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The purpose of the research was to better understand real-world fuel consumption and vehicle exhaust emissions from the New Zealand fleet and use this knowledge to improve the ability of the Transport Agency’s Vehicle Emissions Prediction Model (VEPM) to predict actual emissions. 

A portable emissions monitoring system (PEMS) was developed to measure real-world emissions from a range of typical New Zealand vehicles on a route typical of New Zealand conditions. Testing was undertaken in Auckland between January and May 2018 on six light duty petrol vehicles, 20 light duty diesel vehicles and six heavy duty diesel vehicles, including New Zealand-new and Japanese-used imported vehicles manufactured between 1996 and 2014. 

As expected, our testing found that real-world emissions of most pollutants were higher than regulated standards (up to eight times). The real-world NOX results were comparable to real-world emissions from Europe and Australia for similar vehicles.

Although based on real-world factors, VEPM emissions factors were found to be different from those derived from the PEMS results in this study for all vehicles tested and all speed bins analysed. 

Recommendations have been made to improve and update VEPM utilising the results of this study and other international and New Zealand evidence. Additional testing of heavy duty diesel vehicles is recommended to better predict emissions and fuel consumption from this class of vehicles.

Keywords: exhaust emissions, fuel consumption, PEMS testing, real-world driving