Sōtetsu Shin-Yokohama Line

JR through service trains will enter the Tōkaido Freight Line once leaving Hazawa Yokohama Kokudai Station, via the Tokyo-side of Yokohama-Hazawa Freight Station, then enter Yokosuka Line (Hinkaku Line) tracks near Tsurumi Station, and after that they'll share the same route as the Shōnan-Shinjuku Line, heading inbound towards Musashi-Kosugi, Ōsaki, Shibuya, Shinjuku, Ikebukuro, and head further north towards Ōmiya and Kawagoe, via the Saikyō and Kawagoe Lines.

JR and Sotetsu published a joint press release on 16 July 2019[3] which summarised the line's train operations. Trains will operate from Ebina on the Sotetsu Main Line, via Nishiya, Musashi-Kosugi, and enter the Saikyō Line at Ōsaki. Trains will mostly terminate at Shinjuku. In the morning rush hours, some trains go further north towards Musashi-Urawa, Ōmiya, Sashiōgi (where the Kawagoe Line depot is located), and as far as Kawagoe. A total of 46 round trips will be operated every day, with a rush-hour frequency of 4 trains per hour, and off-peak frequency of 2-3 trains per hour.

When the line opens, the fastest travel time would be 44 minutes between Futamatagawa and Shinjuku, 45 minutes between Yamato and Shibuya, and 36 minutes between Ebina and Musashi-Kosugi.[3]

•   Local (各停), stopping at all stations
•   Limited Express (特急), stopping at Ebina, Yamato, Futamatagawa, Nishiya, Hazawa Yokohama Kokudai and all stations on the JR Lines
  • However, when Limited Express trains are on the JR line, they are displayed as Local instead.

With this, Sōtetsu has already began upgrade works for its 12000 series trainsets, with the ATACS system used on the Saikyō Line being installed. JR East is also undergoing upgrade works on its E233-7000 series trainsets, to enable compatibility with the Sōtetsu Line.

Past proposals also suggested Sōtetsu trains to operate through services with the Ueno-Tokyo Line, towards the Utsunomiya, Takasaki and Jōban Lines. This requires trains to cross over level junctions to enter Tōkaido Line tracks near Tsurumi or Shinagawa (or somewhere in between), which would possibly undermine the high density train operations in this section, if no dedicated grade separation is built. Thus the idea was scrapped due to these difficulties.

Tōkyū through service trains will enter the Tōkyū Tōyoko Line near Hiyoshi, and heads towards Shibuya or Meguro (via Tōkyū Meguro Line).

Regarding the Tōyoko Line, it has not been announced whether Tokyo Metro Fukutoshin Line trains (and beyond that, the Seibu Yūrakuchō & Ikebukuro Lines and the Tōbu Tōjō Line) will operate through services with the Sōtetsu Line. Thus, it is unclear whether Sōtetsu trains can go beyond Shibuya through the Tōyoko Line.

Next, regarding the Meguro Line, it has been proposed that the Sōtetsu Tōkyū Link Line operate 14 trains per hour during rush hours, with 4 heading to the Tōyoko Line, and 10 heading to the Meguro Line. Meguro-bound Sōtetsu trains will operate through services not only to the Meguro Line, but also the Toei Mita Subway Line.

Currently, aside from JR East and Tōkyū, only Toei has advanced its plans to operate through services between the Sōtetsu Line and the Mita Subway Line.[4] In 2016, Toei announced that its 13 6300 series trainsets (1st and 2nd batch) would be replaced, and in 2019 9 new trainsets compatible with the Sōtetsu Line would begin service, with more trainsets to be produced until 2021.[5] In 2018, they ramped up their plans and announced that 13 new trainsets with the same designation numbers as the 13 that are replaced will be introduced to service.[6] These new models will be in 8-car formation,[7] made by Kinki Sharyo.[8] Meanwhile, the 3rd batch of 6300 series trainsets will continue their service on the Mita Line, but they will still be upgraded to enable compatibility with the Sōtetsu Line, by introducing digitized communications equipment and the ATS-P system.[9] With Mita Line trainsets extending to 8-cars, Sōtetsu is undergoing preparations to enable compatibility with 8-car trains.[10] On the other hand, Sōtetsu has also introduced its 20000 series which is to be used in Tōkyū through services, and has been in service since February 2018. The 20000 series will be produced in 10-car sets and 8-cars, with the 10-car sets not entering the Tōkyū Meguro Line and the Toei Mita Line.[11] Moreover, the 20000 series is not intended to be used on JR through services.