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Estimating vehicle emissions-The need for a better approach

Roger Barrowcliffe

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Vehicle emissions – what we know and what we do currently….Measurements tell us that NOx emissions depend

principally on engine load, ie accelerationMicrosimulation models provide a viable means of

modelling instantaneous emissions

For assessment of air quality we use:outputs from traffic models, ie volume and speeddispersion models with an averaging time of one

hour

Clear Air Thinking

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COPERT Emission Factors (results taken from TfL measurements)

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Instantaneous NOx emissions(results taken from Emissions Analytics)

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NOx emission by Flow State(Joumard et al 2008)

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Dutch Approach to Emission Factorsemission factors 2016 [g/km] Euro-6 RDE Euro-5urban congestion NOx 0.679 0.314 1.000

NO2 0.288 0.129 0.327urban normal NOx 0.571 0.244 0.708

NO2 0.225 0.100 0.214urban free flow NOx 0.454 0.188 0.542

NO2 0.176 0.077 0.160rural NOx 0.397 0.170 0.531

NO2 0.157 0.070 0.161motorway average NOx 0.404 0.171 0.588

NO2 0.165 0.070 0.181motorway congestion NOx 0.594 0.253 0.746

NO2 0.233 0.104 0.227motorway strict 80 km/h speed limit NOx 0.310 0.127 0.405

NO2 0.122 0.052 0.122motorway no strict 80 km/h speed limit NOx 0.312 0.185 0.466

NO2 0.095 0.046 0.152motorway strict 100 km/h speed limit NOx 0.253 0.139 0.501

NO2 0.111 0.057 0.158motorway no strict 100 km/h speed limit NOx 0.294 0.148 0.528

NO2 0.127 0.061 0.165motorway 120 km/h speed limit NOx 0.377 0.166 0.576

NO2 0.156 0.068 0.178motorway 130 km/h speed limit NOx 0.434 0.173 0.589

NO2 0.174 0.071 0.181

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So, is there a better way of estimating vehicle emission for use in dispersion models?