A bottom-up modelling chain to evaluate the impact of urban road transport policies on air quality and human health

A 4-module modelling chain for assessing urban traffic emissions' impacts on air quality and human health is presented. The first module simulates the traffic flows for the urban road network, separately considering private and public transport; the second performs a bottom-up assessment of road traffic emissions, including non-exhaust components and dust resuspension; the third uses a Eulerian Chemistry and Transport Model for regional and urban scale air quality simulation, combining traffic emissions with all the other anthropogenic and natural emissions. Lastly, the fourth module assesses the effects of air quality on human health based on the latest WHO-recommended Concentration Response Functions for mortality. As test case, the modelling chain was applied to the city of Milan (Italy). The added value of the modelling chain is evaluated by comparing the simulation results for NO2 and particulate matter ambient concentrations with those obtained with the classic top-down approach and with observed data. Simulation results show improvements in the accuracy of model predictions over the urban area and highlight the importance of properly accounting for dust resuspension in traffic policy evaluations because of its increasing contribution to PM10 traffic emissions in the future.