Role of Vehicular Emissions in Urban Air Quality: The Covid-19 Lockdown Experiment

While the decrease in air pollutants concentration during the COVID-19 lockdown is well documented, high-resolution and multi-city data have not yet been explored systematically to derive a generalizable quantitative link to the drop in vehicular traffic. To bridge this gap, high spatial resolution air quality and geo-referenced traffic datasets were compiled for the city of London during three weeks with significant differences in traffic. The London analysis was then augmented with a meta-analysis of lower-resolution studies from 12 other cities. The results confirm that the improvement in air quality can be partially directly attributed to the drop of traffic density, and more importantly quantifies the elasticity (0.71_NO2 & 0.56_PM2.5 ) of their linkages to elucidate the contribution of vehicular emissions to adverse air quality in cities. The findings can be used to project the positive impacts on urban air quality of the ongoing shift to electric vehicles and micro-mobility.