# Air Quality Improvement in Urban Street Canyons:
## 1 Introduction
This assessment was carried out based on the estimated changes in the emissions of the analyzed substances for individual scenarios, and the results of the modeling of their concentrations in the air was carried out with the use of the Operational Street Pollution Model (OSPM), dedicated to street canyons [35; 36; 37]. The OSPM model had already been used for similar purposes, including by [PERSON] and [PERSON] (Ghent, Belgium) [38], [PERSON] and [PERSON] (Montreal, Canada) [39], [PERSON] et al. (Belgrade, Serbia) [40], [PERSON] et al. (Riga, Latvia) [41] and [PERSON] et al. (Krakow, Poland) [26]. It is also known to have been used to model air pollutant concentrations for a larger number of street canyons or the entire network of high streets in large cities. Examples of such an application of the OSPM model include studies that evaluate the effect of the European strategy to control emissions from road transport before 2030 on air quality in 20 cities located in northern and southern Europe [42], the analysis of the effect of introducing a vehicle speed limit 30 km\(\cdot\)h\({}^{-1}\) on the level of NO\({}_{2}\) concentrations on one of the weekends in Munich (Germany) [43] or the influence of various traffic management strategies in Dublin (Ireland) on air quality and public health [44]. Earlier research conducted in Krakow by [PERSON] et al. [26] involved assessing the influence of three traffic reorganization scenarios on air quality, considered for one of the sections of 29-Listopada Av., which is an exit route from the city center to the north, with a traffic volume of 19.5 million vehicles per year. The scenarios analyzed included: narrowing the cross section of the street by eliminating one lane in each direction (from three to two lanes), limiting the speed limit from 70 km\(\cdot\)h\({}^{-1}\) to 50 km\(\cdot\)h\({}^{-1}\) and admitting only passenger cars and light commercial vehicles meeting Euro 4 emission standards or higher. This paper presents the results of subsequent studies assessing the impact of traffic management scenarios on air quality in street canyons in Krakow, such as reducing the number of lanes, reducing the speed limit or applying restrictions to vehicles, for four streets that are different in terms of their volume, structure, and average speed of vehicle traffic, as well as the geometry of their canyons and the location of their axes in relation to the prevailing wind directions. These studies included e.g., the Krasirnskiego Av. (KRAS) street canyon, with a traffic volume of over 24 million vehicles annually, where the communication-type air quality monitoring station was located, which had already been used several times to verify the OSPM model [45; 46]. The research conducted is part of a larger action aimed at selecting optimal methods to reduce emissions from road transport and further improve air quality in Krakow. Most of the already implemented and planned activities are based on reducing vehicle traffic in the city center by expanding the paid parking zone, optimizing various traffic engineering solutions, strengthening the role of public transport and promoting ecological forms of travel supported by the construction of an integrated metropolitan transport system, a network of ring roads and bicycle paths, P&R (park and ride) car parks, electric vehicle charging stations and electric bike or scooter rental system [47; 48; 49; 50; 51; 52; 53]. Subsequent measures will aim to introduce clean transport or low-emission zones in Krakow, of which, various scenarios are already provided in the new air quality plans for the Malopolska Province [54].