Tōkyū Shin-Yokohama Line

The line forms the Tōkyū half of the Sōtetsu–Tōkyū Link Line, the second-phase construction section of the Kanagawa Eastern Line, a plan promoted by the Japan Railway Construction, Transport and Technology Agency (JRTT) to improve rail connectivity in Kanagawa. Together with the Sōtetsu Shin-Yokohama Line it was the first case in the Kantō region of two different major private railways being joined directly without a subway operator in between. As with the Tōkyū Tamagawa Line, the company put its own name into the route title rather than calling it simply the 'Shin-Yokohama Line'; this was Tōkyū's second line to do so, and its through-partner the Sōtetsu Shin-Yokohama Line likewise carries an operator abbreviation in its name.

Planning milestones accumulated over several years. On 13 December 2018 the route name 'Tōkyū Shin-Yokohama Line' was announced for the Shin-Yokohama–Hiyoshi section. On 27 January 2022 the operators confirmed a March 2023 opening together with the through-running arrangements that would tie the line into the Sōtetsu, Tōkyū, Tokyo Metro, Toei and Tōbu networks. A rail-fastening ceremony was held at Shin-Yokohama on 22 July 2022; station numbering, using the route symbol 'SH', was settled on 16 September 2022; and the definitive station names were fixed on 21 October 2022. Familiarisation test running began on 3 November 2022, the opening timetable outline was published on 24 November 2022, and on 16 December 2022 the opening date was formally announced as 18 March 2023.

Almost the entire line is underground, with only Hiyoshi at ground level and no level crossings anywhere on the route. From Shin-Yokohama trains pass through the 3,304-metre Shin-Yokohama Tunnel, dipping beneath the Tsurumi River, before reaching the underground station of Shin-Tsunashima; they then run through the 1,357-metre Tsunashima Tunnel and climb to the half-underground terminus at Hiyoshi. The descent from the Tsunashima Tunnel toward ground-level Hiyoshi includes a 37-per-mille gradient that exceeds the 35-per-mille ceiling set by Japan's railway technical-standards ordinance; it was permitted because braking calculations showed a train could still stop within the regulatory 600 metres. The infrastructure is owned and maintained by JRTT, which Tōkyū pays for its use, and trains are based at Tōkyū's Motosumiyoshi depot.

The line opened as scheduled on 18 March 2023, a completion ceremony having been held at Shin-Yokohama on 5 March. From the first day, trains ran through services in both directions: from Shin-Yokohama via the Sōtetsu Shin-Yokohama Line onto the Sōtetsu Main and Izumino lines, and from Hiyoshi via the Meguro Line onto the Toei Mita Line or the Tokyo Metro Namboku Line and Saitama Rapid Railway, or via the Tōyoko Line onto the Tokyo Metro Fukutoshin Line and Tōbu Tōjō Line. Shin-Yokohama, jointly operated by Tōkyū and Sōtetsu, became the first station on either company's network to connect directly with the Shinkansen. One-man operation began on the new line and the Tōyoko Line at opening, and platform screen doors were in use from the first day.

Although the line's formal starting point is Shin-Yokohama, trains toward Shin-Yokohama are treated as 'down' services and those toward Hiyoshi as 'up'. Almost no trains run only within the line: services either head south through Shin-Yokohama onto the Sōtetsu network or north through Hiyoshi onto the Meguro or Tōyoko lines, with only a couple of within-line workings each day. Two service types operate, express and local, the local category being confined to Meguro Line through-trains; both call at all three stations on the Tōkyū Shin-Yokohama Line. A premium-fare add-on applies to the Shin-Yokohama–Shin-Tsunashima section, while no surcharge is levied between Shin-Tsunashima and Hiyoshi so that fares from the Shibuya and Meguro directions match those to neighbouring Tsunashima.

In the years after opening, services were adjusted. The line's first timetable revision came on 16 March 2024, adding an early-morning Meguro Line local and increasing daytime Meguro Line through-services from six to eight trains per hour, while stop positions at Hiyoshi had been shifted toward the Shin-Yokohama side on 20 January 2024. In October 2025, after a collision and derailment at Kajigaya on the Den-en-toshi Line was traced to a signalling-configuration error, Tōkyū found the same kind of design fault at two places within Shin-Yokohama Station; the affected signalling was repaired by 20 October 2025. New departure-warning sounds were introduced on Tōyoko Line services, including those of the Tōkyū Shin-Yokohama Line, from 1 November 2025. By financial year 2024, Shin-Yokohama was the line's busiest station, with a daily average of about 87,976 boarding and alighting passengers.

• 201813 December: the route name 'Tōkyū Shin-Yokohama Line' is announced for the Shin-Yokohama–Hiyoshi section.
• 202227 January: a March 2023 opening is announced, together with through-running plans linking the Sōtetsu, Tōkyū Meguro/Tōyoko, Toei Mita, Tokyo Metro Namboku/Fukutoshin, Saitama Rapid and Tōbu Tōjō lines.
• 202222 July: a rail-fastening ceremony is held at Shin-Yokohama Station.
• 202216 September: station numbering is decided, with the route symbol 'SH'.
• 202221 October: the definitive station names (Shin-Tsunashima, Shin-Yokohama) are fixed, replacing the provisional names.
• 20223 November: familiarisation test running begins, continuing until the March 2023 opening.
• 202216 December: the opening date is formally announced as 18 March 2023.
• 20235 March: a completion ceremony is held at Shin-Yokohama Station.
• 202318 March: the Tōkyū Shin-Yokohama Line opens between Shin-Yokohama and Hiyoshi; through-running with the Sōtetsu, Meguro and Tōyoko networks and one-man operation begin, and platform screen doors enter use.
• 202420 January: train stop positions at Hiyoshi Station (including the Meguro Line) are shifted toward the Shin-Yokohama side.
• 202416 March: the line's first timetable revision since opening adds an early-morning Meguro Line local and raises daytime Meguro Line through-services from six to eight trains per hour.
• 202510 October: following a collision and derailment at Kajigaya on the Den-en-toshi Line caused by a signalling-configuration error, Tōkyū reports the same kind of design fault at two places within Shin-Yokohama Station; the signalling is repaired by 20 October 2025.
• 20251 November: new departure-warning sounds are introduced progressively on Tōyoko Line services, including those of the Tōkyū Shin-Yokohama Line.