Seibu 40000 series
Data (as of 22 Feb 2026)
| Status: | Least Concern |
| Constructed in: | 2016- |
| Number built: | 240 |
| Registered: | 240 |
History
The 40000 series was introduced in advance of commencing S-Train services (Kotesashi - Toyosu on weekdays, Seibu-Chichibu - Motomachi Chukagai at weekends), as well as to replace 9000 series on the Ikebukuro Line. There are two groups: "dual-seat" units and "long-seat" trainsets, but both are formed of ten coaches and can be used for through-services towards the Tokyo Metro Fukutoshin, Yurakucho, Tokyu Toyoko and Minatomirai Lines.
The "dual-seat" trainsets are used on both the Seibu Shinjuku and Ikebukuro Lines. They have convertible seating (longitudinal to transverse seating and vice versa), accessible toilets and power outlets for passengers. It is not well known that the outlets can be used even when seats are set to longitudinal-position. Seats are set to transverse-position when used on S-Train or Haijima Liner (Seibu-Shinjuku - Haijima), but they are not as comfortable as other limited express services on the Seibu network (001 series and 10000 series).
The "long-seat" trainsets are allocated to the Ikebukuro Line, and mainly used on through-services to Tokyo Metro and even towards Yokohama as mentioned above, along with 6000 series.
Current Operations & Future Prospects
Six "dual-seat" trainsets are mainly used for S-Train and Haijima Liner, with a few on other services in accordance with fixed timetables. S-Train at weekend (Seibu-Chichibu - Motomachi Chukagai via the Tokyo Metro Fukutoshin, Tokyu Toyoko and Minatomirai Lines) is disproportionately expensive in spite of journey times and comfortability, attracting far fewer passengers than initially anticipated.
Other "long-seat" trainsets are used for ordinary services on the Ikebukuro Line and the through-services, as well as the Shinjuku Line. They do not require any additional ticket.
The company will introduce another variant of the series called Tokiiro to the Shinjuku Line, which enters into service in spring 2027 and replaces the 10000 series. The Tokiiro trainsets will be formed of eight coaches with convertible seating.