The construction of the D 403 road is one of the most important infrastructure projects in Croatia, and thus the largest project in the City of Rijeka. With the opening of the D 403 road, the direct connection between Port of Rijeka and the road network of the Republic of Croatia and the European Union will be achieved, as well as the connection of the city bypasses and the center of the City of Rijeka. In this final thesis, the existing road network of the City of Rijeka was analysed, as well as the changes in traffic flows that will occur after the construction of D 403 road in the southern part of the route at the intersections of Mlaka and Novi list. In order to achieve that, it was necessary to count the traffic at the existing intersections of Mlaka and Novi list, and to find official data on the amount of traffic that takes place on the street along the mentioned intersections. It was necessery to analise changes in traffic flows for the intersections of Mlaka and Novi list after the construction and commissioning of D 403 road in two phases. The first phase is the construction of the D 403 road to the junction with Ulica Milutina Barača, and the second phase is the construction of the D 403 road through the port area to Ulica Riva. The analyses were created with an assumed traffic distribution for a minimum traffic increase of 20% for Phase 1 and Phase 2, and a maximum traffic increase of 25% for Phase 1 The analyses of the existing road network of the City of Rijeka and the intersection in the southern part of the route of the road D 403 were used to determine the redistribution of traffic after the construction and commissioning of the road D 403.