Traffic flow pattern and meteorology at two distinct urban junctions with impacts on air quality

Traffic during operation at a junction undergoes different flow conditions and modal events which result into dynamic fleet characteristics generating more emissions and stronger vehicle-induced heat and wakes generating obscure dispersion. Traffic in a manner operated at junctions often creates pockets of higher concentrations the locations of which shift as a result of the combine effects of traffic dynamics and random airflow. This research examined the impacts of traffic dynamics and meteorology on the levels and locations of higher concentrations of pollutant CO, NO2 and PM within the influence of signalized traffic intersection and a conventional two-lane roundabout in a response to varying flow conditions and emissions resulted from the traffic operations. Three line source dispersion models have been used to determine the impact on air quality. Emissions have been calculated for different scenarios developed from different combinations of semi-empirical and field based time and space-mean speeds and lane-width based density when traffic undergoes free, interrupted and congested-flow conditions during operation. It has been found that the locations of highest concentrations within the domain change as traffic with different modal share encounters different flow conditions at different times of a day.

► Traffic flow of mixed modal share generates dissimilar road density with time.
► Scale of pollutant dispersion depends upon different traffic flow conditions.
► Spatial distribution of concentrations changes with the traffic flow pattern.
► Level and location of peak concentration changes with different states of congestion.