The national road network has a total length of , of which  are paved. Railroads are a major mode of freight transportation, although highways carry a progressively larger share of freight. Bulgaria has  of railway track,  with rail links available to Romania, Turkey, Greece, and Serbia, and express trains serving direct routes to Kyiv, Minsk, Moscow and Saint Petersburg. Sofia and Plovdiv are the country's air travel hubs, while Varna and Burgas are the principal maritime trade ports.