This research estimated decreased vibration level as quantitative according to change of track system on Seoul Subway Line No. 1 from existing ballasted track system(Pandrol type clip) to concrete track system(Youbgdan type isolation rubber clip). Following change to concrete system, vibration level at tunnel floor decreased between 4-8dB(V). Vibration equations suggested in this paper consider the velocity of train and can estimate quantitative vibration response. These are divided by ultimate limit state($eta$=0), serviceability limit state($eta$=1.28) and safety state($eta$=3), respectively. The reliability index, $eta$=0, means 50％ data line obtained by least squares best-fit line. The reliability index $eta$=1.28 and 3 represent boundaries below 90％ and 99.9％ respectively.