Impact of COVID-19 Mobility Changes on Air Quality in Warsaw

Featured Application The article describes the results of a project that concerned the creation of a method of using big data to build traffic models in special periods (e.g., during a pandemic) when obtaining data in a traditional way is difficult or not possible. Then, based on the comparison between those models and the typical state of the transport system, it is possible to perform comparative analysis and impact analyses. For example, analyses of social cost related to travel restrictions can be estimated. During a pandemic, the mobility of people changes significantly from the normal situation (the number of trips made, the directions of travel and the modes of transport used). Changes in mobility depend on the scale of the pandemic threat and the scale of the restrictions introduced and assessing the impact of these changes is not straightforward. This raises the question of the social cost of changes in mobility and their impact on the environment, including air quality. The article shows that it is possible to determine this impact using big data from mobile operators'-SIM card movements and data from air quality monitoring stations. Data on SIM card movements allows for reconstructing the state of the transport system before and during the different phases of a pandemic. The changes in mobility of people determined in this way can be related to the results of measurements of pollutant concentrations in the air. In this way, it is possible to identify links between mobility changes and air quality. The article presents the extent (in relation to the state without the pandemic) of changes in the mobility of the population during the pandemic and the related impact on air quality using the example of Warsaw.