## 3 Trackside Measurement through Field Instrumentation
### Field Measurement Result Comparison
These factors can serve to indicate that certain track types may be more subject to performance change due to increasing speed of the trains than others. For easier comparison purposes, the peak values for the respective track structures/types of the two classes of tracks were derived among the 5 different speed conditions (from 120 to 170 km/h). With the exception of the track support stiffness, as there is no standard criteria for maximum track support stiffness in the KR-C 14030 railway track performance evaluation criteria, the evaluation parameters for wheel load fluctuation, derailment coefficient and stress were compared to the maximum limits outlined in the specification code. The results are shown in Table 11 for ballasted track structures and in Table 12 for concrete track types. As can be seen in the results, the two classes of track structures show high variance between one another, but amongst the structure and types, the differences are low, but not completely negligible. For instance, Type 1 and Type 2 ballasted track structures are up to 57-66 percent of the maximum allowed wheel load fluctuation rate. Based on the limited information given, one could surmise that the cause of this difference is due to the higher overall stiffness at the rail and wheel contact point, supported by the spring constant of the substructure of the track, but again with only the evaluation results, it is difficult to understand the precise reason. The derailment coefficient was similar between all types and classes of tracks, where the range was between 14-20% of the maximum allowed coefficient, and this was the same with the case of the stress parameter, ranging between 17-33% of the maximum allowed stress limit. The conventional state of the track performance assessment regime does not perform additional analysis or inquiry into the difference in the figures of these evaluation results (unless the analysis results pass the maximum limit), and additional clauses or instructions are not found in the KR-C 14030 or other design code specifications or standards. The difference in the evaluation result values, particularly between the ballasted and concrete track structures, is no coincidence. The reasons for the differences can be estimated as was attempted in some of the sections in the above, but it is clear that there is currently a strong limitation in the adopted design code and the evaluation criteria. The results of this study lead to proposing that further investigation of the correlation between the track structure properties and track performance is required, and that current evaluation methods and criteria found in the adopted national standards and design codes undermine the importance of this factor. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Track** & **Wheel Load Fluctuation** & **Deralment Coefficient** & **TSS (Peak TSS)** & **Stress (Max** \\
**Structures** & **(Max: 0.8) (\%)** & **(Max: 1.2) (\%)** & **(kN/mm)** & **200 MPa) (\%)** \\ \hline Type 1 & 57 & 19 & 142.88 & 28 \\ Type 2 & 66 & 19 & 174.46 & 32 \\ Type 3 & 36 & 14 & 140.96 & 30 \\ Type 4 & 15 & 18 & 113.35 & 33 \\ Type 5 & 24 & 18 & 166.07 & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Evaluation results of track performance (ballasted track structures). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Track** & **Wheel Load Fluctuation** & **Deralment Coefficient** & **TSS (Peak TSS)** & **Stress (Max** \\
**Structures** & **(Max: 0.8) (\%)** & **(Max: 1.2) (\%)** & **(kN/mm)** & **200 MPa) (\%)** \\ \hline Type 1 & 6 & 14 & 66.35 & 24 \\ Type 2 & 7 & 20 & 74.71 & 20 \\ Type 3 & 10 & 22 & 95.13 & 23 \\ Type 4 & 7 & 18 & 98.69 & 17 \\ Type 5 & 8 & 17 & 93.45 & 21 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Evaluation result of track performance (concrete track types).