Study of loaded versus unloaded measurements in railway track inspection

To keep railway operations safe, track geometry parameters such as track gauge are usually inspected using track geometry cars. The measurement frequency of track geometry cars is low at twice per year due to high operational costs and limited access to networks. Mobile track inspection systems such as Fugro’s RILA technology are an innovative way to inspect tracks frequently and affordably, since they can be easily mounted on passenger or freight trains. Besides track geometry, RILA also creates a digital copy of railway corridors, providing asset managers with the ability to make fully informed decisions on track assets. However, the data collection sensors on mobile systems are further away from the axle than track geometry cars, and they provide unloaded and loaded measurements respectively. This difference may lead to a discrepancy in measurement results.

This paper studies the difference between loaded and unloaded measurements, using experimental and numerical methods. In the experimental research, a section of track was measured using both systems. When the results were compared, a discrepancy was reported; although the measuring distance can cause discrepancies, the unloaded measurement method still meets the measurement requirement. The largest discrepancies are in track transition zones, which is explained using the numerical method. After that, a case study on the unloaded measurement method, using Geo-data collected by Fugro’s RILA technology, is presented, wherein a section of track was measured every month. The results demonstrate the advantages of frequent measurements during track inspections and the potential applications of unloaded track inspections.