The headway in Korean national railway normally runs from 6 to 10 minutes. It turns out that the current signal system can not decrease the running headway of the High Speed trains, which are scheduled to set out in April, 2004, between Seoul and Daejeon, since both the existing classical trains and the High Speed ones run on the section. Thus, a new signal system is to be introduced to secure safe and reduced headway. The present paper attempts to analyze the headway between this particular section Seoul-Daejeon of the classical line, where we expect the most severe bottleneck situation to occur. We employed two modes in our analysis : the Ground Signal mode and the On-board Signal mode. which are to be adopted starting from 2006.