analyses of fleet and emissions trends from 2003 to 2011; comparisons between emissions measured by remote sensing and those predicted using the Vehicle Emissions Prediction Model; and how emission factors derived from the database compare with those used in the Auckland air emissions inventory. We conclude by discussing other potential applications for the database, and plans for its ongoing development and maintenance.


Trends in air quality impacts from state highways in New Zealand 2007-2012 (Air Quality and Climate Change)

Published: August 2013

The NZ Transport Agency is a Crown entity responsible for managing almost 11,000 kilometres of state highways in New Zealand. Emissions from the state highway network are assessed annually using passive sampling data gathered at selected sites with nitrogen dioxide (NO2) taken as a general proxy for motor vehicle-related air pollution. The overall aim is to see a decreasing trend in NO2 concentrations. This aligns with the NZTA’s desired long term impact which seeks a ‘reduction in adverse environmental (air quality) effects from land transport’. This paper describes the key features of the network, reviews the trends seen in the data since monitoring commenced in 2007, highlights some of the logistics involved and indicates future plans for the programme.

Tunnel reports

Remote sensing reports

Vehicle emissions prediction model reports

Disclaimer: The views expressed in the above research reports and papers are the outcomes of independent research, and should not be regarded as being the opinion or responsibility of the Transport Agency. The material contained in the reports should not be construed in any way as policy adopted by the Transport Agency or indeed any agency of the NZ Government.

For further information contact environment@nzta.govt.nz.

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