Fractal analysis as an innovative approach for evaluating the condition of railway tracks

Abstract

The deterioration of ballast and the consequences of weak subsoil increase the need for track maintenance. These problems reduce the service life of tracks, and a higher maintenance budget is required. This paper introduces an innovative method for evaluating the condition of the ballast and the subsoil. Fractal analysis of the vertical track geometry enables infrastructure managers to determine the root cause of track irregularities by quantifying the wavelength characteristics of the common track geometry data. This methodology determines whether the ballast or the substructure condition is the cause of poor track quality. Fractal analysis has been carried out to date on the main network of the Austrian Federal Railways, which comprises some 4000 km of track, as well as within the network of Suisse Federal Railways (∼5000 km). Additionally, several lines in the United States (Amtrak), Belgium (InfraBel), and Denmark (BaneDanmark) have been evaluated. A detailed validation process has been carried out to investigate different characteristics and their correlation to the in situ behavior of the track. This research is now showing promising results after being cross-checked with historical data and compared to the implemented maintenance measures. On-site inspections have confirmed the evaluated component-specific condition.