Evaluating the Equivalency Between Track Quality Indices and the Minimum Track Geometry Threshold Exceedances Along a Canadian Freight Railway

Railway regulators require that track geometry measurements meet a specific set of minimum safety thresholds. A proper interpretation of track geometry survey data is fundamental for the detection of track exceeding these thresholds and in need of corrective maintenance. Irregular track geometry independent of the minimum safety thresholds can also be used as evidence of degradation in the railway foundation. Therefore, multiple evaluation methods must be applied to the track geometry survey data when assessing foundation degradation. In this study, we compare multiple track geometry evaluation methods in order to assess if they equally identify sections of irregular track geometry along a 335 kilometer section of a Canadian freight railway. The track geometry evaluation methods investigated are the Transport Canada Class 5 minimum safety threshold exceedances and three literature-suggested track quality indices; the Overall Track Geometry Index, the Polish J Index and the Swedish Q Index. Furthermore, this study also investigates the ability of the track quality indices to provide additional insight into track geometry variability in sections without a minimum safety threshold exceedance. The track under investigation is not a Class 5, however, Class 5 minimum safety thresholds were used to produce enough threshold exceedances to allow for the comparison to the track quality indices. The results of the analysis reveal that while the large-scale variability in the three track quality indices is similar, the individual equivalency with the occurrence of Class 5 threshold exceedances is highly variable. Furthermore, only the Overall Track Geometry Index demonstrates the potential to provide consistent additional track geometry variability information.