This paper analyzes rail-track geometry degradation and uncertainty related to the phenomenon on the basis of the inspection of car records from recently upgraded sections of the Lisbon-Oporto line. Statistical analysis is performed distinguishing four groups of track sections based on the features of the infrastructure. For each group of track sections, lognormal distributions are fitted to track geometry degradation parameters. Moreover, important correlations between degradation parameters are explored, so that the assessment of the maintenance cycles of future upgraded lines can integrate them through simulation. Spatial linear correlations between degradation parameters are also explored, and some that may influence life-cycle maintenance, renewal, and unavailability costs are highlighted.