E231 series

The E231 series (E231系) is an electric multiple unit (EMU) train type used for commuter and outer-suburban services operated by East Japan Railway Company (JR East) in Japan since 2000.

Design

Trains were manufactured by Tokyu Car Corporation, Kawasaki Heavy Industries and also at JR East's factory at Niitsu in Niigata Prefecture.

Variants

The type evolved from the earlier 209 series and E217 series EMUs, with the main visible difference being wider bodies (2,950 mm compared to the 2,800 mm for earlier commuter trains), and the prototype train built in 1998 for trials on the Chūō-Sōbu Line was actually classified 209-950 series, later becoming E231-900 series. Full-production E231-0 series trains were subsequently introduced on the Chūō-Sōbu Line (10-car sets) and Jōban Line (10+5-car sets). Other variants include the 11-car E231-500 series for the Yamanote Line, and the E231-800 series with 2,800 mm wide bodies and end doors for use on Tokyo Metro Tōzai Line interrunning services.