Sotobō Line

Sotobō Line
Sotobō Line
	Sotobō Line Wakashio limited express service, November 2017
Overview
Locale	Chiba Prefecture
Termini	Chiba; Awa-Kamogawa;
Stations	27
Service
Type	Heavy rail
Operator(s)	JR East
Depot(s)	Chiba
History
Opened	1896
Technical
Line length	93.3 km (58.0 mi)
Track gauge	1,067 mm (3 ft 6 in)
Operating speed	110 km/h (70 mph)
Route map
Route map

The Sotobō Line (外房線, Sotobō-sen) is a railway line in Japan operated by the East Japan Railway Company (JR East) adjacent to the Pacific Ocean, on the eastern (i.e., outer) side of the Bōsō Peninsula. It connects Chiba Station in Chiba to Awa-Kamogawa Station in Kamogawa, passing through Ōamishirasato, Mobara, Chōsei, Ichinomiya, Isumi, Onjuku, and Katsuura. The line is connected to the Uchibō Line at both ends. South of Kazusa-Ichinomiya is single track, and north of Kazusa-Ichinomiya is double track.

Sotobo Line

Legend

1 2 3		1: Keisei Chiba Line
		2: Chūō-Sōbu Line
		3: Sōbu Line (Rapid)
	0.0	Chiba (II) 1963–

		Chiba Monorail Line 1
		Keisei Chiba Station (II) 1958–

		Chiba Station (I) -1963
		Sōbu Main Line
		Keisei Chiba Station (I) -1958
		Chiba Monorail Line 2
		Hon-Chiba Station (I) -1958
		Chiba-Chūō
	1.4	Hon-Chiba (II) 1958–
		Keisei Chihara Line
		Keiyō Line
	3.8	Soga
		Keiyō Rinkai Railway Rinkai Main Line

		Uchibō Line

	8.8	Kamatori
	12.6	Honda
	18.1	Toke


		Toke Tunnel	881m


	22.9	Ōami (II)
		Ōami Station (I)
		Tōgane Line
	25.3	Nagata
	27.7	Honnō

	31.4	Shin-Mobara

			JASDF Mobara Airfield
		Mitsui Chemicals
		Nansō Line (defunct)
		Kazusa-Takashi Station
	34.3	Mobara
		Chōnan-Mobara Jinrikisha Rail Line
	38.9	Yatsumi
		Ichinomiya River
	43.0	Kazusa-Ichinomiya
		Fire balloon Site
	46.2	Torami
	49.3	Taitō
		Izumi River
	52.1	Chōjamachi
	53.7	Mikado
	55.6	Tōkai Station (closed)
		Isumi Railway Line
	57.2	Ōhara
		Isumi Kidō Jinrikisha Line
	60.5	Namihana
	65.4	Onjuku
	70.9	Katsuura
		Ubara Tunnel
	74.3	Ubara
		Okitsu Tunnel
	77.2	Kazusa-Okitsu
	80.5	Namegawa-Island
		Uchiura Tunnel
	84.3	Awa-Kominato
		Ōboiso Tunnel
	87.7	Awa-Amatsu
		Uchibō Line
	93.3	Awa-Kamogawa

Services

In addition to local services, limited express and Rapid services run on this line.

Limited Express Wakashio

Tokyo – (Keiyō Line) – Soga – Awa-Kamogawa

(some operate as all-stations "Local" services between Katsuura and Awa-Kamogawa

Rapid
- Kurihama – (Yokosuka Line) – Tokyo – (Sōbu Line (Rapid)) – Soga – Kazusa-Ichinomiya
- Tokyo – (Keiyō Line) – Soga – Ōami – Kazusa-Ichinomiya (some to/from Katsuura, or Narutō on the Tōgane Line)
  - Commuter Rapid services through to/from the Keiyō Line also used to operate, but they have been discontinued as of 16 March 2024.^[1]

Station list

Legend

● : All trains stop
(●) : Some trains stop
| : All trains pass

Notes

Local trains stop at every station.

Station	Japanese	Distance (km)	to/from Keiyō Line		to/from Sōbu Line (Rapid) and Yokosuka Line		Transfers	Location (in Chiba)
Station	Japanese	Distance (km)	Keiyō Line Rapid	Limited express Wakashio	Sōbu Line Rapid	Limited express Shinjuku Wakashio (Weekends only)	Transfers	Location (in Chiba)
Chiba	千葉	0.0			●	●	JO Sōbu Line (Rapid) (JO28) (some through services) JB Chūō-Sōbu Line (JB39) ■ Sōbu Main Line ■ Narita Line Chiba Urban Monorail Line 1, Line 2 KS Keisei Chiba Line (Keisei Chiba: KS59)	Chūō-ku, Chiba
Hon-Chiba	本千葉	1.4			●	\|
Soga	蘇我	3.8	●	●	●	●	JE Keiyō Line (some through services) ■ Uchibō Line
Kamatori	鎌取	8.8	●	\|	●	\|		Midori-ku, Chiba
Honda	誉田	12.6	●	\|	●	\|
Toke	土気	18.1	●	(●)	●	\|
Ōami	大網	22.9	●	●	●	●	■ Togane Line	Ōamishirasato
Nagata	永田	25.3	(●)	\|	\|	\|		Ōamishirasato
Honnō	本納	27.7	(●)	\|	\|	\|		Mobara
Shin-Mobara	新茂原	31.4	(●)	\|	\|	\|
Mobara	茂原	34.3	●	●	●	●
Yatsumi	八積	38.9	(●)	\|	\|	\|		Chōsei
Kazusa-Ichinomiya	上総一ノ宮	43.0	●	●	●	●		Ichinomiya
Torami	東浪見	46.2	●	\|		\|		Ichinomiya
Taitō	太東	49.3	●	\|		\|		Isumi
Chōjamachi	長者町	52.1	●	\|		\|
Mikado	三門	53.7	●	\|		\|
Ōhara	大原	57.2	●	●		●	■ Isumi Line
Namihana	浪花	60.5	●	\|		\|
Onjuku	御宿	65.4	●	●		●		Onjuku
Katsuura	勝浦	70.9	●	●		●		Katsuura
Ubara	鵜原	74.5		\|		\|
Kazusa-Okitsu	上総興津	77.2		(●)		●
Namegawa-Island	行川アイランド	80.5		\|		\|
Awa-Kominato	安房小湊	84.3		●		●		Kamogawa
Awa-Amatsu	安房天津	87.7		\|		\|
Awa-Kamogawa	安房鴨川	93.3		●		●	■ Uchibō Line (some through services)

Rolling stock

Local service

E131 series 2-car EMUs (since 13 March 2021)
209-2000/2100 series 4/6-car EMUs

Keiyō Line through service

Between Soga and Katsuura:

209-500 series 10-car EMUs
E233-5000 series 6+4-car and 10-car EMUs

Sōbu Line (Rapid) through service

Between Chiba and Kazusa-Ichinomiya:

E217 series 11+4-car EMUs
E235-1000 series 11+4-car EMUs (since 21 December 2020)

Wakashio Limited Express

255 series EMUs
E257-500 series EMUs

Former rolling stock

113 series EMUs (Sotobō Line local services, until 2011)
211-3000 series 5-car EMUs (Sotobō Line local services from 21 October 2006 to spring 2013)^[2]

History

Mobara handcar line

A former handcar converted with a petrol engine at Ohara

The Boso Railway opened the Chiba to Oami section in 1896, extending the line to Kazusa-Ichinomiya the following year and to Ohara in 1899. The company was nationalised in 1907. The extension to Katsuura opened in 1913, to Kazusa-Okitsu in 1927, and Awa-Kamogawa in 1929.

A new tunnel and associated deviation was opened at Toke in 1954 to improve the loading gauge of the line. The Chiba to Soga section was double-tracked between 1960 and 1963, extended to Nagata between 1972 and 1974, with CTC signalling being commissioned between Soga and Awa-Kamogawa in 1974. The line to Kazusa-Ichinomiya was double-tracked between 1980 and 1986, with the Onjuku to Katsuura section double-tracked in 1995, and the Torami to Chojamachi section the following year. The entire line was electrified in 1968, and freight services ceased between 1982 and 1987.

Former connecting lines

Mobara Station: The Mobara Town Council operated a 9 km (5.6 mi), 610 mm (2 ft) gauge handcar line to Tai Muko between 1909 and 1924. The council then decided to build a railway to connect to the Kominato Line. 12 km (7.5 mi) of 1,067 mm (3 ft 6 in) gauge line was opened as far as Okuno between 1930 and 1933, the first 6 km (3.7 mi) following the handcar line alignment. Poor patronage and economic circumstances led to the line being closed in 1939.
Ohara Station: The Chiba Prefectural Government opened a 16 km (9.9 mi), 610 mm (2 ft) gauge handcar line to Otaki in 1912. A railcar was converted to petrol engine power in 1922. The line closed in 1927 to allow for the construction of the Isumi Line, which opened on the same alignment in 1930.

Accidents

On 8 May 2020, at 3:55 pm, the front carriage of a local service derailed between Awa-Kamogawa and Awa-Amatsu stations. Around 20 passengers and crew were on board the train (a 209 Series) when it derailed. One person was taken to a hospital.^[3]

References

^ "京葉線で通勤快速列車の運転終了" [Commuter Rapid service on Keiyo Line ended]. Japan Railfan Magazine Online (in Japanese). Japan: Koyusha Co., Ltd. 16 March 2024. Retrieved 15 April 2024.
^ "10/21, 房総211系, 営業運転開始" [Boso 211 series enter service]. Japan Railfan Magazine (in Japanese). Vol. 47, no. 549. Japan: Koyusha Co., Ltd. January 2007. p. 179.
^ "ほぼ直線…外房線先頭車両が脱線原因は？". headlines.yahoo.co.jp (in Japanese). 8 May 2020. Retrieved 9 May 2020.

External links

JR East Sōbu and Bōsō area route map

[CRended-1] "京葉線で通勤快速列車の運転終了" [Commuter Rapid service on Keiyo Line ended]. Japan Railfan Magazine Online (in Japanese). Japan: Koyusha Co., Ltd. 16 March 2024. Retrieved 15 April 2024.

[railfan549-2] "10/21, 房総211系, 営業運転開始" [Boso 211 series enter service]. Japan Railfan Magazine (in Japanese). Vol. 47, no. 549. Japan: Koyusha Co., Ltd. January 2007. p. 179.

[3] "ほぼ直線…外房線先頭車両が脱線原因は？". headlines.yahoo.co.jp (in Japanese). 8 May 2020. Retrieved 9 May 2020.

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