Inbi-sen 因美線

This non-electrified, single-track line used to be the northern half of a link from the Inland Sea (Okayama City) to the Japan Sea (Tottori City) via the old castle town of Tsuyama, situated in the centre of Western Japan's Highlands. The Okayama - Tsuyama section is operated as the Tsuyama-sen, and the continuation from Tsuyama to Tottori as the Inbi-sen.

The climb up into the highlands from Okayama into the Tsuyama basin (i.e. the Tsuyama-sen) involves steep gradients and tight curvature, but this is nothing compared to the extremely difficult conditions which the Inbi-sen needs to tackle on its climb up to the summit tunnel in the mountains separating the Okayama and Tottori Prefectures. After the summit tunnel the Inbi-sen descends steeply through mountain villages northwards to Chizu, and from there on along the river to Kôge and Tottori.

Since a through express service ended in 1997, the Inbi-sen has no more direct trains between Tottori and Tsuyama. As from 1994 the lower, northern half of the Inbi-sen from Tottori to Chizu (31, 9 km), has been operated by the newly built private Chizu Kyûkô Railway with its HOT rolling stock (H=Hyôgo Prefecture, O=Okayama Prefecture, T=Tottori Prefecture). HOT express trains connect Tottori (a few coming from/going to Kurayoshi, west of Tottori) with Himeji, Ôsaka and Kyôto every 2 hours (journey time being 3 hours). Local trains of the Chizu Kyûkô work up the Inbi-sen from Tottori as far as Kamigôri on the San'yô Honsen.

The express trains from Okayama to Tottori via Kamigôri and the Chizu Kyûkô line (journey time roughly 2 hours) also operate every other hour, so that a fairly good service is provided on the lower half of the Inbi-sen between Chizu and Tottori (two different express services and the Chizu Kyûkô local service). In addition, trains of the private Wakasa Tetsudô, coming from Wakasa, also serve the Inbi-sen between Kôge and Tottori (10, 3 km).

The two-car diesel express trains on the Okayama – Tottori service are (with exception of an early morning service from Chizu to Yonago) the only JR trains to operate on the lower, northern half of the Inbi-sen.

The southern half of the Inbi-sen, between Chizu and Tsuyama (actually Higashi (East) Tsuyama, 38, 9 km, plus a short run of 2, 6 km over the Kishin-sen to reach Tsuyama station) has very little traffic and is worked by a single JR railcar of class 120. 7 trains per day work the line, with another 3 working part of the way. There is also one special seasonal train.

Freight services ended in 1987. On July 5, 2018 the line was very badly damaged by torrential rain and landslides; full services were resumed on August 31.

The Inbi-sen was opened from Tottori to Chizu between 1919 and 1923, and from Higashi Tsuyama to Chizu between 1928 and 1932. The lines takes its name from the old province of Inaba 因幡, the Eastern part of present-day Tottori Prefecture, and the old province of Mimasaka 美作, the north-eastern part of present-day Okayama Prefecture. Together the characters 因　and美　are read "Inbi".

Cherry blossom season with diesel car KIHA 120-339 at Miura, on the climb up from Tsuyama northwards. (2015)

From a train heading for Chizu from Tsuyama. KIHA 120 339 at Takano station, slightly north of Tsuyama. (2015)

Approaching Mimasaka Takio. (2015)

Between Mimasaka Takio and Miura, at the start of the climb northwards into the mountains. (2015)

Miura halt, about 14 km north of Tsuyama. (2015)

Following the river between Miura and Mimasaka Kamo. (2015)

Near Chiwa, about 21 km north of Tsuyama. (2015)

At Chiwa halt. (2015)

Below Mimsaka Kawai on the south side of the climb up to the summit tunnel. (2015)

Mimasaka Kawai halt with the remains of an old crossing. (2015)

On a train heading for Tsuyama - Coming down from the summit tunnel towards Mimasaka Kawai. The house in the foreground used to have a thatched roof, as can be seen in an earlier picture of the same spot. (2015)

On a train heading for Tsuyama - Coming down from the summit tunnel towards Mimasaka Kawai. The house in the foreground now has a new roof, as can be seen in a later picture of the same spot. (2009)

Tackling the very difficult route on the south side of the summit tunnel (above Mimasaka Kawai). Speed is often reduced to 25 or even 15 km/h, and in rainy weather 15 km/h is additionally enforced in many places. (2015)

After passing through the summit tunnel on its journey from Tsuyama to Chizu the train enters Tottori Prefecture. (2015)

At Nagi, on the way down to Chizu. (2015)

Nagi station in the rain, with KIHA 120-355 in the mirror.

Chizu Junction, seen from an Inbi-sen train coming from Tsuyama. In the distance a Chizu Kyûkô local train for Kamigôri can be seen waiting in the station. (2015)

Class 120 no. 339 leaving Chizu Junction on its way back over the mountains to Tsuyama. (2015)

Seen from a Chizu Kyûkô train leaving Chizu, JR diesel car KIHA 120-339 is heading southwards towards the summit tunnel and Tsuyama. (2015)

Following the river near Inaba Yashiro, north of Chizu. (2015)

Inaba Yashiro halt, north of Chizu, with Chizu Kyûkô cars 3509 and 3501 in the mirror. (2009)

Chizu Kyûkô local train set from Tottori via Chizu to Kamigôri. Cars 3509 and 3501 at Mochigase. (2009)

Mochigase station, between Kôge and Chizu. The two Chizu Kyûkô local train diesel cars (nos. 3504+3503) are seen in the mirror, while an express from Okayama to Tottori (a pair of JR cars of class KIHA 187-500) crosses. (2015)

From the train near Kunifusa, south of Kôge. (2015)

A Chizu Kyûkô express train from Kyôto via Ôsaka and Kamigôri, headed by HOT 7013, stops at Kôge. (2009)

From a Chizu Kyûkô local train (Tottori - Chizu) heading south towards the mountain range dividing the Japan Sea side and the Inland Sea side. Near Kôge. (2009)

Wakasa Tetsudô car "Sakura 3" passes at Tsunoi between Kôge and Tottori. (2015)