Ômura-sen Nagasaki-sen 大村線 長崎線
Ômura-sen -- running along Ômura Bay, between Sonogi and Chiwata. The train is class 66/67 no. 11. (2018)
Nagasaki-sen -- climbing up from Ôgusa and Ômura Bay towards the summit tunnel leading across to Nagasaki. (2018)
The Ômura-sen runs along the eastern coast of Ômura Bay, which is almost completely enclosed, in the west by Nishi Sonogi Peninsula and in the south by Nagasaki Peninsula. Only a small opening in the north between a group of islands in the Sasebo region gives passage to ships into Ômura Bay. At the southern end of the Ômura-sen at Isahaya most trains turn sharply to the west into Nagasaki Peninsula to reach Nagasaki either directly via the Nagasaki Honsen and the new tunnels opened in 1972, or on the old line across the mountains via Nagayo, opened in 1897/8. This old line is often referred to as the Nagasaki-sen (in contrast to the Nagasaki Honsen).
The Ômura-sen from Haiki in the north to Isahaya in the south (built 1898) once formed a section of the main line from the city of Fukuoka (Hakata station) to Nagasaki, until trains started running along Ariake Bay to Nagasaki in 1934. The line is 47, 6 km long; since 1992 the section from Haiki to the theme park Huis Ten Bosch (pronounced haus-ten-boss and recreating the Netherlands) is electrified (20 kV/60 Hz) for through express trains from Hakata via the Sasebo-sen.
Most Ômura-sen trains today continue from Haiki northwards to the town of Sasebo.
Whereas fast Ômura-sen services (called "Seaside Liner") between Nagasaki and Isahaya go straight through the long tunnels connecting the two towns, stopping trains leave (or join) the main line at Kikitsu (6, 5 km from Isahaya) an serve the local villages along the Nagasaki-sen (23, 5 km long). They branch off from (or regain) the Nagasaki Honsen at Urakami, 1, 6 km north of Nagasaki.
The Ômura-sen has a service roughly every half hour, on an alternating basis with one Seaside Liner and one stopping train. Between Isahaya and Nagasaki via Nagayo there is a through train roughly every hour, with additional services between Nagayo and Nagasaki.