The Korean Railway Workers’ Union said Wednesday it would launch an indefinite strike on Dec. 10 unless its demands for more safety staff and a fairer promotion system are met. The walkout could affect high-speed trains serving Seoul’s Suseo Station as well as other Korail services. In previous Korail strikes, SRT trains continued to run under a separate operator, giving passengers an alternative. Korail took over SR’s high-speed rail operations on Sept. 1, and trains formerly marketed as SRT no