Development of an Air Pollution Impact Assessment Tool for Emission Reduction in Bus Fleets


Student thesis: Doctoral Thesis

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Award date2 Apr 2020


Street air pollution is an important issue in Hong Kong due to its poor quality. Insufficient street ventilation coupled with high vehicle emissions is the common cause of this problem (i.e., elevated pollutant concentrations). On-road emissions account for more than 9% of Respirable Suspended Particulates (RSP) and 18% of Nitrogen Oxides (NOX) emissions of overall Hong Kong emissions. Minimizing the overall roadside emissions from the existing bus fleet would be an important policy instrument for tackling local air quality. In this study, a new ArcGIS-based impact assessment tool coupled with Monte Carlo optimization was developed. The function of the tool is to evaluate the Relative Health Impacts (RHI) associated with different fleet arrangements. Moreover, it provides an optimal solution for bus fleet management. The tool takes into consideration the types of franchised bus, service frequency, travel distance, passenger occupancy, local topology, street ventilation, and exposure population. Overall, up to 15% of potential improvement from diesel bus-related air quality (i.e., RHI) can be achieved by rearranging bus fleet services. To better understand the effects of different bus policies on local air quality, the tool was also applied to the scenarios of Low Emission Zone (LEZ), and Sha Tin to Central Link (SCL). Comparing to business as usual scenario, the LEZ scenario can lead to a 7.5 % and 3.9% reduction on RSP and NOX, respectively. In the SCL scenario, a 3.2% increment reduction of RSP can be achieved.