Three days have passed since Korail workers went on an indefinite strike on Wednesday.
Train operations have fallen to 82 percent of the usual rate, causing delays on subway lines one, three and four.
Interval times for Gyeongui Jungang Line also increased to more than 30 minutes,10 to 20 minutes longer than usual, affecting residents in Gyeonggi-do Province.
During commuting hours, Korail plans to put more workers in place to maintain train levels at 90 percent.
High-speed KTX trains will operate at around 70 percent and other trains at 60 percent of their usual services.
The Korean Railway Workers' Union said roughly half of its workers are participating in the strike.