http://orcid.org/0000-0002-7107-7086
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ABSTRACT
This study presents a comparison of fleet average emission factor (s) derived from a traffic emission model with EFs estimated using plume-based measurements, including an investigation of the contribution of vehicle classes to carbon monoxide (CO), nitrogen oxides (NOx), and elemental carbon (EC) along an urban corridor. To this end, a field campaign was conducted over one week in June 2016 on an arterial road in Toronto, Canada. Traffic data were collected using a traffic camera and a radar, whereas air quality was characterized using two monitoring stations: one located at ground level and another at the rooftop of a four-story building. A traffic simulation model was calibrated and validated, and second-by-second speed profiles for all vehicle trajectories were extracted to model emissions. In addition, dispersion modeling was conducted to identify the extent to which differences in emissions translate to differences in near-road concentrations. The results indicate that modeled EFs for CO and NOx are twice as high as plume-based EFs. Besides, modeled results indicate that transit bus emissions accounted for 60% and 70% of the total emissions of NOx and EC, respectively. Transit bus emission rates in g/passenger·km for NOx and EC were up to 8 and 22 times, respectively, the emission rates of passenger cars. In contrast, the Toronto streetcars, which are electrically fueled, were found to improve near-road air quality despite their negative impact on traffic speeds. Finally, we observe that the difference in estimated concentrations derived from the two methods is not as large as the difference in estimated emissions due to the influence of meteorology and of the urban background given that the study network is located in a busy downtown area.
Implications: This study presents a comparison of fleet average emission factor (s) derived from a traffic emission model with EFs estimated using plume-based measurements, including an investigation of the contribution of vehicle classes to various pollutants. Besides, dispersion modeling was conducted to identify the extent to which differences in emissions translate to differences in near-road concentrations. It was observed that the difference in estimated concentrations derived from the two methods is not as large as the difference in estimated emissions due to the influence of meteorology and of the urban background, as the study network is located in a busy downtown area.
Supplementary Material
Supplemental data for this paper can be accessed on the publisher’s website.
Additional information
Notes on contributors
Junshi Xu
Junshi Xu is a Ph.D. candidate in the Department of Civil & Mineral Engineering at the University of Toronto.
Jonathan Wang
Jonathan Wang and Nathan Hilker are Ph.D. candidates in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto.
Masoud Fallah-Shorshani
Masoud Fallah-Shorshani is a Post-doctoral fellow in the Department of Civil & Mineral Engineering at the University of Toronto.
Marc Saleh
Marc Saleh is a M.Sc. candidate in the Department of Civil & Mineral Engineering at the University of Toronto.
Ran Tu
Marc Saleh is a M.Sc. candidate in the Department of Civil & Mineral Engineering at the University of Toronto.
Christos Stogios
Ran Tu, An Wang and Laura Minet are Ph.D. candidates in the Department of Civil & Mineral Engineering at the University of Toronto.
Greg Evans
Christos Stogios is a M.Sc. graduate from the Department of Civil & Mineral Engineering at the University of Toronto.
Marianne Hatzopoulou
Greg Evans is a professor in the Department of Chemical Engineering and Applied Chemistry at the University of Toronto. He is the director of the Southern Ontario Center for Atmospheric Aerosol Research (SOCAAR), which is an interdisciplinary centre for the study of air quality, with a focus on how aerosols impact human health and the environment.
Marianne Hatzopoulou is an associate professor in the Department of Civil & Mineral Engineering at the University of Toronto. Her research area bridges between transportation and environmental analysis; and her main expertise is in modelling of road transport emissions and urban air quality as well as evaluating population exposure to air pollution. She is a Canada Research Chair in Transportation and Air Quality, and leads the Transportation and Air Quality (TRAQ) research group.
