A decade of measuring on-road vehicle emissions with remote sensing in Australia

Abstract

A remote sensing device (RSD) has been used at 23 locations across in Western Australia (20) and Queensland (3) in the period 2009–2019, generating more than 100,000 valid emission samples over more than a decade. After a statistical assessment of similarity and bias correction, the data were combined for this study to assess the performance of the light-duty vehicle (LDV) on-road fleet, i.e. cars, sport utility vehicles (SUVs) and light-commercial vehicles (LCVs). The percentage of excessive emitters is estimated to be about 2%. Diesel LDVs generally show stabilising or even increasing NOx-to-CO2 ratios with respect to progressive Euro classes. The RSD data confirm that the NOx emission issues with diesel vehicles in Europe are similarly observed in vehicles sampled in Western Australia and Queensland.There is insufficient empirical evidence for a consistent reduction in real-world PM (‘soot’) emissions over progressive emission standards for diesel LDVs, after adjusting for the effect of vehicle age. Further analysis of Euro 5 diesel LDVs shows substantial differences between vehicle types. The diesel LCV and SUV mean smoke factors (Euro 5) are 141% and 64% higher than diesel passenger cars.On average, across 1–5 years of vehicle age, 4% of the measured Euro 5 diesel cars have smoke factor values that suggest diesel particulate filters (DPFs) are malfunctioning, potentially modified or are not present. The percentages are higher for SUVs and LCVs, i.e. 7% and 12%, respectively. Pooled data for the two most recent years of manufacture (2017–2018) suggest that 1% of one-two year old diesel SUVs and 2% of one-two year old diesel LCVs have DPF issues, i.e. malfunctioning or potentially modified DPFs. These percentages are high when compared with a similar study conducted in the UK. The percentage of potentially malfunctioning or lack of DPFs in Euro 5 diesel LDVs shows a statistically significant trend (p < 0.05) and increases strongly with vehicle age in a non-linear fashion. This is in line with an increase in the number of smoky vehicles that were reported in the period 2015–2019, in particular for diesel vehicles.