Den-en-toshi Line

The Den-en-toshi Line is a major commuter line operated by the private railway operator Tokyu Corporation and connecting south-western suburbs of Tokyo and neighboring Kanagawa Prefecture, with its western terminus of, to a major railway junction of western downtown Tokyo,. At Shibuya, nearly all the trains continue on the Tokyo Metro Hanzomon Line. With a route length of, it is the longest railway line operated by Tokyu Corporation.
The line's color on maps and station guides is green, and stations carry the prefix "DT" followed by a number.

History

Prewar predecessors

On 6 March 1907, the Tamagawa Electric Railway opened the first section of an interurban line between Shibuya and what is now, using gauge. The line was called the Tamagawa Line and is not to be confused with today's Tokyu Tamagawa Line. The branch from Sangen-Jaya Station opened on 18 January 1925.

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 19 March 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.

Accidents and incidents

On 5 October 2025, around 11:00 p.m, the rear car of an out-of-service Tokyu 5000 series was struck by an oncoming Shibuya-bound Tokyu 2020 series train as it was entering a layover track. The impact caused the out-of-service train to derail. It was hosting a trainee driver under instruction and had reportedly stopped slightly ahead of its designated position, leaving part of the train protruding onto the active track. The collision caused visible damages but no serious injuries were reported among the 149 passengers on board the moving train or among the crew on the stationary train. Following the collision, the operator disclosed that a "signal-setting error" had persisted for years since maintenance works were carried out in 2015. Following the collision, normal services on the Den-en-toshi Line were partially suspended for a few days, with nearby lines such as the Ōimachi Line and the Tokyo Metro Hanzōmon Line also experiencing service suspensions and disruptions. This was caused by the collided trains blocking the trains in train depot from exiting. Tokyu Railways deployed maintenance crews to remove the derailed 5000 series car and to inspect track and signal equipment near Kajigaya Station. To prevent similar accidents, Tokyu Railways inspected 33 other stations with similar track layout.

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, Tobu Isesaki Line, and Tōbu Nikkō Line. At rush hour, an inbound train arrives as frequently as every 2 minutes 10 seconds.

Service types

The following three types of service are operated on the line.
; Local
; Semi-Express
; Express

Through trains to Ōimachi Line

On weekends, two seven-car express trains per days are operated to/from and. Also, a few trains are operated through to/from the Tōkyū Ōimachi Line to utilize forwarding operations to/from Saginuma depot, up to Ōimachi in the mornings, and down to in the late evenings. These formations are 7-car sets, unlike the 10-car trains normally used on the line. A few express trains during the holidays also serve from in the mornings, down in the evenings.