Kanmon Tunnel　　関門トンネル

A train for the shuttle service through Kanmon Tunnel in Moji. On the right is the descent into the tunnel. Dual-current Electric Multiple Unit class 415, no.126. (2016)

In a shuttle service train through Kanmon Tunnel. View from just south of Shimonoseki across Kanmon Strait over to Kyûshû. (2016)

The Kanmon Tunnel connects Japan's main island Honshû with the island of Kyûshû in the southwest. Apart from numerous through trains carrying containers it is served by a regular shuttle passenger service operated by JR Kyûshû between Shimonoseki (on Honshû) and Kokura (on Kyûshû), a distance of around 12 km covered in just under 15 minutes. The actual tunnel section is between a point slightly south of Shimonoseki and the station of Moji on Kyûshû. A few trains to and from Shimonoseki continue down the Nippô Honsen in the direction of Nakatsu.

Formerly the Kanmon Tunnel saw through intercity, sleeping car and regional trains covering vast distances on Honshû and Kyûshû, but today all major passenger services are worked over the Shinkansen line and through the New Kanmon Tunnel, completed in 1975.

The Kanmon Tunnel consists of two separate tubes, one for the north-south direction, opened in 1942, and one for the south-north direction, opened in 1944. Both tubes are around 3, 6 km in length. A bridge over the Kanmon Strait was considered impractical in view of the heavy shipping traffic, and - at the time - also for security reasons. On the Shimonoseki side the gradient down under the sea is 22 ‰, on the Moji side 25 ‰ .

Originally, the line was electrically operated using DC 1500 V. With the electrification of the main lines on Kyûshû, using AC 20 kV/60 Hz, a switchover point DC / AC was installed for the trains emerging from Kanmon Tunnel at the entrance to Moji station. Both the electric multiple units as well as the locomotives used on passenger, sleeping car and freight trains have all been dual current vehicles (DC / AC) from 1960 onwards.     

The name "Kanmon" is a combination of the two place names Shimonoseki (written 下関 ) and Moji (written 門司 ). The two characters 関門 read together are pronounced "Kanmon".

A long container train headed by dual-current two-unit electric locomotive EH 500-45 has come through the Kanmon Tunnel from Honshû. Seen between Yahata and Edamitsu in the industrial surroundings of northern Kyûshû. (2015)

For the passage under the sea many trains used to switch to haulage by special dual-current locomotives class EF 30 with unpainted corrugated stainless steel bodies. (1972)