The basic purpose and objective of the research in this doctoral thesis entitled "Model of marine traffic flow organization in the approaching waterways" is to describe and quantify the safety of navigation in the approaching waterways and to determine the optimal organization of marine traffic flow. The objective is achieved by creating a conceptual model of marine traffic flow organization. In this model, the safety of navigation is represented by the function of safety as the combination of general safety function and the function of increased risk. The first function describes the general state of marine traffic in the waterway, while the second one describes the safety of navigation in increased risk. Function of safety is defined by elements of the safety of navigation and safety coefficients that depend on the characteristics of the marine traffic in the navigable area. By changing the value of safety coefficients the universality of the model is achieved, resulting in the possibility of using the model in different navigable areas. While using the same values of the coefficients, the safety function allows comparison of various levels ofthe safety of navigation in different marine traffic situations. Testing of the model was performed by means of a dynamic simulation model using real data on marine traffic. Simulation results support the possibility of using the model for determining the optimal marine traffic flow organization in the approaching waterways and consequently for increasing safety of navigation and efficiency of marine traffic flow. The significance of the proposed model Lies in the possibility of its practical application for the establishment of appropriate measures and activities aimed at improving safety of navigation, primarily through optimization of the vessel traffic services. safety of navigation, marine traffic flow, model of marine traffic flow organization, approach ing waterways, function of safety