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Papers by William Farrell

Research paper thumbnail of Characterizing the impact of traffic and the built environment on near-road ultrafine particle and black carbon concentrations

Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardio... more Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardiorespiratory morbidity. We examined the relationship between near road UFPs and several traffic and built environment factors to identify predictors that may be used to estimate exposures in population-based studies. Black carbon (BC) was also examined. Methods: Data were collected on up to 6 occasions at 73 sites in Montreal, Canada over 6-week period during summer, 2012. After excluding highly correlated variables, road width, truck ratio (trucks/total traffic), building height, land zoning parameters, and meteorological factors were evaluated. Randomeffect models were used to estimate percent changes in UFP and BC concentrations with interquartile changes in each candidate predictor adjusted for meteorological factors. Results: Mean pollutant concentrations varied substantially across sites (UFP range: 1977-94, 798 particles/cm 3 ; BC range: 29-9460 ng/m 3 ). After adjusting for meteorology, interquartile increases in road width (14%, 95% CI: 0, 30), building height (13%, 95% CI: 5, 22), and truck ratio (13%, 95% CI: 3, 23) were the most important predictors of mean UFP concentrations. Road width (28%, 95% CI: 9, 51) and industrial zoning (18%, 95% CI: 2, 37) were the strongest predictors of maximum UFP concentrations. Industrial zoning (35%, 95% CI: 9, 67) was the strongest predictor of BC. Conclusions: A number of traffic and built environmental factors were identified as important predictors of near road UFP and BC concentrations. Exposure models incorporating these factors may be useful in evaluating the health effects of traffic related air pollution. Crown

Research paper thumbnail of Characterizing the impact of traffic and the built environment on near-road ultrafine particle and black carbon concentrations

Environmental Research, 2014

Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardio... more Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardiorespiratory morbidity. We examined the relationship between near road UFPs and several traffic and built environment factors to identify predictors that may be used to estimate exposures in population-based studies. Black carbon (BC) was also examined. Methods: Data were collected on up to 6 occasions at 73 sites in Montreal, Canada over 6-week period during summer, 2012. After excluding highly correlated variables, road width, truck ratio (trucks/total traffic), building height, land zoning parameters, and meteorological factors were evaluated. Randomeffect models were used to estimate percent changes in UFP and BC concentrations with interquartile changes in each candidate predictor adjusted for meteorological factors. Results: Mean pollutant concentrations varied substantially across sites (UFP range: 1977-94, 798 particles/cm 3 ; BC range: 29-9460 ng/m 3 ). After adjusting for meteorology, interquartile increases in road width (14%, 95% CI: 0, 30), building height (13%, 95% CI: 5, 22), and truck ratio (13%, 95% CI: 3, 23) were the most important predictors of mean UFP concentrations. Road width (28%, 95% CI: 9, 51) and industrial zoning (18%, 95% CI: 2, 37) were the strongest predictors of maximum UFP concentrations. Industrial zoning (35%, 95% CI: 9, 67) was the strongest predictor of BC. Conclusions: A number of traffic and built environmental factors were identified as important predictors of near road UFP and BC concentrations. Exposure models incorporating these factors may be useful in evaluating the health effects of traffic related air pollution. Crown

Research paper thumbnail of Evaluating vehicular emissions with an integrated mesoscopic and microscopic traffic simulation

Canadian Journal of Civil Engineering, 2014

This paper demonstrates the implementation of a traffic simulation linked with instantaneous emis... more This paper demonstrates the implementation of a traffic simulation linked with instantaneous emissions modelling and is used to evaluate the effects of street closures and area-wide pedestrianization on vehicle-induced greenhouse gas emissions. The study is set in Montreal, Canada where traffic in a dense borough (8656 links) is simulated in a dynamic traffic assignment mode to generate second-by-second speed profiles along every link in the 7-8 AM period. Instantaneous speeds are then used to estimate link-level and intersection-level emissions. The traffic demand at the borough boundaries is simulated using a mesoscopic traffic assignment model developed for the Montreal metropolitan region (127 217 links). Street closures and area-wide pedestrianization schemes are modelled within the microscopic as well as the mesoscopic models to evaluate their effects on greenhouse gas emissions, both while accounting for changes in demand and under constant demand. In all cases, we observe an increase in borough-level greenhouse gas emissions compared to the base-case scenario indicating that such schemes do not lead to a reduction in emissions even when accounting for changes in demand. We also compare emissions calculated using the microscopic models (traffic and emissions) and those obtained from the mesoscopic assignment (traffic and average-speed emissions) and observe that the regional model is much less sensitive to local-level changes mostly due to the incapacity of simulating accelerations and decelerations and therefore underestimating the changes in borough-level emissions compared to the base-case scenario. This indicates the importance of adopting instantaneous emissions models for the evaluation of changes to street configuration.

Research paper thumbnail of Characterizing the impact of traffic and the built environment on near-road ultrafine particle and black carbon concentrations

Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardio... more Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardiorespiratory morbidity. We examined the relationship between near road UFPs and several traffic and built environment factors to identify predictors that may be used to estimate exposures in population-based studies. Black carbon (BC) was also examined. Methods: Data were collected on up to 6 occasions at 73 sites in Montreal, Canada over 6-week period during summer, 2012. After excluding highly correlated variables, road width, truck ratio (trucks/total traffic), building height, land zoning parameters, and meteorological factors were evaluated. Randomeffect models were used to estimate percent changes in UFP and BC concentrations with interquartile changes in each candidate predictor adjusted for meteorological factors. Results: Mean pollutant concentrations varied substantially across sites (UFP range: 1977-94, 798 particles/cm 3 ; BC range: 29-9460 ng/m 3 ). After adjusting for meteorology, interquartile increases in road width (14%, 95% CI: 0, 30), building height (13%, 95% CI: 5, 22), and truck ratio (13%, 95% CI: 3, 23) were the most important predictors of mean UFP concentrations. Road width (28%, 95% CI: 9, 51) and industrial zoning (18%, 95% CI: 2, 37) were the strongest predictors of maximum UFP concentrations. Industrial zoning (35%, 95% CI: 9, 67) was the strongest predictor of BC. Conclusions: A number of traffic and built environmental factors were identified as important predictors of near road UFP and BC concentrations. Exposure models incorporating these factors may be useful in evaluating the health effects of traffic related air pollution. Crown

Research paper thumbnail of Characterizing the impact of traffic and the built environment on near-road ultrafine particle and black carbon concentrations

Environmental Research, 2014

Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardio... more Background: Increasing evidence suggests that ultrafine particles (UFPs) may contribute to cardiorespiratory morbidity. We examined the relationship between near road UFPs and several traffic and built environment factors to identify predictors that may be used to estimate exposures in population-based studies. Black carbon (BC) was also examined. Methods: Data were collected on up to 6 occasions at 73 sites in Montreal, Canada over 6-week period during summer, 2012. After excluding highly correlated variables, road width, truck ratio (trucks/total traffic), building height, land zoning parameters, and meteorological factors were evaluated. Randomeffect models were used to estimate percent changes in UFP and BC concentrations with interquartile changes in each candidate predictor adjusted for meteorological factors. Results: Mean pollutant concentrations varied substantially across sites (UFP range: 1977-94, 798 particles/cm 3 ; BC range: 29-9460 ng/m 3 ). After adjusting for meteorology, interquartile increases in road width (14%, 95% CI: 0, 30), building height (13%, 95% CI: 5, 22), and truck ratio (13%, 95% CI: 3, 23) were the most important predictors of mean UFP concentrations. Road width (28%, 95% CI: 9, 51) and industrial zoning (18%, 95% CI: 2, 37) were the strongest predictors of maximum UFP concentrations. Industrial zoning (35%, 95% CI: 9, 67) was the strongest predictor of BC. Conclusions: A number of traffic and built environmental factors were identified as important predictors of near road UFP and BC concentrations. Exposure models incorporating these factors may be useful in evaluating the health effects of traffic related air pollution. Crown

Research paper thumbnail of Evaluating vehicular emissions with an integrated mesoscopic and microscopic traffic simulation

Canadian Journal of Civil Engineering, 2014

This paper demonstrates the implementation of a traffic simulation linked with instantaneous emis... more This paper demonstrates the implementation of a traffic simulation linked with instantaneous emissions modelling and is used to evaluate the effects of street closures and area-wide pedestrianization on vehicle-induced greenhouse gas emissions. The study is set in Montreal, Canada where traffic in a dense borough (8656 links) is simulated in a dynamic traffic assignment mode to generate second-by-second speed profiles along every link in the 7-8 AM period. Instantaneous speeds are then used to estimate link-level and intersection-level emissions. The traffic demand at the borough boundaries is simulated using a mesoscopic traffic assignment model developed for the Montreal metropolitan region (127 217 links). Street closures and area-wide pedestrianization schemes are modelled within the microscopic as well as the mesoscopic models to evaluate their effects on greenhouse gas emissions, both while accounting for changes in demand and under constant demand. In all cases, we observe an increase in borough-level greenhouse gas emissions compared to the base-case scenario indicating that such schemes do not lead to a reduction in emissions even when accounting for changes in demand. We also compare emissions calculated using the microscopic models (traffic and emissions) and those obtained from the mesoscopic assignment (traffic and average-speed emissions) and observe that the regional model is much less sensitive to local-level changes mostly due to the incapacity of simulating accelerations and decelerations and therefore underestimating the changes in borough-level emissions compared to the base-case scenario. This indicates the importance of adopting instantaneous emissions models for the evaluation of changes to street configuration.