| Heavy rail|
93.3 km (58.0 mi)
| Chiba Station, Awa-Kamogawa Station|
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 Ōami-Shirasato, 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.
Sotobō Line Wikipedia
In addition to local services, limited express and Rapid ("Commuter 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 / Commuter 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)
Local trains stop at every station.
255 series EMUs (Limited express Wakashio)
E257-500 series EMUs (Limited express Wakashio)
209-2000/2100 series 4/6-car EMUs (Sotobō Line local services)
211-3000 series 5-car EMUs (Sotobō Line local services since 21 October 2006)
E217 series 11+4-car EMUs (Sōbu Line (Rapid) through services as far as Kazusa-Ichinomiya)
E233-5000 series 10-car EMUs (Keiyō Line through services as far as Katsuura)
113 series EMUs (Sotobō Line local services, until 2011)
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.Mobara Station: The Mobara Town Council operated a 9 km, 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 of 1,067 mm (3 ft 6 in) gauge line was opened as far as Okuno between 1930 and 1933, the first 6 km 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, 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.