NO2 Emissions at Highway Toll Stations: Integrated Satellite and Traffic Data Insights from Holiday Analysis

Abstract

Nitrogen dioxide (NO₂), a significant urban pollutant, is a primary component of vehicular emissions that impacts air quality around highway infrastructure. Effective monitoring of NO₂ near toll stations is essential for advancing sustainable transportation and air quality management. This study leverages data from the TROPOMI instrument aboard the Sentinel-5P satellite to observe NO₂ distribution at five highway toll stations in Zhejiang Province, China, from January 2019 to June 2023, focusing on the effects of traffic volume changes during statutory holidays. Key findings include: (1) During toll-free holidays, traffic volume surges by 49% while NO₂ concentrations at toll stations decrease by up to 21%. This suggests that reduced vehicle wait times help mitigate emissions, particularly when toll gates are open to allow smoother traffic flow. (2) In economically developed cities, prolonged vehicle queuing and idling increased NO₂ emissions at toll stations by approximately 15–28%, emphasizing the need for effective congestion management to control emissions. (3) During the COVID-19 pandemic, preventive measures such as disinfection and health checks extend waiting times at toll stations, causing NO₂ levels to rise by up to 35% even with an overall decrease in traffic volume. By integrating satellite data with traffic flow information, this study highlights the potential of optimized toll station infrastructure to reduce NO₂ emissions and improve urban air quality, especially during peak traffic. These insights provide actionable recommendations for sustainable highway infrastructure management and air quality improvement.