# Air Quality Improvement in Urban Street Canyons:
## 3 Results  
### Volume and Speed of Vehicle Traffic Determined for the Analyzed Variants  
Figure 7 shows the profiles of the average traffic volume with a 95% confidence interval for the individual scenarios of traffic reorganization in terms of hours and days of the week. Table S1 (Supplementary Materials) presents a summary of the total annual and average annual values of the vehicle traffic volume forecasts for the scenarios and street canyons  
Figure 6: Scheme presenting the research methodology along with the places where meteorological and background pollution data were used. considered. The percentage rate of traffic volume reduction obtained for variants v1-v3 in relation to the baseline variant v0 is visualized in Figure 8.  
Among the analyzed scenarios of changes in the organization of road traffic, the highest rates of vehicle traffic volume reduction in relation to the baseline variant (v0) were obtained for the variants in which the criterion of compliance with the Euro 4, Euro 5 or Euro 6 emission standards were implemented. The introduction of these scenarios resulted in a reduction in traffic volume of approximately 45-79%, depending on the emission standard criterion adopted (Figure 8). This was due to the large share of older cars that did not meet the given criterion in the vehicle structure determined for the baseline variant and the additional assumption that only 5% of the vehicles eliminated in this way from traffic would be replaced by the newest vehicles meeting the Euro 6 emission standard. In the case of the scenario in which passenger cars and delivery vans meeting the Euro 6 emission standard (the LIMA street canyon, variant v3) were admitted to traffic, the average reduction in traffic volume was predicted at a level of approximately 78.7% compared to variant v0. However, the variants based on the elimination of only those vehicles that did not meet the Euro 5 and 4 emission standards, respectively,  
Figure 8: Average rate of vehicle traffic reduction in variants v1–v3 compared to variant v0. Figure 7: Daily and weekly profiles of vehicle traffic for individual variants and street canyons with 95% confidence intervals. were characterized by a reduction in traffic volume of approximately 67.5% and 44.8%. Statistical analysis showed that these variants compared to variant v0 are statistically significantly different at the 95% confidence intervals (Figure 7). In the case of the remaining traffic reorganization scenarios analyzed for some street canyons (BROD, SOLI, KRAS), the predicted reduction in traffic volume in relation to variant v0 was achieved at a much lower level (of 3-10%). In these cases, the calculated 95% confidence intervals for the average traffic volume overlapped (Figure 7). This means that these scenarios do not result in statistically significant changes in traffic volume. The variability of 1 h vehicle traffic speeds for all variants of traffic organization analyzed in the considered street canyons (average values for traffic in both directions) is presented in Figure 9. Limitation of the average speed of vehicle traffic relative to the baseline variant (Table 1) was provided only for the variant v1 for the BROD, SOLI and KRAS street canyons (averaged real reductions amounted to 17.9%, 5.5% and 17.9%, respectively) and for variant v2 for the SOLI canyon (reduction of 17.5%) (Table S2). The introduction of emission reduction scenarios also affects vehicle speed profiles. As a rule, a decrease in traffic intensity results in an increase in the speed of moving vehicles (Figures 7-9). Variant v2 for SOLI is an exception (Figure 9b), because this scenario takes into account the planned  
The data presented show that the calculated average annual pollutant emission rates (Table 3) are most frequently directly proportional to the volume of vehicle traffic summarized for individual variants in Tables 1 and 3.