The current state of the Karlovac-Oštarije railway section does not meet the technical and technological requirements that must be met by the main corridor railway lines for international traffic, does not meet the technical specifications for the interoperability of the railway system and its permeability does not meet the planned traffic on the section in question. The aim of the project is to prepare study and project documentation for the modernisation and construction of the Zagreb-Rijeka traffic route on connecting the wider area of Karlovac and Oštarije, in addition to meeting the technical and technological conditions that must be met by the main corridor railways for international traffic, which will be achieved through phase 1 and phase 2.