# Development and Operation of Track Condition Monitoring System Using In-Service Train
## 3 Track Condition Monitoring Results Using Vertical Vibration Acceleration
### Track Condition Diagram  
Figure 4 shows the track condition diagram for Section CD. The horizontal axis in Figure 4 represents the distance, and the upper row shows the track condition diagram created based on the aforementioned single-sided maximum amplitude value. The vertical axis represents the measurement date; here, the date of the first measurement of each month is displayed as a reference value. At different times of day, the data with the highest one-sided maximum amplitude value are displayed as representative data.  
The lower section of Figure 4 is a histogram showing the frequency of threshold exceedance, where the number of times the one-sided maximum amplitude value of each datum exceeds the threshold of 1.0 [m/s\({}^{2}\)] is normalised by the number of times the train operates. This enables the deterioration degree and track position to be estimated.  
For cases in which multiple test trials were conducted in one day, the highest measured values of the one-sided maximum amplitude for the trials are shown herein as representative values. In the lower section of the diagram, the number of times the single-sided maximum amplitude of each test datum exceeded the threshold of 1.0 [m/s\({}^{2}\)] is normalised by the (total) number of test trials, and the histogram of the frequency of threshold exceedance is shown. The average velocity for all test data, as indicated by a red line, is used as a reference.  
Figure 3: Locations where high accelerations were observed in a regional railway. It is pointed out that if the vertical acceleration exceeds 2.8 [m/s\({}^{2}\)] in the driver’s cab, track maintenance should be carried out as soon as possible [34]. For this reason, this figure defines an acceleration of 3 [m/s\({}^{2}\)] or more as a significant car-body vertical acceleration.  
As shown in Figure 4, high vibration accelerations occurred frequently in the sections from 1.1 to 1.2 km and from 1.4 to 1.5 km. Next, we investigated whether longitudinal-level irregularities occurred in these sections. Tables 1 and 2 show the locations where the measurements exceeded the target value of track irregularity correction for riding comfort and the corresponding level of irregularity, as indicated by the track geometry measurement results for the sections from 1.1 to 1.2 km and from 1.4 to 1.5 km. The inspections were conducted in September 2020.  
As shown in Tables 1 and 2, track irregularity, which indicates track degradation, occurred continuously in both sections. Accordingly, sections with degraded tracks can be identified. In the next subsection, we discuss the changes in vibration acceleration over time in these sections.  
The data presented in this paper include the effect of this train speed change. The authors also propose a more accurate evaluation method that does not depend on the effect of train speed [21]. The sections evaluated in this paper have not been corrected for the effect of train speed, as the speed changes were small (AVE: 35.0 km/h, SD: 5.3 km/h at 1.15 km, AVE: 30.5 km/h, SD: 4.7 km/h at 1.45 km). Additionally, if the in-service train to be measured changes, the data to be measured will also change. For this reason, measurements are always taken on the same train.  
Figure 4: Track condition diagram of vertical acceleration for Section CD. Averaged speed profile for all runs is shown at the middle of the diagram. AVE: 35.0 km/h, SD: 5.3 km/h at 1.15 km, AVE: 30.5 km/h, SD: 4.7 km/h at 1.45 km. Speed profile for all runs is shown at the bottom of the diagram.