The first day of a “work-to-rule” protest by the Korean Railway Workers’ Union resulted in only minor subway delays in the Seoul metropolitan area as the union continues to demand the hiring of additional personnel.

According to the Korea Railroad Corporation on Monday, 140 out of 650 commuter trains during the morning rush hour saw delays of more than ten minutes, while 120 trains were delayed by over 20 minutes.

Seoul subway lines 1, 3 and 4 were affected, as well as the Suin-Bundang, Gyeongui-Jungang and Seohae lines.

But the high-speed KTX and other regular trains are operating on schedule.

The union is demanding a transition to a four-team, two-shift work system, with additional personnel and a two-point-five percent increase in the base salary.