Microsimulation-Based Emissions Modeling for a Major Infrastructure Renewal Plan: Assessment of Network Attributes and Land Use Effects on Vehicular Emissions

This study demonstrated a comprehensive microsimulation-based emissions modeling framework for a 15.37-km-long road network in the downtown core of Halifax, Canada. The study developed a sequential microscopic traffic simulation and emissions modeling tool to estimate vehicular emissions at a finer-grain spatial resolution using instantaneous speed profiles. The study evaluated the effects of a major infrastructure renewal plan that focuses on rebuilding part of the expressway in the downtown core (e.g., the replacement of multigrade signalized intersections at the Cogswell interchange with roundabouts and associated improvements). Emissions were estimated for six major criteria pollutants, including greenhouse gas (GHG), carbon monoxide (CO), nitrogen oxides (NO_x), sulfur dioxide (SO₂), particulate matter with a diameter of 10 µm or less (PM-10), and particulate matter with a diameter of 2.5 µm or less (PM-2.5). The results showed significant changes in emission patterns caused by the infrastructure renewal plan. The study evaluated the sensitivity of different traffic attributes as well as their combined effect on emissions’ variation. The results revealed that the plan increased emissions (from 4.246% to 28.571%) in the entire network. However, area-level evaluation suggested a reduction in emissions (from 0.018% to 19.855%) in the roundabout area compared with the multigrade signalized intersections. A land use regression model was also developed to examine the potential effect of land use and built environment attributes on emissions. The microscopic emissions model’s results will assist transportation planners in considering strategies to mitigate air pollution in the final design and implementation of the infrastructure renewal plan.