The Budapest–Belgrade–Skopje–Athens railroad is a planned project of a high-speed railroad track which will start in Budapest, via Belgrade and Skopje to Athens. The Budapest–Belgrade railway will be finished in two years. Planned speed is 160 km/h between Budapest and Belgrade, current line between Thessaloniki and Athens is 200 km/h with upgrades to 250 km/h ongoing.
References
Budapest–Belgrade–Skopje–Athens railway Wikipedia(Text) CC BY-SA