# Evaluation of Measurement Strategy for Track Side Monitoring of Railway Wheels
## 4 Results and Discussion
The highest mean value for flange width (Sd) was found to be associated with wheel HP6448, and the largest standard deviation for the estimated flange width was found to be for wheel HP9270. The highest range (0.580 mm) for the flange width was observed for wheel HP7480. The average standard deviation for flange width for the measurements across all the wheels in the study was 0.1 mm around their mean value with an average range of 0.48 mm. The highest mean value for flange slope (qR) and the largest standard deviation of the same was associated with wheel HP6448. The range for estimated flange slope was largest for wheel HP9709 with a value of 0.38 mm. The average standard deviation and average range of the estimated flange slope across all the wheels were 0.067 mm and 0.27 mm, respectively. The hollow wear or the tread hollow (Th) was zero for three of the wheels studied (two wheels being new). The highest mean value, standard deviation, and range for hollow wear/tread hollow (Th) were observed for wheel HP9709, which had the highest running distance among all the wheels observed in this study. The average standard deviation and average range of hollow wear across all the wheels that exhibited hollow wear were observed to be 0.08 mm and 0.4325 mm, respectively. These statistics indicate that there are variations in the estimated wheel parameters for different measurement positions within the same wheel. Figure 6 depicts a histogram plot of flange height measured for eight different wheels. The highest average mean flange height value was associated with wheel 1 (measured 8 times). The largest standard deviation around the mean value (0.517 mm) and the largest range (1.44 mm) for the flange height was found to be for wheel 2. The average standard deviation across all the wheels for the estimated flange height was 0.422 mm, and the average range was 1.07 mm. The average standard deviation of flange height estimated using the wayside measurements was over four times higher than when using the handheld equipment, and the average range was over two times. Figure 7 depicts the histogram plot of the flange width measured for eight different wheels. The highest mean value for the flange width was observed for wheel 2 with a value of 29.88 mm. The largest standard deviation around the mean value (1.028 mm) and the largest range (3.33 mm) for the estimated flange width was found to be for wheel 1. From the histogram plot, the spread in the flange width values is quite significant. The average standard deviation across all the wheels for the estimated flange width was 0.815 mm, and the average range was 2.5 mm. The average standard deviation of flange width estimated using the wayside measurements was over eight times higher than when using the handheld equipment, and the average range was over five times. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c} \hline \hline
**Wheel** & \multicolumn{4}{c}{**Mean (mm)**} & \multicolumn{4}{c}{**Standard Deviation (mm)**} & \multicolumn{4}{c}{**Range (mm)**} \\ \cline{2-13}
**Id** & **Sh** & **Sd** & **qR** & **Th** & **Sh** & **Sd** & **qR** & **Th** & **Sh** & **Sd** & **qR** & **Th** \\ \hline HP8628 & 28.283 & 27.486 & 9.564 & 0 & 0.114 & 0.091 & 0.059 & 0 & 0.440 & 0.330 & 0.280 & 0 \\ HP9270 & 28.267 & 29.142 & 9.783 & 0 & 0.086 & 0.131 & 0.0628 & 0 & 0.350 & 0.500 & 0.270 & 0 \\ HP8507 & 32.757 & 26.013 & 9.934 & 0.450 & 0.085 & 0.110 & 0.041 & 0.067 & 0.340 & 0.550 & 0.180 & 0.350 \\ HP7480 & 35.243 & 26.352 & 11.267 & 1.144 & 0.088 & 0.057 & 0.063 & 0.043 & 0.440 & 0.580 & 0.300 & 0.400 \\ HP6448 & 33.867 & 30.052 & 12.479 & 0 & 0.094 & 0.093 & 0.104 & 0 & 0.390 & 0.400 & 0.360 & 0 \\ HP9264 & 34.141 & 28.684 & 11.033 & 0.118 & 0.100 & 0.099 & 0.044 & 0.102 & 0.420 & 0.490 & 0.160 & 0.390 \\ HP9709 & 36.138 & 26.893 & 12.065 & 2.148 & 0.121 & 0.121 & 0.092 & 0.105 & 0.510 & 0.530 & 0.380 & 0.590 \\ \hline \hline \end{tabular}
\end{table}