The Toei Asakusa Line, operated by the Tokyo Metropolitan Bureau of Transportation, sits at the centre of one of Tokyo's most extensive through-running networks. When its first section opened on 4 December 1960 it simultaneously began through-running with Keisei Electric Railway, making it the first subway line in Japan to offer through services with a suburban private railway.
The network expanded southward on 21 June 1968 when the line reached Sengakuji and through-running with Keikyū Corporation began, connecting the chain toward Kanagawa Prefecture and ultimately to Haneda Airport via the Keikyu Airport Line. Hokuso Railway joined on 31 March 1991, extending trains into Chiba, and Shibayama Railway was added on 27 October 2002. The opening of the Keisei Narita Sky Access Line on 17 July 2010 added a route to Narita Airport via the Hokuso Line. With its Keikyu and Keisei through services, the Asakusa Line network is the only one offering direct connections between Tokyo's two main international airports, Haneda and Narita.
Service pattern
Most trains run through onto other operators' lines, and a single train runs over the tracks of up to four operators. Trains serving both airport access corridors — the Keikyu Airport Line toward Haneda and the Keisei Narita Sky Access Line via Hokuso toward Narita — share the core Toei Asakusa Line trunk between Sengakuji and Oshiage.
Timeline
1960On 4 December 1960 the Toei Asakusa Line opened its first section (Oshiage–Asakusabashi) and simultaneously began through-running with Keisei Electric Railway — the first time in Japan that a subway line offered through services with a suburban private railway.
1968On 21 June 1968 the line extended from Daimon to Sengakuji, and through-running with Keikyū Corporation began, connecting the network southward toward Kanagawa.
1991On 31 March 1991 through-running with Hokuso Development Railway (now Hokuso Railway) began, extending the network's reach in north-western Chiba.
2002On 27 October 2002 Shibayama Railway joined the network, adding the terminal Shibayama-Chiyoda station.
2010On 17 July 2010 the Keisei Narita Sky Access Line opened, adding a route to Narita Airport via the Hokuso Line corridor.
