The 7.4km extension is almost entirely underground, and has historical significance as it will re-establish a rail connection between Songdo and Incheon - the original narrow-gauge line closed in 1973.


The new extension has five intermediate stations and will provide easier access to one of the city's international ferry terminals, and various industrial and residential areas.

The original section of the Suin Line opened in 2012 between Songdo and Oido where it connects with Line 4 of the Seoul metro. Eventually the Suin Line will be extended from Oido to Suwon to connect with the Bundang Line.