Busan, Seoul, Pyeongtaek (Camp Humphreys), and Daegu (Camp Henry and Walker) have extensive subway systems that connect to the KTX (Korea Train Express) trains. Chinhae relies on a bus and taxi system.
There are several metro apps for smart phones available that provide maps and routing assistance.
Most locals purchase metro cards from convenience stores that can be recharged and used in metros throughout the country. Paper tickets may be bought from kiosks, if preferred.