New Approaches For Understanding Vehicle Emissions Using Remote Sensing

Despite improvements in technology and increasingly strict legislation, road transport remains a key source of air quality pollutants. Accurate emission estimates are important for informing policy to combat the deleterious effects of exhaust species on human health. A key advantage of vehicle emission remote sensing is it can rapidly measure and characterise hundreds of thousands of vehicles. However, to fully realise the potential of remote sensing and gain a comprehensive assessment of emissions, new developments in calculating emission factors are needed. A recurring theme of this thesis is the calculation of emission-engine power models, which allow remote sensing to be used to address more facets of vehicle emissions than it is typically able. A method is developed to calculate distance-specific emission factors, which is validated using portable emission measurement system data. Distance-specific emissions can be compared with other measurement techniques and legislation, and can be used in emission inventory development. A remote sensing-based inventory is directly compared to the UK National Atmospheric Emissions Inventory, achieving excellent carbon balance (within 1%) but revealing that NOx emissions may be being under-reported by up to 32% at a national level. Remote sensing data are also combined with a large driving activity database to address the effects of driver behaviour and challenge the COPERT approach for emission factor calculation. A robust statistical framework is used to assess emission deterioration, and it is shown that older gasoline cars show a skewed rate of deterioration whereas modern gasoline and diesel emissions are well controlled. A key conclusion is the importance of the differences between manufacturers, which are significant for individual vehicles, for emission deterioration, and in inventory development. This analysis shows that accounting for manufacturers in inventory calculations results in a 13.4% range in total NOx emissions, an influence not currently reflected in European emission inventories.