The current state of the Karlovy Vary section does not fulfil the engineering conditions which must be met by the major corridor railway lines for international transport, do not meet the technical specifications for the interoperability of the rail system and do not meet the technical specifications for the interoperability of the rail system. the aim of the project is to draw up the study and project documentation for the modernisation and construction of the Zagreb — Rijeka section to connect the broader Karlovac and Osoles’ section, while meeting the technical technology conditions which must comply with the major corridor railway lines for international traffic.