The Gimpo Goldline - an automated, unmanned metro service opened in 2019 - has become unable to handle demand, leading to dangerous overcrowding in train stations. The new train line connects Gimpo, west of Seoul in Gyeonggi Province, to the capital s subway system via Gimpo International Airport Station. Its two-carriage trains have been derided as a “mini-subway.” But the trains can t be extended, because the subway platforms were only built for two carriages.