Emission Factors for Estimating Motor Vehicle Particle Emissions in Urban Areas
Estimating the levels and spatial distribution of particle emissions emitted from motor vehicles in urban areas is a very complex problem. This stems from the fact that there are a multiplicity of factors that can influence emission levels, ranging from fleet composition, to road type, vehicle speed, fuel used, load and operating conditions, and environmental factors. One approach that can be employed is to combine scientifically-based emission factor values with transport modelling. However, the current state of knowledge is that there are numerous emission factors published in the literature for different types of measurements and for different road environments around the world, but it is unclear which emission factors are most suitable to use in combination with transport modelling.
We examined over 900 published emission factors derived for particle emissions from motor vehicles relating to a range of different vehicle types, fleet compositions, fuels, traffic and road environments around the world. These emission factors were estimated using different methods, ranging from dynamometer studies conducted in laboratories, to roadside and in-tunnel measurements. Emission factors examined related to particle number, surface area, mass and volume size distributions.
Statistical analysis was used to determine the applicability and sensitivity of these emission factors to accurately represent vehicle emissions; and sensitivity analysis was used to identify what results the different emission factors produce. These approaches assisted in determining the final set of emission factors considered suitable to model motor vehicle emissions, in combination with transport modelling.
The study enabled recommendations to be made regarding suitable emission factors to use in transport modelling, not only for the South East Queensland region, Australia, but which have application for use in other regions, particularly where there may be limited or no suitable measurements or data available to develop motor vehicle inventories.