## 6 Conclusions  
This study illustrates once again the complexity of urban planning and the importance of a detailed analysis not only for urban planning and transportation concepts but also of the complex socioeconomic aspects as a result of the transformation of the urban mobility network. The determination of mobility patterns and scenarios is not possible without the usage of a complex information system that can integrate all spatial aspects in order to identify an optimal urban solution already in the planning phase. The research objective of this article is focused on the evaluation of an investment in the optimization of traffic by the construction of an underpass and to analyze the impact of this investment on traffic-related air pollution. The first conclusion is that the construction of the underpass reduces the number of accidents in the intersection but has no effect on traffic improvement, because the analysis shows that all traffic problems at the intersection were shifted to the adjacent intersections after the construction works. The second conclusion is that the above investment has no significant impact on air pollution, except during the COVID-19 pandemic restrictions. The main conclusion from this study is that geographic information systems, due to their many advantages, are optimal tools not only for analyzing traffic and its impact on the urban environment, but also for modeling and solving traffic problems, especially because of their ability to combine traditional geospatial data with remote sensing data and data collected through crowdsourcing. The emphasis on the interaction between the transportation system and its environment makes the methodology proposed in this article, based on the GIS technology, applicable not only for route planning and risk analysis, but also for planning new access roads and decision making for urban traffic optimization and congestion relief. Another important conclusion that can be drawn from the analysis is the usefulness and applicability of transportation data collected through crowdsourcing to analyze the transportation system in all phases of an urban redevelopment project: planning, design, implementation, and monitoring. The method of data collection through crowdsourcing of road users can replace the method of counting vehicles in traffic as it is less costly to implement. By using geographic information systems in combination with open-source, real-time traffic monitoring systems, we can optimize urban transportation planning projects and, in this way, contribute to sustainable urban development. Rehabilitation and redesign of problematic intersections as well as access roads can have an impact on reducing traffic congestion, which has a multiplier effect on pollution reduction and sustainable urban development. Smooth, congestion-free traffic drastically reduces the time that commuters spend in traffic and therefore has many positive impactson people and the environment. Road transport is a major source of air pollution, directly through the emission of exhaust gases, but also indirectly through the consumption of fossil fuels. The main advantages of the methodology proposed in this study, based on the analysis of geospatial data, crowdsourcing data and remote sensing, are  
* the possibility of applying it anywhere in any urban agglomeration or region,
* the versatility of its application, including the preliminary planning of urban development projects to reduce traffic congestion,
* that it can be a reliable source of information for the environmental and ecological impact analysis of infrastructure investments, and
* its applicability in carrying out socioeconomic analyses. The study has some potential limitations, such as the lack of air-quality data from ground sensors with more reliable information than remote sensing data, which can be modified by atmospheric conditions.