Dosan Line
Nanpū 2000 series DMU at Sanuki-Saida Station
Overview
Status	In operation
Owner	JR Shikoku
Locale	Kagawa,Tokushima,Kōchi Prefectures
Termini	Tadotsu Kubokawa
Stations	61
Service
Type	Heavy rail
History
Opened	23 May 1889; 136 years ago (1889-05-23)
Completed	12 November 1951; 74 years ago (1951-11-12)
Technical
Line length	198.7 km (123.5 mi)
Number of tracks	1
Character	Rural
Track gauge	1,067 mm (3 ft 6 in)
Minimum radius	200 m (660 ft)
Electrification	1,500 V DC overhead catenary (Tadotsu - Kotohira)
Operating speed	120 km/h (75 mph)
Route map

TheDosan Line (土讃線,Dosan-sen) is a railway line inShikoku, Japan, operated by theShikoku Railway Company (JR Shikoku). It connectsTadotsu Station inTadotsu,Kagawa, andKubokawa Station inShimanto,Kōchi. The line links the city ofKōchi with northern Shikoku and the island ofHonshū via theSeto-Ōhashi Line. The first section of the line between Tadotsu andKotohira opened in 1889, Kochi was connected to the northern section of the line in 1935, and the western extension of the line was completed in 1951. The name of the line comes from "Tosa" (土佐) and "Sanuki" (讃岐), the oldprovincial names of present-dayKōchi Prefecture andKagawa Prefecture, respectively.

The first section opened, between Tadotsu and Kotohira, was constructed by the Sanuki Railway Co. in 1889. The company was nationalised in 1906.

The Kotohira - Awa Ikeda section was opened in 1914 and connected to the Tokushima line.

The Susaki - Kochi - Kusaka section opened in 1924, and was extended north in sections 1925-35, where it connected to the northern section at Minawa, the line from Awa Ikeda having been extended there in 1931.

The Susaki - Tosakume section opened 1939, with extensions to Kageno opening 1947 and to Kubakawa in 1951.

CTC signalling was commissioned between Tadotsu - Kochi in 1967, and the 4,180m Oboke tunnel and associated realignment opened the following year.

The 2,583m Osugi tunnel and associated realignment opened in 1973. CTC signalling was extended to Kubokawa in 1986, and the Tadotsu - Kotohira section was electrified the following year prior to the privatization of JNR. However, the maximum speed of electric trains in this section is limited to 85 km/h due to the overhead catenary being a direct-line suspension system (similar to trams) as a result of a lack of funds during construction at the end of the JNR era. On the other hand, the diesel-powered limited expressJR Shikoku 2000 series is able to run at 120 km/h, while regular diesel trains can run at 95 km/h. As such, the diesel trains operating in this section is able to run faster than electric trains. To reduce the burden on the overhead catenary, electric trains operate with only one raised pantograph in addition to the speed limit. The overhead catenary of platform 1 at Kotohira Station is the only section along the entire line to have a Simple Catenary System typically used on electrified JR lines.

After the privatization of JNR, there was a plan to electrify the Dosan Line to Awa-Ikeda along with theYosan Line, but the former did not come to fruition. The reasoning being the low return on investments due to the sharp decline in traffic south of Kotohira, and the many narrow tunnels making the installation of overhead wires difficult. As such, it was decided that a more rational plan was to introduce new high-speed diesel trains for limited express operations as opposed to electrification. In a 2006 submission to the subcommittees of the Ministry of Land, Infrastructure, Transport and Tourism, JR Shikoku cited the electrification of the Kotohira - Kochi section as one of the desired long-term investments.

Freight trains ceased operating between Tadotsu - Kochi in 2005.

• Kotohira station - The Kotohira Express Railway Co. operated a 16 km line to Sakaide on theYosan Line 1930-44, with the line formally closing in 1954.
• Tadotsu station - The Kotohira Sangu Railway Co. operated a 27 km line to Sakaide 1922/28 - 1963, with a 7 km branch to Kotohira operated 1923-63.

Nanpū (南風) limited express trains make 14 round-trips per day betweenOkayama andKōchi,Nakamura, orSukumo.Shimanto (しまんと) limited expresses make five round trips per day betweenTakamatsu and Kōchi, Nakamura, or Sukumo. TheSunport (サンポート) rapid service trains linkKotohira and Takamatsu once an hour.

The line is generally divided into three parts for local services atAwa-Ikeda and Kōchi. For the segment betweenTadotsu and Kotohira, there are through services to/from Okayama and Takamatsu. TheTosa Kuroshio RailwayGomen-Nahari Line has through service to/from Kōchi.

• Local trains generally stop at all stations, but sometimes skip stations marked "▽".
• Sunport (Takamatsu - Tadotsu - Kotohira) rapid trains stop at all stations on the Dosan Line.
• See the articles on theNanpū andShimanto limited express services for details of station stops.
• Trains are able to pass each other at stations marked "◇" and "◆" (switchback); trains cannot pass at stations marked "｜".

• List of railway lines in Japan

This article incorporates material from the corresponding article in the Japanese Wikipedia

Wikimedia Commons has media related toDosan Line.

• JR Shikoku official website(in Japanese)

• Dosan Line
• Lines of Shikoku Railway Company
• Rail transport in Kagawa Prefecture
• Rail transport in Tokushima Prefecture
• Rail transport in Kōchi Prefecture
• 1067 mm gauge railways in Japan
• Railway lines opened in 1889

• Articles with short description
• Short description matches Wikidata
• Articles containing Japanese-language text
• Commons category link from Wikidata
• Articles with Japanese-language sources (ja)