The 4000 series trains are the first in the world to implement synchronous reluctance motors on a full scale; they are expected to offer 20% energy savings over older, induction motor-driven trains.

[1] The trains use bogies with steerable axles to reduce noise on curves.

[4] It was announced on 7 February 2022 by Kawasaki Heavy Industries that its rolling stock division, Kawasaki Railcar Manufacturing, would produce the new trains at a cost of approximately ¥10 billion (2022) (US$76.05 million).

[5] Details of the trains were first announced by the Fukuoka City Transportation Bureau on 30 November 2023.

[6][1] The first set, 25, was delivered from the Kawasaki Railcar Manufacturing plant in Hyogo from 23 April 2024.