Interface - The Journal of Wheel/Rail Interaction

PERFORMANCE-BASED ASSESSMENT

Using Performance-Based Assessment of Reserve Gauge Strength to Enhance Tie-Replacement Planning (continued)

A walking inspection was performed on the entire length of the tangent section at Site 11, between MP 138.3 and 138.6 (see Figure 5b). As Figure 5b indicates, there was good agreement on tie counts between the visual inspection and the performance-based assessment. The Figure shows that there was a lot of weak track in this tangent segment. The 3-degree curve beginning at 138.6 is clearly stronger than the preceding tangent and 1-degree curve, indicating that the 3-degree curve had undergone maintenance prior to the inspection.

The 3-degree curve at site 12 was also chosen for further inspection because there were significantly different tie counts produced by the two methods (see Figure 5c). A walking inspection was performed on the entire curve, about 3/4 miles in length. The chief tie inspector agreed that the GRMS, performance-based tie count at 375 ties was much closer to what was actually required than the 89 ties counted by the standard, visual method. It was not clear why the visual tie count in this curve was so low.

What can we infer from the field inspection of 15 sites within 57 miles?

One conclusion is that there is still far too much subjective variability in the tie counts by trained walking inspectors. Reducing this variability is key to improving tie renewal programs and effective use of the budget. Another conclusion is that the performance-based track-strength assessment provided by GRMS, at the very least, provides quantitative data that can be used to correlate and improve the information derived from visual inspection. Clearly, there are weak tie conditions that are not effectively found by inspectors who are walking 5 miles of track or more per day.

Additionally, there is good evidence that performance-based assessment generally selected fewer ties in tangents and more ties in curves. This is contrary to the general tendency of walking inspectors, who tend to select more ties in curved track than in tangent.

Performance-based strength assessment can enhance and improve the tie-replacement decision process, and has the potential to improve safety and optimize the value received from available tie budgets. Of course, visual inspection is still required to identify tie conditions that are not strictly related to gauge strength, but still call for replacement. Nonetheless, performance-based assessment provides the potential to compare or prioritize subdivisions or track segments for program work.

In the future, the combination of performance-based track strength assessment coupled with developing “automated visual inspection” or “machine vision” technologies may hold the key to eliminating the subjective walking inspections that have been in place, more or less, since the dawn of railroading.

Robert Madderom is Vice President and General Manager of the Holland LP’s Railway Measurement Systems & Services Division.

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