sustainability Article The Impact of the COVID-19 Emergency on Local Vehicular Traffic and Its Consequences for the Environment: The Case of the City of Reggio Emilia (Italy) Samuele Marinello 1,* , Francesco Lolli 1,2 and Rita Gamberini 1,2 1 En&Tech Interdepartmental Center, University of Modena and Reggio Emilia, 42124 Reggio Emilia, Italy; [email protected] (F.L.); [email protected] (R.G.) 2 Department of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, 42122 Reggio Emilia, Italy * Correspondence: [email protected] Abstract: The COVID-19 health emergency has imposed the need to limit and/or stop non-essential economic and commercial activities and movement of people. The objective of this work is to report an assessment of the change in vehicle flows and in air quality of a specific study area in the north of Italy, comparing the periods February–May 2020 and February–May 2019. Circulating vehicles have been measured at nine characteristic points of the local road network of the city of Reggio Emilia (Italy), while atmospheric pollutant concentrations have been analysed using data extracted from the regional air quality monitoring network. The results highlight a rapid decline in the number of vehicles circulating in 2020 (with values of up to −82%). This has contributed to a reduction in air concentrations of pollutants, in particular for NO2 and CO (over 30% and over 22%, respectively). On the other hand, O3 has increased (by about +13%), but this is expected. Finally, the particulate matter grew (about 30%), with a behaviour similar to the whole regional territory. The empirical findings of this study provide some indications and useful information to assist in understanding the effects of traffic blocking in urban areas on air quality. Citation: Marinello, S.; Lolli, F.; Gamberini, Keywords: COVID-19; vehicular traffic; air quality; lockdown effects; air pollutants trend R. The Impact of the COVID-19 Emergency on Local Vehicular Traffic and Its Consequences for the Environment: The Case of the City of Reggio Emilia (Italy). 1. Introduction Sustainability 2021, 13, 118. This paper deals with the study of some effects that the COVID-19 lockdown has had https://dx.doi.org/10.3390/su13010118 on road vehicular traffic and on the state of air quality. In particular, this paper describes the trends of vehicular traffic entering and leaving the city of Reggio Emilia (northern Italy) Received: 3 December 2020 through the data collected continuously at some strategic locations positioned at represen- Accepted: 22 December 2020 tative points of the region, as well as the atmospheric conditions and the concentrations Published: 24 December 2020 of some atmospheric pollutants measured during the same period. In particular, the data Publisher’s Note: MDPI stays neu- referring to the following periods have been compared: 1 February—29 May 2019 and 1 tral with regard to jurisdictional claims February—29 May 2020. in published maps and institutional The health emergency related to the spread of COrona VIrus Disease-19 (COVID-19) affiliations. was officially identified for the first time in late December 2019 in the city of Wuhan (China), where a group of patients experienced acute respiratory problems, with symptoms such as fever, cough, dyspnoea and myalgia or fatigue [1–3]. In the following months, helped by population movements, the virus spread rapidly within the Chinese territory and, Copyright: © 2020 by the authors. Li- subsequently, in other parts of the world, infecting in a first phase especially Europe and censee MDPI, Basel, Switzerland. This North America [4,5]. It appears that air and high-speed train (HST) travel have had a article is an open access article distributed strong influence on the spread of the virus [6,7]. under the terms and conditions of the Currently, its spread, albeit with very different levels of contagion, involves practically Creative Commons Attribution (CC BY) the whole world. This prompted the World Health Organization (WHO) to declare the license (https://creativecommons.org/ spread of COVID-19 a global pandemic on 11 March 2020 [8]. licenses/by/4.0/). Sustainability 2021, 13, 118. https://dx.doi.org/10.3390/su13010118 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, x FOR PEER REVIEW 2 of 21 Sustainability 2021, 13, 118 Currently, its spread, albeit with very different levels of contagion, involves practi-2 of 22 cally the whole world. This prompted the World Health Organization (WHO) to declare the spread of COVID-19 a global pandemic on 11 March 2020 [8]. The continuous updating of the data by the WHO indicates that as of 18th December 2020The the continuousconfirmed cases updating in the of world the data are byover the 72 WHO million, indicates with over that 1.6 as ofmillion 18th Decemberdeaths [9]. 2020After the the confirmed initial predominance cases in the world of European are over countries 72 million, in with the overnumber 1.6 millionof infections deaths and [9]. Afterdeaths, the it initialis now predominance the Americas that of European have registered countries the inhighest the number number of of infections cases (over and 31 deaths,million itconfirmed is now the cases), Americas followed that haveby Europe registered (over the 22 highestmillion), number South-East of cases Asia (over (almost 31 million11 million), confirmed the eastern cases), Mediterranean followed by Europe (over (over 4.5 million), 22 million), Africa South-East (about 1.6 Asia million) (almost and 11 million),the western the easternPacific (almost Mediterranean 0.9 million). (over Figure 4.5 million), 1 shows Africa the global (about map 1.6 million)provided and by thethe westernWHO. Pacific (almost 0.9 million). Figure1 shows the global map provided by the WHO. FigureFigure 1.1. ConfirmedConfirmed casescases ofof COVID-19COVID-19 at at international international level—situation level—situation as as of of 18 18 December December 2020 2020 [9 ]. [9]. 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[27] indicates in Wuhan an (China) average and reduction Delhi (India) of 50% and in ofBudapest 93% in Santander(Hungary). (Spain) The use are of describedpublic transport by [28]. services In transport, has dropped the food considerably: retail logistics re- sectorductions has of undergone 80‒90% of a users growth of inpublic demand, transport linked in toWuhan the panic (China) of citizenship, and Delhi the(India) need and to purchaseof 93% in goods Santander for reserve (Spain) purposes are described and the by increase [28].