# Air Quality Improvement in Urban Street Canyons:
## 2 Materials and Methods
### Analyzed Scenarios of Changes in Road Traffic Organization and Adopted Assumptions  
Three exemplary scenarios of changes in the traffic organization described in Table 2 were analyzed for each of the individual street canyons. The analysis also included the possible effects resulting from their implementation in terms of changes in emissions and impact on air quality in the canyon. Potentially feasible scenarios of changes regarding traffic management were developed with the support of the Department of Municipal Services and Climate in the Municipality of Krakow City and took into account:  
* narrowing the street cross section by reducing the number of traffic lanes (elimination of one lane in each direction), changing the use of existing lanes or creating a bus lane (SOLI);
* reducing the speed limit from 50 km\(\cdot\)h\({}^{-1}\) to 40 km\(\cdot\)h\({}^{-1}\) (BROD);
* reducing the speed limit from 70 km\(\cdot\)h\({}^{-1}\) to 50 km\(\cdot\)h\({}^{-1}\) (SOLI, KRAS);
* only passenger cars meeting at least the Euro 4 emission standard and light commercial vehicles meeting at least the Euro 4 emission standard (BROD, SOLI, LIMA, KRAS) are admitted to traffic;
* only passenger cars meeting at least the Euro 5 emission standard and light commercial vehicles meeting at least the Euro 5 emission standard (BROD, LIMA, KRAS) are admitted to traffic;
* only passenger cars meeting the Euro 6 emission standard and light commercial vehicles meeting at least the Euro 6 emission standard (LIMA) are admitted to traffic.  
Figure 5: Structure of vehicles registered in Krakow and other counties of Malopolska Province used in the calculation of pollutant emissions for the baseline variant (v0).  
The profiles of traffic volume and average vehicle speeds for the considered scenarios of road traffic reorganization (variants v1-v3) were estimated based on the measurement data developed for variant v0, and the additional parameters consist of percentage changes in traffic volume and speed from the vehicle stock. The parameters for the scenarios analyzed were calculated using the Krakow Traffic Model [56]. The Krakow Traffic Model is a typical four-stage macrosimulation model that simulates the transport reactions of Krakowian citizens related to daily trips. It was developed in 2015 at the Cracow University of Technology with the use of PTV-Visum software [59], based on research on the behavior of transport system users [60] and measurements of the volume of traffic on the road during the peak hours in the morning and afternoon. Since then, data related to the transport system have been periodically updated in this model by the Municipality of Krakow City Changes in the road network, travelers' transport responses, traffic volume during peak hours and public transport schedules are taken into account.  
For some scenarios, additional assumptions were also included. For example, for the variants that allow the movement of only passenger cars and light commercial vehicles meeting the Euro 4, Euro 5 or Euro 6 emission standards, it was assumed that 5% of the number of real vehicles (known from variant v0) which were excluded from road traffic (vehicles excluded due to non-compliance with a permitted emission standard) would be replaced with new vehicles meeting the Euro 6 emission standard. Therefore, these scenarios should represent the initial situation after the possible implementation of the restrictions analyzed to the organization of road traffic. Furthermore, the assumption that the variability of the traffic speed on each day of the week was the same (according to the daily profile of 1-h average speeds modeled for each scenario) was maintained, as presented in the baseline variant v0.