Heian Azuma Line

The Heian Azuma Line (平安東線) is a high-capacity line in Heian operated by the Heian Mass Rapid Transit Corporation. It runs in a loop connecting the eastern part of the metropolis, with its official start and end point being Heian Azuma Station. The Heian Azuma Line is automated and driverless, and is amongst the world's longest driverless train lines. Its colour is orange.

The Heian Azuma Line was conceived in the 1980s in an attempt to ease street congestion and reduce passenger load on the aboveground Kyobashi Line. Planning began in 1985 by the Heian Metropolitan Government as well as the Heian Mass Rapid Transit Corporation. Construction officially began in 1989, utilising tunnel-boring machines to avoid disrupting surface traffic to a major extent. The line first opened in 1995 with five stations completed, connecting Kishiwada with Shitamachi and extending to Kawatsui, where the depot is located. The rest of the line was opened progressively over six phases, with the loop fully completed in 2013. The line began trasitioning to fully automated driverless trains in 2009, introducing the Kawazaki Heavy Industries Type-09 trainsets and phasing out the manned Type-98 Kai 2 trainsets that the line had been using.