[6] The western part of Adachi is poorly served by public transport and planning of the line started in 1985, with the initial intention of constructing a full-fledged subway.

However, this was scrapped due to the high cost and projected low ridership, and a more cost-efficient AGT system was selected instead.

[7] The main contractor was the Tokyo Metropolitan Subway Construction Company, which also built the Toei Oedo Line.

[citation needed] A 5.9 magnitude earthquake[8] partly derailed three cars of a train of the Nippori-Toneri Liner at 10:41 pm on Thursday, 7 October 2021.

^ Crowding levels defined by the Ministry of Land, Infrastructure, Transport and Tourism:[10][11]