Impact of Traffic Signal Timing on Sidewalk-Level Particulate Matter Concentrations

Abstract

Improving the efficiency of urban traffic operations along arterials is a priority for many agencies because congestion affects the movement of people and goods in many cities. Advanced traffic management systems are being implemented to optimize traffic signal timing in congested corridors. Pedestrians and transit users are even more exposed to vehicle emissions than are drivers. However, pedestrian exposure to traffic emissions is typically not a consideration when traffic signal timing decisions are made. The relationship between exposure to air pollution and traffic signal timing has not yet been fully explored or modeled. This paper quantifies the factors that contribute to concentrations of sidewalk-level particulate matter (1.0 to 2.5 μm in diameter) at a busy intersection along an urban arterial in Portland, Oregon. The study is the first research effort to combine real-world, detailed traffic signal timing data (at 5-s intervals) and air pollutant concentration data. Several types of variables are included in the statistical analysis: traffic signal timing variables, weather-related variables, traffic volume and composition variables, and variables associated with bus presence and characteristics. Statistical results show the importance of signal timing variables, traffic volumes, and queuing.