Hôhi Honsen 豊肥本線

This line is also known as the Aso Kôgen-sen (The line across the Aso plateau), and it runs straight through the centre of Kyûshû, from Kumamoto in the west to Ôita in the east. On its way, the Hôhi-sen needs to climb up to and traverse the huge caldera of Mount Aso, an active volcano that erupts at regular intervals, the last eruptions having been in 2015 and 2016. The Aso caldera measures about 25 km from north to south, and 18 km from east to west. Inside the caldera, the line serves several agricultural settlements, passing along the foot of five major and several smaller volcanoes with their bizarre geological formations.

Starting in the west at Kumamoto, the Hôhi-sen operates as a suburban electrified line (electrified in 1999, 20 kV/60 Hz) to Higo Ôzu. From there starts the (non-electrified) climb up into the Aso caldera, first reaching the switchback station of Tateno; here the former JNR line to Takamori (now the private Minami Aso Tetsudô) branches off and runs along the southern foothills of the volcano. Trains on the main line reverse and tackle the very steep incline to a point high above Tateno. There trains reverse again and follow the outside of the caldera, before entering it through the opening created by the Shirakawa river. In only 6 km the Hôhi-sen climbs from an altitude of 277, 4 m at Tateno to 467,4 m at Akamizu.

After traversing the Aso caldera, the small town of Miyaji is reached. From here trains soon pass through the eastern caldera wall and begin their steep descent to Ôita via the town of Bungo Taketa, famous for its song "Moon over the Ruined Castle". The complete length of the Hôhi-sen is 148, 0 km.

The Hôhi-sen has been affected by torrential rain and storms ever since it was built (a large part in 1914) and completed in 1928 (the last section completed being the incline from Tamarai to Miyaji on the eastern side). The line was destroyed several times in recent years, and major interruptions of services were from July 1990 (interrupted for 15 months), September 1993 (8 months), September 2004 (3 months), July 2012 (2 months, but as the tunnels on the section between Bungo Taketa and Miyaji were internally destroyed, trains could not run here for 13 months). Again, in September 2017 part of the line on the eastern side could not be operated for a month.

The worst disaster to hit the line were the violent Kumamoto earthquakes of April 14, 2016 (foreshock) and April 16, 2016 (main shock, magnitude 7, 3). Following these quakes, which also derailed a train on the western side, the Hôhi-sen had to be closed down; the main section between Higo Ôzu and Bungo Taketa was out of use for a long period. Bungo Taketa to Bungo Ogi could be reopened on April 28, 2016, and Bungo Ogi through Miyaji to Aso on July 9, 2016. However, the rest of the line between Higo Ôzu and Aso, remains out of use for the time being. It is expected that Higo Ôzu to Tateno will reopen eventually, but the switchback line from there and the climb through Akamizu to Aso is destroyed through the spectacular collapse of the mountainside. At present, it is impossible to tell when – and even if – this part of the Hôhi-sen can be reopened, as the damage to railway line and road, particularly above and to the east of Tateno, is immense.

# Services between Bungo Ogi and Aso were reinstated in July 2016

Before the earthquake, services consisted of frequent commuter trains between Kumamoto and Higo Ôzu, and of local trains between Kumamoto and Miyaji at irregular intervals throughout the day. Between Bungo Taketa and Ôita the timetable shows a fairly regular service, but the section between Miyaji and Bungo Taketa was served only by 5 local trains a day. In addition, we had 4 express trains over the whole line and a few seasonal express trains from Kumamoto to Miyaji.

Today, the Hôhi-sen (apart from the commuter trains Kumamoto-Higo Ôzu) has fairly regular local services between Ôita and Bungo Taketa, with 3 to 4 local trains a day between Bungo Taketa and Aso, and an evening train between Bungo Taketa and Miyaji. In addition, 2 express services and 2 seasonal services are provided on the Aso to Ôita section. The line between Higo Ôzu and Aso remains closed.

The name of the line, Hôhi Honsen (Hôhi Mainline), derives from characters standing for the names of old provinces, namely Bungo (豊後), the old name of a large part of present-day Ôita prefecture, and Higo (肥後), the old name for what is now Kumamoto prefecture. The two characters 豊肥　together are pronounced "Hôhi". The border between Kumamoto and Ôita prefectures (i.e. between Bungo and Higo) runs through the east side of the Aso caldera, west of Bungo Ogi.

Diesel motor coach 220-204 at Bungo Taketa. (2016)

Higo Ôzu, the end of the electrified suburban section. Electric two-car train 815-11 and the diesel train set 200-102 that will continue to Miyaji. (2013)

A train (composed of diesel cars class 58) descending in the switchback towards Tateno. Through the collapse of the mountainside to the left the line has been destroyed. (1972)

Locomotive 69699 bringing a freight train up to Tateno. (1972)

In the switchback above Tateno. Loco 69699 pushes its train upwards and will then reverse again and continue forward into the Aso caldera. (1972)

Train KIHA 200-2 + KIHA 1002 at Takenaka on its way from Ôita to Bungo Taketa. (2016)

Asaji station near Bungo Taketa. (2016)

Miyaji station with diesel train KIHA 200 101 + KIHA 200 101 and diesel car KIHA 125-111. In the background the inner wall of the Aso caldera. All traffic is suspended here after the Kumamoto earthquake of April 2016.

The Aso volcano at Miyaji. Train KIHA 200 101 has stood here for several weeks following the Kumamoto earthquake. (2016)

Aso station with the inner wall of the caldera in the background. Train set KIHA 147 61 + KIHA 147 1058 + KIHA 31 19. (1997)

Suizenji, in the eastern part of the city of Kumamoto. (2018)

Early morning on the electrified section between Kumamoto and Higo Ôzu. Trains 815-9 and 815-5. (2018)

Ichinokawa, the second station after reaching the Aso caldera from Tateno. The inner wall of the caldera can be seen in the background. Since the devastating earthquakes in April 2016 train services are suspended here. (2018)

Aso station with diesel cars KIHA 125-10 and -16. Since reopening of the line from the east after the earthquakes of 2016 trains end here. (2018)

Climbing up the inner wall of the Aso caldera to reach the summit tunnel, after which the train will tackle the steep descent towards Bungo Taketa. (2018)

On the descent towards Bungo Taketa, below Takimizu. (2018)

Ogata, between Bungo Taketa and Ôita. The train crossing on its way up to Miyaji is the two-car set KIHA 200-4 + KIHA 200-1004. (2018)

At Miemachi, one of the larger stations between Bungo Taketa and Ôita. Diesel cars KIHA 125-10 and 125-16. (2018)

Takenaka, from diesel car KIHA 125-111 descending towards Ôita. (2018)

The famous aqueduct (built in 1917) over the Sasamuta river just below Bungo Taketa. (2018)

The tourist panoramic train (KIHA 183-1001) descending from the Aso caldera back to Ôita. At Namino, the first stop after passing through the east-side caldera summit tunnel. (2018)

Diesel car KIHA 220-204 returning from Aso station towards Miyaji. (2018)

As the railway line west of Aso station has been destroyed in the earthquakes of April 2016 traffic needs to climb up over the caldera wall to reach Tateno and Kumamoto. View taken from the railway replacement bus looking down over the Aso volcanoes and the village of Akamizu. (2018)

Between Higo Ôzu and Tateno, looking towards the Aso volcanoes. As rail services are suspended the line is totally overgrown. (2018)