Railway tracks, Track surface diagnostics, Track geometry

In the diagnostics of railway track geometry, one of the more complex problems is determining the limit values for measured track irregularities and defining the impact of their simultaneous occurrence on a single micro-section of the track on ride safety. In practice, this leads to many misunderstandings, especially during the investigation of railway accidents, where a single exceedance of a permissible deviation is very often interpreted as the cause. The article discusses the issue of the coincidence of railway track geometric irregularities at low train speeds. Particular attention is paid to the simultaneous occurrence of track twist, cant, and horizontal irregularities on a short section of the track.In practice, geometric diagnostics of a railway track boils down to measuring four basic parameters: vertical and horizontal irregularities, the difference in rail height (cant), and track gauge, followed by calculating the gauge gradient and track twist. In the next stage, the measured values are compared with permissible values, which have been determined based on the ride comfort criterion.
In the event of exceeding the permissible values, appropriate maintenance decisions must be made, e.g., performing repairs or restricting train speed.
Such an approach very often leads to erroneous maintenance decisions or misunderstandings when determining the cause of a rail vehicle derailment. It happens that, on one hand, the exceedance of a single permissible deviation is associated with the direct cause of an accident, while on the other hand, large values of several measured irregularities on a single micro-segment of the track are treated separately, ignoring their simultaneous occurrence. (…)

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