Due to the increase in the degree of motorization and the number of trips per person, there is a need for better transport systems in their entirety. There is no such thing as a bad solution in traffic systems, however, it is necessary to choose the solution where traffic safety is the highest with the greatest traffic flow. It is too late to react when the solution is implemented and implemented as such in the traffic system. Traffic solutions should be checked before their implementation to see if they work and give them an evaluation of the success of functioning in the traffic system. Today, a large number of microsimulation and macrosimulation computer programs have been developed that try to show us the effectiveness of traffic solutions as best as possible. One of these is the microsimulation program Vissim. The program works on the principle of a stochastic simulation model, which means that for the same input data, the results the program gives are always different. Opatija is a tourist destination where tourism extends throughout the whole year, although most tourists visit it during the summer months. For traffic in Opatija, this means that a large number of motor vehicles are expected to pass through and/or stay in the city in the summer months. Due to the lack of parking spaces, the safety of non-motorized road users and traffic calming in the city center, the idea is to organize traffic only in the summer months in such a way that the road, Ulica Maršala Tita, turns into a one-way road. The reorganization of traffic in Ulica Maršala Tita creates a problem on Nova cesta. The aim of the work is to show how the Nova cesta - in this case the 2nd corridor, functions with additional traffic load taken over from the first long-shore corridor – Ulica Maršala Tita. The results show that with several interventions in the traffic system (adding turning lanes, traffic lights at intersections, etc.), significantly better results can be obtained on Nova cesta, looking at the level of service at intersections, the length of trips, and the like. The use of microsimulation programs proved to be a good solution for evaluating the functioning of the traffic system before making changes in it. The conclusion of the work is that the reorganization of traffic in the summer months would result in safer and calmer traffic in the city center, more parking spaces, but greater congestion and slower traffic flow than before could be expected on Nova cesta. The construction of the 3rd corridor, the Liburnian bypass, which would relieve the Opatija area of transit traffic, would solve all the problems in the city's transport system and relieve it to a large extent.