Namboku Line (Tokyo Metro)

Planning

Although the line was originally approved in 1962 as Line 7 (Meguro – Iikurakatamachi – Nagatacho – Ichigaya – Komagome – Oji – Akabanecho), construction did not begin until 1986.^[2]

Based on this proposal, the Teito Rapid Transit Authority (TRTA) applied for a license to construct Local Railway Line No. 7 between Kami-Osaki (Meguro) and Akabane-cho (present-day Kirigaoka), a distance of 22.5 km. Although the terminus designated in the urban planning route was Iwabuchi-cho (present-day Akabane-Iwabuchi), the application extended the proposed line to Kirigaoka (then known as Akabane-cho 5-chome) to allow for the operation of a spur line to a train depot for passenger services.^[2] However, on June 4, 1964, the Tokyo Metropolitan Government also applied for a license to construct Local Railway Line No. 7 between Meguro and Akabane, a distance of 21.0 km. This resulted in a competitive situation between the two proposed routes.

In the 1972 Report No. 15 of the Urban Transportation Council, the proposed extension toward Saitama Prefecture, which had previously been designated for future consideration, was revised to run between the central part of Kawaguchi and the eastern part of Urawa.^[2] Subsequently, the 1985 Report No. 7 of the Transportation Policy Council called for the section between Meguro and Kiyoshōkō-mae (present-day Shirokane-takanawa Station) to be shared with Line 6 (the Toei Mita Line). The proposed route within Saitama Prefecture was also revised to run via central Hatogaya, Higashi-Kawaguchi, and onward to eastern Urawa. Of these proposed routes, the section between Meguro and Akabane-Iwabuchi was progressively opened as the Namboku Line. The section between Akabane-Iwabuchi and Urawa-Misono subsequently opened as the Saitama Rapid Railway Line.^[2]

Although the line had been planned since the 1960s, the project was temporarily suspended due to issues surrounding the planned train depot in Nishigaoka, Kita, Tokyo. On April 20, 1984, 22 years after the initial license application, the full-line railway construction license was finally granted. Construction began in 1986, and the line opened in stages beginning in 1991, with the entire line completed in 2000. As a relatively late addition to Tokyo's railway network, the Namboku Line is characterized by its generally deep underground stations.^[2]

Under the original construction plan, the first phase was to cover the section between Komagome and Akabane-Iwabuchi, while the second phase was to cover the section between Meguro and Komagome. However, the second phase was subsequently divided into two sections: Tameike-Sanno–Komagome (Phase 2-1) and Meguro–Tameike-Sanno (Phase 2-2). As a result, construction was ultimately carried out in three sections.

Construction of the first-phase section proceeded without major delays. The second-phase sections, however, were delayed by the excavation of archaeological sites, including Edo-period remains discovered between Tameike-Sanno and Iidabashi,^[2] as well as opposition and NIMBYs from local residents, particularly in the vicinity of Shirokanedai Station. Consequently, the planned date for completion of the entire line was substantially postponed, from September 1995 to September 2000.^[2]

Opening

The first segment from Komagome to Akabane-Iwabuchi opened on 29 November 1991.

The line initially operated with four-car EMUs. Upon its extension to Yotsuya in March 1996, the formations were extended to six cars. On 1 April 2022, eight-car trains began operating on the line.^[3]

The extension to Tameike-Sannō was completed in September 1997, and the last stretch from Tameike-Sanno to Meguro was completed on 26 September 2000, when through service to the Tokyu Meguro Line started.^[4] Through service with the Saitama Rapid Railway Line commenced when it opened in March 2001 and accommodated traffic to and from Saitama Stadium during the 2002 World Cup. Although the Saitama Line is more or less a northern extension of the Namboku Line, it nevertheless remains a private entity to which the Namboku Line offers through services with.

The Namboku Line was inherited by Tokyo Metro after the privatization of the Teito Rapid Transit Authority (TRTA) in 2004.^[5]

Effective the timetable revision on 18 March 2023, through services onto the Sagami Railway commenced courtesy of the Tokyu and Sotetsu Shin-Yokohama Line.^[6] Most southbound services past Hiyoshi continue as far south as Shin-Yokohama and Ebina.

Future plans

On 28 January 2022, Tokyo Metro announced that a 2.5 km (1.6 mi) spur line from Shirokane-takanawa to Shinagawa would be built.^[7] The extension is expected to cost ¥131 billion (2021) (equivalent to ¥142.46 billion or US$941.14 million in 2024)^[8] and scheduled to begin revenue service in the mid-2030s. It is intended to increase connections to and from the Chūō Shinkansen, which is scheduled to open for service as early as 2035.