In order to realize low-cost track maintenance for regional railway lines, the authors successfully developed the track management system based on the car body vibration data, which are measured on commercial passenger trains by a smartphone with MEMS and GPS velocity meter. After the compensations using numerical filtering of GPS velocity and the waveform-matching between the “car body vibration fluctuation” and the “track longitudinal level irregularity change”, the reproducibility and the accuracy of track position are increased and the measured data become reliable enough for track maintenance. According to the analysis on collected huge data for more than 3 years, the relationship of the train vertical vibration vs. the track longitudinal level irregularity has good positive correlation, so, the track condition can be expected from daily train vibration monitoring. As a result of these studies, the authors propose a new economic track management approach.