This is the first of a series of track switches to be implemented in conjunction with a large-scale improvement project at the station. Prior to this, Minami-Sunamachi Station was opened to the press on May 7.
As already announced, Tokyo Metro will suspend service all day between Toyocho and Nishi-Kasai on the Tozai Line between May 11 and 12, and conduct track switching work in front of and behind Minami-Sunamachi Station.
What is the major improvement project of Minamisunamachi Station?
The Tozai Line is one of the most congested lines not only in Tokyo Metro but also in the entire Tokyo metropolitan area, and naturally, the intervals between trains during rush hours are short.
In addition, Minamisunamachi Station itself has seen a significant increase in use since the beginning of the 2000s: the growth between 1990 and 2000 was about 10%, but between 2000 and 2019, the growth was about 50%. The station’s daily ridership will reach 54,000 in FY2022.
As the number of passengers increases, the time required to get on and off the train will also increase, but the longer the stop time, the more the following train will be held up. This would lead to delays that would spread out like a cascade, which is not good from the standpoint of stable transportation. In addition, if a large number of passengers are concentrated in cramped concourses and ticket gates, the flow of people will also be slowed down.
Therefore, it was decided to construct an additional platform and track for the line going toward Nakano (Line B). (The common terms “up line” and “down line” do not ring a bell in subways that run through the center of Tokyo. ) Therefore, the terms “A line” and “B line” have been used since the days of the Teito Rapid Transit Company.
If there is only one platform and one track, trains can only depart and arrive one at a time in sequence. However, if there are two tracks, one platform can be used to handle passengers and depart while the other is used to accommodate the following train. This is the so-called alternating arrival and departure system, which is routinely used at Shinjuku Station on the JR Chuo Rapid Line and at major stations on the Tokaido Shinkansen Line.
The improvement work at Minamisunamachi Station will include widening the existing platform in conjunction with the addition of tracks and platforms. In addition, the current ticket gates at both ends of the station will be relocated and consolidated in the center of the station, and a wider concourse will be secured. This will facilitate the flow of passengers getting on and off at Minamisunamachi Station. The number of passages for automatic ticket gates is currently three for Nakano and five for Nishi Funabashi, but the new station will have seven passages.
In the next phase of switching work, Line A will be replaced with the current Line B. This will leave the current Line A empty. Since the current Line A will now be vacant, the tunnel will be expanded, Line A will be relocated to the north, and the platform will be widened (from 6m to 9m).
Then, in the final track switching work, Line A will be returned to its original position to complete the final form. This large-scale improvement work is scheduled for completion in FY2027. When the improvement work is completed, the station structure will be converted from a single island type with two lines to a double-island type with three lines. The middle track (now Line B) will be accessible from both Lines A and B, both front and rear.
An interesting feature of the Minami-Sunamachi Station construction is that a new tunnel structure is being built around the existing tunnel structure. This was done to allow construction work to be carried out while trains continue to operate, and to allow for platform expansion and track relocation. However, the ground at the site is not solid, so extra care was required to prevent deformation of the existing tunnel frame.
On the Tozai Line, improvements are underway not only at Minamisunamachi Station, but also between Iidabashi and Kudanshita Stations, and at Kayabacho Station, including the extension of platforms, change of stop locations, and addition of stairs and escalators.
© Source travel watch
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