The research problem in this dissertation is an analysis of the impact of internalization of external costs, i.e., the application of the current United Nations and European Union traffic policy, to changes of dynamics, intensity, structure, and directions of freight flows in Northern Adriatic region. Analysis of potential changes in the consolidation of freight flows is carried out under current conditions of the traffic surroundings taking into account the Northern Adriatic and competitive traffic directions as well as the common interest market. The research was carried out on the example of intermodal, maritime-rail transport on the traffic routes from the Far East towards the selected Central European destinations, as the markets of interest for Northern Adriatic ports. The study used statistical methods, the method of Data Envelopment Analysis (DEA) and numerous software tools (EcoTransIT, Frontier Analyst, etc). In this model set up, the North Adriatic transport route towards Central European destinations is more competitive than the alternative, Mediterranean and Northern European directions. Decisiveness in the implementation of the policy of sustainable traffic development and preparedness of North Adriatic ports to provide at least the same quality of service as compared to competitive harbors are preconditions for the potential redirection of freight flows towards the Northern Adriatic region. The results of research confirm the socio-ecological criteria as relevant factors for the formation of freight flows, the sustainability, and competitiveness of the traffic routes, and DEA as a credible method of testing the efficiency of sustainable transport. In the applicative sense, the contribution of this research reflects a present model of predicting the intensity, structure, dynamics, and directions of freight flows, which, by taking into account external costs as a factor of sustainability, will potentially be consolidated otherwise. With the overall growth rate of maritime traffic by 3.2% to 2022, the results predict the dynamics of freight flows growth in Northern Adriatic ports up to 25%, whereas in the Northern European ports the intensity of the freight flows would decrease by 4-5% compared to the referent year 2017.