The is a Japanese railway line operated by the East Japan Railway Company (JR East) in Japan. It connects Tokyo with the east coast of Chiba Prefecture, passing through the cities of Funabashi, Chiba, and Chà Âshi. Its name derives from the old provinces of the area which it serves: Musashi (), Shimà Âsa () and Kazusa (). Its official line color is navy.
Formally, the SÃ Âbu Main Line refers to the line from Tokyo to .
However, informally, the character of the line changes at Chiba. The more urbanized section west of Chiba is informally, but commonly, called the SÃ Âbu Line(, ) without using "Main". The "Main Line", in popular usage, refers to the more rural section east of Chiba.
Route maps, signs at stations, in trains, and the vocal announcements all maintain this distinction: with Main for the eastern rural section; without Main for the western frequent travel zone.
Local trains run between Ochanomizu and Chiba Station and are called the Chà «à Â-Sà Âbu Line (, ) or Sà Âbu-Local Line (, ).
Rapid trains are also operated from Tokyo Station to Chiba Station and use different tracks from the local service trains. These Rapid trains sometimes continue east on the Main Line after reaching Chiba. In reverse, Sobu Main Line trains also sometimes continue west on the Rapid Line after reaching Chiba, some even go on the Yokosuka Line after Tokyo. The rapid trains are called SÃ Âbu Rapid Line (, ).
For the most part, Rapid and Local trains run parallel with each other, except when they reach Kinshicho, where Sà Âbu Line Local trains continue onto the Chà «à  Line at Ochanomizu via Akihabara, while Sà Âbu Line Rapid trains head to Tokyo, with most of them continuing onto the Yokosuka Line.
For more details of services west of Chiba, see the relevant articles for the Local and Rapid Lines.
The section east of Chiba, from Chiba to Chà Âshi, is commonly known as the Sà Âbu Main Line (, ). The aforementioned Sà Âbu Rapid Line through service trains would terminate at Sakura or Narutà  on the Main Line, or go on the Narita Line after Sakura for Narita Airport or Kashima-Jingu. Aside from that, there are also local trains running along the entire section, from Chiba to Chà Âshi.
The Narita Express to Narita Airport Station and the Ayame to use the SÃ Âbu Main Line for their journey.
Shiosai, also a Limited Express service, which operates from Tokyo Station to Chà Âshi, also uses this line.
Here is a list of stations within this section. ([ ] denotes the Ochanomizu - Kinshicho section.) Tokyo - Shin-Nihombashi - Bakurochà  [ Ochanomizu - Akihabara - Asakusabashi - Ryà Âgoku - Kinshichà  ] Kameido - Hirai - Shin-Koiwa - Koiwa - Ichikawa - Moto-Yawata - Shimà Âsa-Nakayama - Nishi-Funabashi - Funabashi - Higashi-Funabashi - Tsudanuma - Makuharihongà  - Makuhari - Shin-Kemigawa - Inage - Nishi-Chiba - Chiba
For the connections of the line, see the route diagram.
From Chiba to Sakura, the section is double track; and from Sakura onwards to Choshi, the section is single track.
All stations on this section of the line are in Chiba Prefecture.
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Initially, the line was constructed by a private company, Sà Âbu Railway(, ). It opened the first service sections, between Ichikawa and Sakura on July 20, 1894, and extended to Tokyo City. In December of the same year, Honjo(, now ) was opened, and in 1904, on the east bank of Sumida River, Ryà Âgokubashi (, now ) became a terminal of this line. The access routes to the west, to Tokyo City, were tramways for passengers and ships for freight. From Sahara to the east, this line reached another terminus, Chà Âshi in 1897.
The line was nationalized in 1907 under the Railway Nationalization Act, and was double-tracked from Ryà Âgokubashi to Chiba the next year. The predecessor of the Japanese National Railways (JNR) planned to connect with other lines inside Tokyo. In 1932, a new passenger line was opened from Ochanomizu to Ryà Âgoku (with new platform besides the original terminal facility), and a frequent service of EMUs commenced. Electrification to Chiba was completed in 1935, and local trains have run through from the Chà «à  line since then. But, except for a few trains, no rapid service was operated on this line, and the passengers had to use the local train, or its rival, Keisei Electric Railway.
On March 10, 1945, the Bombing of Tokyo caused casualties estimated at 70,000âÂÂ100,000, and destroyed stations of the line. During the last days of World War II in 1945, the Imperial Japanese Army thought the US Army would attempt a landing operation, "Operation Coronet", on Kujà «kuri Beach, and transferred troops on the Sà Âbu Main Line.
Between Chiba and Chà Âshi, in the rural area of Chiba Prefecture, steam traction was used until recently. Fish and soy sauce from Chà Âshi were major freight items. Because Tokyo was close, JNR did not provide rapid or express trains from Ryà Âgoku to Chà Âshi until 1958. JNR operated tourist trains from Ryà Âgoku to the seaside resorts on the coast from the 1950s.
In the 1960s, JNR started the Five-Destination Operation (, ) to steeply increase commuter demand, and it determined that a new rapid line would be constructed from Tokyo Station to Chiba. A new underground line from Tokyo to Kinshichà Â, and a four-tracked section to Tsudanuma were opened in 1972, and the operator began frequent rapid services from Tokyo to Chiba. The line was managed by the East Japan Railway Company (JR East) from 1987. The parallel Keiyà  Line was opened closer to the coast in 1990. It was first constructed for freight services but later to carry passengers.
To the east of Chiba, electrification reached Chà Âshi in 1974, and Limited Express Shiosai has been operated from the underground Tokyo Station since 1975. Freight services from Chà Âshi ceased in 1986, just before the privatization of JNR, and regular passenger trains stopped using the Ryà Âgoku terminal platforms in 1988. JR East started a new airport train, the Narita Express in 1991. Rapid urbanization around Chiba Station made this section important for commuter traffic, for the city of Chiba, and for Greater Tokyo.