Assessment processes
The Transport Agency utilises a stage-wise approach for assessing environmental effects (including air quality) of roading projects.
Background air quality
Background air quality is the level of contaminant across the airshed from all sources. This includes contributions from natural sources (eg volcanoes, forest fires, wind-blown dust, etc) and from human-generated sources (eg industry, domestic heating and ‘remote’ roads).
Meteorological datasets
Air dispersion models are often used to assess potential air quality impacts arising from major roading projects. In order to run a dispersion model, you need input data on the meteorology, emissions, local topography and sometimes ambient or background concentrations of pollutants.
Vehicle emissions prediction model
The Vehicle Emissions Prediction Model (VEPM) has been developed by the Transport Agency and Auckland Council to predict emissions from vehicles in the New Zealand fleet under typical road, traffic and operating conditions. The model provides estimates that are suitable for air quality assessments and regional emissions inventories.
Vehicle emissions mapping tool
The Transport Agency has developed a vehicle emission mapping tool that automates calculation of both harmful air pollutants and greenhouse gas emissions. The tool is housed in a geographical information system (GIS) framework so that data can readily be presented as maps. The tool can be applied to all public roads throughout New Zealand.
