Seibu 40000 series

Data (as of 1 Sep 2026)

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 three groups in service: "dual-seat" units consisting of ten coaches, "long-seat" trainsets formed of ten coaches, and that of eight coaches.

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 for 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 ten-carriage units are mainly used for through-services to Tokyo Metro and even towards Yokohama as mentioned above, along with 6000 series. Eight-carriage units are used only on the Seibu Ikebukuro Line.

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. They do not require any additional ticket. Sometimes a few units run the Seibu Shinjuku Line as well.

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.