“…Actual information, such as emission standards (from EURO-III to EURO-VI), and additional mitigation measures (e.g., diesel particulate filter) fitted at the tailpipe for each vehicle are very difficult (if not impossible) to obtain during routine monitoring. Some studies adopted a vehicular emission model (e.g., Mobile 6 and COPERT4) to better mimic the variation in road traffic emissions and then to feed the information into an air dispersion model, including a CFD model [39][40][41]. However, this kind of model requires many inputs, such as fuel consumption, fleet configuration, trip length, distribution of vehicle miles traveled by road types, average speed distribution by road types, annual mileage, which are not available in many areas/countries; thus, large uncertainty in the simulated traffic emissions and, in turn, the air quality simulations results.…”