>>2049658
>saitama rapid railway
Japan has these sort of 5~10 year plans for railways.
This was proposed first in 1972, but Saitama at that time wasn't really all that populated and it wasn't a very cost effective line. So it was scraped.
It was revised in 1985 as projected numbers put Eastern Saitama and Northwest Chiba as big bottleneck with increasingly heavy rushhours. With the situation worsening over time.

This report envisioned several projects. This is whats basically the groundwork for todays Tokyo. Almost all lines proposed were built.

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Joban New Line run by JNR
Unamed Adachi Raiway that became Nippori-Toneri Liner as replacment for incredibly overcrowded buses. It stipulated a "medium capacity system" not full size trains trains.
Saikyo Line Extentions to Takasaki Line
New Subway that would become the Asakusa Line
New Subway that would become the Mita Line
New Subway that would become the Hanzmon LIne
New Subway that would be a loop one, downgraded to Oedo Line
New Subway that would become the Fukutoshin Line
A line conencting Chiba New Town to the Airport became the Hokuso Line
Keikyu Airport Line extention to Haneda

So this document is the origin of all the lines you mentioned.

This document was so compelling and sort of drove public opinion that most local governments tried to get it done at any cost.

In the case of the Oedo line the cost was a massive downgrade of the line in both capacity and size. It's loud small and deep. By far the worst subway in Tokyo. I had to ride it with open windows during covid and my ears will never recover.