Length of tunnels in Japan 2020, by interior
As of March 31, 2020, tunnels with a standard lining added up to approximately 3.24 thousand kilometers in length. The term tunnel refers only to structures that have been built for passing through natural obstacles like mountainsides, plateaus, the underground, river bottoms, et cetera. Consequently, the statistic does not include underground crosswalks, box culverts, rock or snow sheds, and similar.