What is the name of Japan’s longest railway tunnel, linking Honshu and Hokkaido?

The Seikan Tunnel is Japan’s longest railway tunnel, linking Honshu and Hokkaido beneath the Tsugaru Strait. It extends for 53.85 kilometres between Aomori Prefecture and Hokkaido.

Construction began in 1964 after repeated ferry disasters highlighted the danger of the sea crossing. Engineers had to deal with difficult underwater geology, high water pressure, and long stretches of unstable rock.

The tunnel opened in 1988. It originally carried conventional railway services, and it was later adapted for Hokkaido Shinkansen high-speed trains. The line uses dual-gauge track in sections so different train types can operate.

The Seikan Tunnel is sometimes confused with the Channel Tunnel. The Channel Tunnel is longer overall, while the Seikan Tunnel has a substantial section beneath the seabed and remains a major Japanese engineering landmark.