Tōzai Line (Tokyo Metro)

Early years

The original plan for what is now the Tōzai Line was included in a report by the Tokyo City and Area Transportation Research Committee (東京市内外交通調査委員会), which was established within the Ministry of Home Affairs in 1917. The proposal outlined a route connecting “Ikebukuro – Takadanobaba – Iidabashi – Otemachi – Susaki”.

In 1920, a construction patent for this route was granted to the Tokyo Railway (東京鉄道). However, following the Great Kantō Earthquake of 1923, the patent was revoked along with those for other planned lines because construction had not yet commenced.

The route license for the Tōzai Line originates from the six municipal subway lines planned by Tokyo City, the predecessor of today’s Tokyo special wards, prior to World War II. The license was granted on May 16, 1925, under Ministry of Home Affairs Notification No. 56 of 1925 (大正14年内務省告示第56号).^[4][5]

The present Tōzai Line corresponds to the former Line 5, which was authorized as a 14.2-kilometer route running from “Ikebukuro – Waseda – Iidamachi – Hitotsubashi – Tokyo – Eitaibashi – Susaki”.^[5] As part of the initial phase of the Tokyo Municipal Subway project, Tokyo City planned to begin construction on Line 3 between Shibuya and Sugamo and on Line 5 between Ikebukuro and Susaki. However, due to the city’s substantial public debt and concerns over deteriorating finances, the Ministry of Home Affairs and the Ministry of Finance opposed the project, and construction approval was not granted.^[4]

Following this setback, no further construction plans were pursued, and the Teito Rapid Transit Authority, commonly known as the Eidan Subway, was subsequently established. In 1941, all subway route licenses held by the Tokyo municipal government were transferred to the Teito Rapid Transit Authority in exchange for compensation.^[4]

By contrast, the section corresponding to the present-day Tōyōchō to Nishi-Funabashi segment was originally licensed to the Tokyo Narishiba Electric Railway (東京成芝電気鉄道) prior to World War II. The application was approved in 1927, with the eastern terminus Tōyōchō designated as Higashi-hirai. However, this license ultimately expired in 1940 after construction failed to proceed.

Post-war construction

The Tōzai Line was planned by a review committee of the then Ministry of Transportation in 1962 and numbered Line 5. Its name literally means "East-West Line", and it was primarily planned to relieve traffic on the busy Sōbu Main Line as well as provide a straight crosstown connection through north-central Tokyo. Although this corridor is also served by the Tokyo Metropolitan Bureau of Transportation (Toei) Shinjuku Line and JR Keiyō Line, the Tōzai Line continues to operate beyond capacity due to its accessibility to other lines, as well as to growing condominium developments in eastern Tokyo.

The Takadanobaba to Kudanshita section opened in 1964,^[6] and the remainder opened in stages until its completion in 1969. Through service with the then Japanese National Railways (today part of the JR Group) – a first for a Tokyo subway line – began in 1969 connecting the Chūō and Sōbu lines. This is a rare situation in Tokyo, as the only other subway line with through services onto JR lines is the Chiyoda Line.

Due to a surge in ridership on the Tōzai Line, the Teito Rapid Transit Authority (TRTA) introduced 12 new-build 5000 series cars and transferred 50 from the Chiyoda Line in 1981 in an effort to increase capacity on the line. Rapid residential development in the Urayasu and Kasai areas further increased demand. In response, TRTA introduced rapid trains that ran non-stop between Nishi-Funabashi and Toyocho stations, and stopped at every station west of Urayasu, in November 1986.^[7]

The Tōyō Rapid Railway Line, effectively an eastward extension of the line, opened in 1996. It nevertheless remains a private entity to which the Tōzai lines offers through services.

Chronology

• March 16, 1966: The line is extended at both ends. It now runs between Nakano and Takebashi.
• April 28, 1966: Through service to the Chūō Line of JNR commences as far as Ogikubo.
• October 1, 1966: Takebashi to Ōtemachi section opens.
• September 14, 1967: Ōtemachi to Tōyōchō section opens.
• March 29, 1969: Tōyōchō to Nishi-Funabashi section opens and Rapid service begins (non-stop between Tōyōchō and Nishi-Funabashi).
• April 8, 1969: Through service on the Chūō Line is extended to Mitaka, and through service begins on the Sōbu line to Tsudanuma.
• April 8, 1972: Through service on the Sōbu Line is withdrawn except during rush hours.
• 1975: Another type of Rapid service is introduced, calling at Urayasu between Tōyōchō and Nishi-Funabashi.
• October 1, 1979: Nishi-Kasai station opens.
• March 27, 1981: Minami-Gyōtoku station opens.
• 1986: Commuter Rapid service is introduced, running non-stop between Urayasu and Nishi-Funabashi.
• (April 1, 1987: JNR is privatised. The Chūō and Sōbu lines become the property of JR East.)
• 1996: The Rapid service that runs non-stop between Tōyōchō and Nishi-Funabashi ceases.
• April 27, 1996: Tōyō Rapid Line opens between Nishi-Funabashi and Tōyō-Katsutadai. Through service begins.
• January 22, 2000: Myōden station opens.
• April 1, 2004: Teito Rapid Transit Authority (TRTA or Eidan) becomes Tokyo Metro.^[8]
• November 20, 2006: Women-only cars are introduced during morning rush hours.

Present

Tōzai Line trains are 10-car formations of 20-meter (65 ft 7 in)-long cars, with four doors per side and longitudinal seating. The maximum operating speed is 100 km/h (62 mph). Newer trains feature wide doors to allow for faster boarding times.

• Tokyo Metro
  • 05/05N series (since 1988)
  • 07 series (since 2006) (transferred from Yūrakuchō Line)
  • 15000 series (since 2010)
• Tōyō Rapid Railway
  • 2000 series (since 2004)
• East Japan Railway Company (JR East)
  • E231-800 series (since 2003)

• 
  Tokyo Metro 05 series
• 
  Tokyo Metro 05N series
• 
  Tokyo Metro 07 series
• 
  Tokyo Metro 15000 Series
• 
  Toyo Rapid 2000 series
• 
  JR East E231-800 series

Past

• Tokyo Metro
  • 5000 series (from 1964 until 2007)
  • 8000 series (from 1987 until 1988, temporary, built for Hanzōmon Line)
• JR East
  • 301 series (from 1966 until 2003)
  • 103-1000 series (from 1989 until 2003)
  • 103-1200 series (from 1971 until 2003)
• Tōyō Rapid
  • 1000 series (from 1996 until 2006)

• 
  5000 series with stainless steel body
• 
  5000 series with aluminium body
• 
  8000 series
• 
  JR East 301 series in February 2003
• 
  JR East 103–1200 series
• 
  Tōyō Rapid 1000 series in September 2006