The impact of COVID-19 restrictions on road traffic and noise pollution of the urban street, a case study from Krakow, Poland

The study determined the impact of restrictions introduced by the Ministry of Health in connection with the COVID-19 pandemic on traffic and sound pressure levels in the university building and its immediate vicinity. Mickiewicza Street was selected for the study. It is one of the city's busiest streets, located relatively close to the old historic center, and is the main artery connecting the north and south of the city. There are residential buildings on this street, but primarily offices and institutions, as well as schools and universities. Noise near the street and in buildings located relatively close to the road can be a serious problem in places where peace is required (e.g., libraries, reading rooms, university halls). Therefore, the acoustic comfort needed in these places may be disturbed, and the perception of knowledge acquisition may be limited. The aim of the work was achieved through measurements and analysis of street traffic intensity and sound pressure levels, taking into account pandemic restrictions. Then, statistical analyses were performed, which showed significant variability in traffic intensity and sound pressure values in individual periods of the pandemic. The pandemic's beginning was mainly characterized by a significant decrease in the above data, deviating from the norm. In the pre-pandemic period, an average of 47,733 vehicles passed through the street daily, and the median sound pressure was L_eq.OUT = 62.0 dBA outside the building and L_eq.INS = 44.0 dBA inside. During the greatest restrictions, a period called "lockdown," the number of cars driving decreased a little to an average of 44,153 per day, but there were days with 10,000-20,000 cars passing. In turn, noise decreased to 59.9 dBA for L_eq.OUT and 43.2 dBA for L_eq.INS. Between the first and second waves of infections, traffic was comparable to the post-pandemic period (an average of 69,027 cars per day), and noise also increased to L_eq.OUT = 64-65 dBA and close to L_eq.INS = 47.5 dBA. Studies have shown that noise on Mickiewicza Street is mainly caused by traffic (correlation coefficient: r = 0.92 for L_eq.OUT and r = 0.86 for L_eq.INS). The sound pressure level is high outside (L_eq.OUT = 63.9 dBA) but relatively low inside the building (L_eq.INS = 47.0 dBA) and should not negatively affect university staff and students (L_eq.WH < L_WH.acc). Based on the analyses, three stages show society's approach to the COVID-19 pandemic: (1) fear of the COVID-19 pandemic; (2) relaxation after restrictions; (3) getting used to the COVID-19 pandemic. These periods did not correlate with the development of the pandemic or the number of people infected and dead.