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• 1. [Article] Effect of Reducing Maximum Cycle Length on Roadside Air Quality and Travel Times on a Corridor in Portland, OR

  The Sydney Coordinated Adaptive Traffic System (SCATS), an adaptive signal system designed to reduce congestion, has been installed on a heavily trafficked roadway in Portland, OR. In addition to traffic ...

  Citation × Citation Citation Abstract Copy Title: Effect of Reducing Maximum Cycle Length on Roadside Air Quality and Travel Times on a Corridor in Portland, OR Author: Kendrick, Christine M., Urowsky, David, Rotich, Willie, Koonce, Peter, George, Linda Acha Year: 2014 The Sydney Coordinated Adaptive Traffic System (SCATS), an adaptive signal system designed to reduce congestion, has been installed on a heavily trafficked roadway in Portland, OR. In addition to traffic performance metrics, we are investigating how this system affects roadway emissions of air pollutants. A twenty-second reduction to maximum cycle length was proposed for the SCATS system to address pedestrian delay concerns. A two-week trial period with this reduced cycle length was implemented. Travel times and roadside air pollution concentrations were monitored throughout this study period and compared to before and after periods with the current maximum cycle length. Average travel times were found to be significantly higher during the reduced maximum cycle length, but with a mean difference of only 4-5 seconds for travel time. Assessment of travel time for this roadway suggests that a twenty second decrease in maximum cycle length to help shorten pedestrian delay can be made without significant consequences to travel time. Total traffic volumes were consistent for all four weeks of the study. Meteorological conditions were similar for the first two weeks comparing maximum cycle lengths. A shift in ambient temperature led the second two weeks of the cycle length comparison to have more similar meteorological conditions versus the first two weeks. Average NO and NO2 concentrations were not significantly different for the first half of the study. However, NO and NO2 concentrations were significantly higher during the reduced maximum cycle length for the second half of the study. When there was a significant difference based on t-test statistics, the measurements did show an increase in roadside concentrations during the shorter maximum cycle length. Preliminary results are unclear if changes to air quality (as assessed by NO and NO2 concentrations) occur or not due to the reduced maximum cycle length. Results require further comparative analysis in which meteorology and traffic conditions are controlled for so that any difference in air quality due to maximum cycle length alone can be quantified. Title: Effect of Reducing Maximum Cycle Length on Roadside Air Quality and Travel Times on a Corridor in Portland, OR Author: Kendrick, Christine M., Urowsky, David, Rotich, Willie, Koonce, Peter, George, Linda Acha Year: 2014 The Sydney Coordinated Adaptive Traffic System (SCATS), an adaptive signal system designed to reduce congestion, has been installed on a heavily trafficked roadway in Portland, OR. In addition to traffic performance metrics, we are investigating how this system affects roadway emissions of air pollutants. A twenty-second reduction to maximum cycle length was proposed for the SCATS system to address pedestrian delay concerns. A two-week trial period with this reduced cycle length was implemented. Travel times and roadside air pollution concentrations were monitored throughout this study period and compared to before and after periods with the current maximum cycle length. Average travel times were found to be significantly higher during the reduced maximum cycle length, but with a mean difference of only 4-5 seconds for travel time. Assessment of travel time for this roadway suggests that a twenty second decrease in maximum cycle length to help shorten pedestrian delay can be made without significant consequences to travel time. Total traffic volumes were consistent for all four weeks of the study. Meteorological conditions were similar for the first two weeks comparing maximum cycle lengths. A shift in ambient temperature led the second two weeks of the cycle length comparison to have more similar meteorological conditions versus the first two weeks. Average NO and NO2 concentrations were not significantly different for the first half of the study. However, NO and NO2 concentrations were significantly higher during the reduced maximum cycle length for the second half of the study. When there was a significant difference based on t-test statistics, the measurements did show an increase in roadside concentrations during the shorter maximum cycle length. Preliminary results are unclear if changes to air quality (as assessed by NO and NO2 concentrations) occur or not due to the reduced maximum cycle length. Results require further comparative analysis in which meteorology and traffic conditions are controlled for so that any difference in air quality due to maximum cycle length alone can be quantified. Close

• 2. [Article] Diurnal and Seasonal Variations of NO, NO2 and PM2.5 Mass as a Function of Traffic Volumes Alongside an Urban Arterial

  Urban arterial corridors are landscapes that give rise to short and long-term exposures to transportation-related pollution. With high traffic volumes and a wide mix of road users, urban arterial environments ...

  Citation × Citation Citation Abstract Copy Title: Diurnal and Seasonal Variations of NO, NO2 and PM2.5 Mass as a Function of Traffic Volumes Alongside an Urban Arterial Author: Kendrick, Christine M., Koonce, Peter, George, Linda A. Year: 2015 Urban arterial corridors are landscapes that give rise to short and long-term exposures to transportation-related pollution. With high traffic volumes and a wide mix of road users, urban arterial environments are important targets for improved exposure assessment to traffic-related pollution. A common method to estimate exposure is to use traffic volumes as a proxy. The study presented here analyzes a unique yearlong dataset of simultaneous roadside air quality and traffic observations for a U.S. arterial to assess the reliability of using traffic volumes as a proxy for traffic-related exposure. Results show how the relationships of traffic volumes with NO and NO2 vary not only by time of day and season but also by time aggregation. At short-term aggregations (15 minutes) nitrogen oxides were found to have a significant linear relationship with traffic volumes during morning hours for all seasons although variability was still high (r2= 0.1 - 0.45 NO, r2=0.14 - 0.27 NO2), and little to no relationship during evening periods (r222). Comparisons with coarse annual results validate the use of traffic volumes to estimate annual exposure concentrations for morning periods (r2= 0.89 NO, r2=0.87 NO2) and evening NO2 (r2=0.46). Traffic volumes are a weak or poor predictor for annual evening NO (r2= -0.09) and short-term 15 minute aggregations. Seasonal and diurnal characterizations show that roadside PM2.5 (mass) measurements do not have a relationship with local traffic volumes, leading us to conclude that PM2.5 mass is more tied to regional sources and meteorological conditions. As epidemiology and personal exposure assessment research aims to study health impacts and pollutant levels encountered by pedestrians, bicyclists, those waiting for transit, and other road users, these results show when traffic volumes alone can be a reliable proxy for exposure and when this approach is not warranted. Title: Diurnal and Seasonal Variations of NO, NO2 and PM2.5 Mass as a Function of Traffic Volumes Alongside an Urban Arterial Author: Kendrick, Christine M., Koonce, Peter, George, Linda A. Year: 2015 Urban arterial corridors are landscapes that give rise to short and long-term exposures to transportation-related pollution. With high traffic volumes and a wide mix of road users, urban arterial environments are important targets for improved exposure assessment to traffic-related pollution. A common method to estimate exposure is to use traffic volumes as a proxy. The study presented here analyzes a unique yearlong dataset of simultaneous roadside air quality and traffic observations for a U.S. arterial to assess the reliability of using traffic volumes as a proxy for traffic-related exposure. Results show how the relationships of traffic volumes with NO and NO2 vary not only by time of day and season but also by time aggregation. At short-term aggregations (15 minutes) nitrogen oxides were found to have a significant linear relationship with traffic volumes during morning hours for all seasons although variability was still high (r2= 0.1 - 0.45 NO, r2=0.14 - 0.27 NO2), and little to no relationship during evening periods (r222). Comparisons with coarse annual results validate the use of traffic volumes to estimate annual exposure concentrations for morning periods (r2= 0.89 NO, r2=0.87 NO2) and evening NO2 (r2=0.46). Traffic volumes are a weak or poor predictor for annual evening NO (r2= -0.09) and short-term 15 minute aggregations. Seasonal and diurnal characterizations show that roadside PM2.5 (mass) measurements do not have a relationship with local traffic volumes, leading us to conclude that PM2.5 mass is more tied to regional sources and meteorological conditions. As epidemiology and personal exposure assessment research aims to study health impacts and pollutant levels encountered by pedestrians, bicyclists, those waiting for transit, and other road users, these results show when traffic volumes alone can be a reliable proxy for exposure and when this approach is not warranted. Close