and signboards, the line is shown using the color red (). Its stations are given numbers using the prefix "M"; Hōnanchō branch line stations carry the prefix "Mb", which replaced the previously used lowercase "m" prefix in November 2016. Station list All stations are located in Tokyo. Some trains leave the main line at Nakano-sakaue (M-06) for the Marunouchi Branch Line to Hōnanchō. Main Line Branch Line (Honancho Line) Rolling stock Marunouchi Line services are operated using a fleet of 53 Tokyo Metro 02 series six-car EMUs in service since 1988 together with six three-car sets used on Hōnanchō branch services. All trains are based at Koishikawa and Nakano Depots. A fleet of 53 new Tokyo Metro 2000 series six-car trains was scheduled to be introduced from fiscal 2018, replacing the 02 series trains by fiscal 2022. On February 23, 2019, the 2000 series started operation. Former TRTA 500 series/TRTA 300/TRTA 400 series/TRTA 500 series/TRTA 900 series (from 1954 until 1996, later sold and exported for use on Line B of the Buenos Aires Underground) TRTA 100 series (from 1962 until 1968, transferred from Ginza Line, used for Hōnanchō branch only) TRTA 2000 series (from 1968 until 1981, used for Hōnanchō branch only) History The Marunouchi Line is the second subway line to be built in the city, and the first to be constructed after the Second World War. Its design is similar to that of the Ginza Line, the oldest subway line in Tokyo. Both lines are standard gauge and use third rail power, unlike subsequent Tokyo subway lines which use overhead wires and are mostly narrow gauge to accommodate through services with other railway lines. In a 1925 plan for a five-line subway system, the Marunouchi Line was planned to run from Shinjuku to Ōtsuka via Hibiya, Tsukiji and Okachimachi, as a underground route. A segment between Akasaka-mitsuke and Yotsuya began construction in 1942, but was abandoned in 1944 as a result of the continuing effects of World War II. On December 7, 1946, the Marunouchi Line was revised to begin from Nakano-fujimichō to the Mukōhara neighbourhood in Toshima Ward via Kanda and Ikebukuro, for a total length of . On March 30, 1951, a groundbreaking ceremony was held at Ikebukuro Station East Exit to begin construction of the initial segment of the Marunouchi Line. The first section was opened between Ikebukuro and Ochanomizu on January 20, 1954.