In Situ Assessment of Track Geometry Degradation and Defect Scoring for Maintenance Prioritization: A Case Study on a Railway Section Line M300, Romania

Railway track geometry degradation is a key determinant of infrastructure safety, ride comfort, maintenance demand, and lifecycle cost. This paper presents a measurement-based assessment of track geometry degradation on the analyzed section of railway line M300 in Romania, with emphasis on its practical use for maintenance prioritization. The study uses in situ track-geometry inspection records collected by a track-measuring vehicle (VMC) between 2020 and 2023 on a curved double-track sector, and evaluates the main geometric defect families used in railway practice, including alignment, gauge, longitudinal level, cross-level, and twist. In addition to conventional defect identification, severity grading, and penalty-point scoring, the paper uses a maintenance-oriented interpretation framework based on the campaign-level Defect Severity Index (DSI), the Defect Recurrence Factor (DRF), and the Maintenance Priority Matrix (MPM). In this framework, DSI corresponds to the normalized penalty score per kilometre and is used to compare inspection campaigns, while DRF and MPM extend the interpretation by identifying persistent defect families and translating measured degradation into maintenance priorities. The results show that degradation is non-uniform over time and defect-family-dependent, with cross-level and longitudinal-level defects dominating the cumulative penalty score. The DSI ranged from 467 points/km in September 2022 to 3183 points/km in March 2022, confirming a non-linear degradation and recovery pattern. The proposed indices provide an interpretable extension of the existing penalty-point framework and support condition-based maintenance planning on conventional railway lines.