text: Tama Den-En-Toshi Plan In 1953, Tokyu Group president Keita Gotō unveiled a "new town" planning scheme called the South-Western Area Development Plan. He envisioned new railway line and freeway and large, clean houses for commuters working in Tokyo. The railway line would become the Tama Den-En-Toshi Line and the expressway the Tōmei Expressway. The parts of the new line completely overlaps the Tamagawa Line and the project is known as the Shin-Tamagawa Line or "New Tamagawa Line" which runs in an underground alignment under the old interurban line. The Tamagawa Line was closed in 1969 in anticipation for the opening of the Shin-Tamagawa Line, with the remaining branch line of the Tamagawa Electric Railway split off into the present Tokyu Setagaya Line. The underground Shin-Tamagawa Line opened a few years later in 1977, completely replacing the closed interurban line. Upon opening it was treated as a separate line from the Ōimachi Line connecting to said line at Futako-Tamagawa.
  Development of the line
  In 2000, Tama Den-En-Toshi Line as depicted today was created by merging the Shin-Tamagawa Line and the section of the Ōimachi Line west of . Trains through servicing into the Tokyo Metro Hanzōmon Line was extended beyond  into Isesaki Line and Nikkō Line of Tobu Railway on March 19, 2003.
  Tokyu has expanded the line to four tracks from Futako-Tamagawa to Mizonokuchi; most trains of the Ōimachi line run through this section to Mizonokuchi, with some local trains making the intermediate stops. This service began in June 2009, postponed from fiscal 2007. Ōimachi line trains, which are 5- or 7-car sets, will then run between  and Mizonokuchi.
  Operation
  Nearly all trains on the Den-en-toshi Line are operated through to/from the Tokyo Metro Hanzomon Line using Tokyu, Tokyo Metro, and Tobu Railway 10-car EMUs. Around half of them continue beyond , the terminus of the Hanzomon Line, to the Tobu Skytree Line (Kita-Koshigaya Station, Kita-Kasukabe Station and Tōbu-Dōbutsu-Kōen Station), Tobu Isesaki Line (Kuki Station), and Tōbu Nikkō Line (Minami-Kurihashi Station). At rush hour, an inbound train arrives as frequently as every 2 minutes 10 seconds.