 The national road network has a total length of 40 @,@ 231 kilometres ( 24 @,@ 998 mi ) , of which 39 @,@ 587 kilometres ( 24 @,@ 598 mi ) are paved , but nearly half fall into the lowest international rating for paved roads . Railroads are a major mode of freight transportation , although highways carry a progressively larger share of freight . Bulgaria has 6 @,@ 238 kilometres ( 3 @,@ 876 mi ) of railway track and currently a total of 81 km of high @-@ speed lines are in operation . Rail links are available with Romania , Turkey , Greece , and Serbia , and express trains serve direct routes to Kiev , 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 . Varna is also scheduled to be the first station on EU territory to receive natural gas through the South Stream pipeline . 
