Influence of ballast and railway substructure on the degradation of local geometry defects

The degradation of track geometry is a very complex phenomenon that has typically been analysed considering global quality indicators. In this paper, the influence of ballast and track substructure on its geometric degradation is analysed by modelling the degradation rates of more than 17,400 local defects of longitudinal levelling, alignment, and twist from 66,892 km of track inspection measurements carried out during the period 2001-2012 on 19 conventional lines of the Portuguese railway network. It is corroborated that singularities markedly contribute to greater density and faster degradation of defects, especially culverts and level crossings. Ballast type and age significantly affect the probability of emergence and degradation rates of defects. In a significant number of situations, defects are found to degrade much faster than the standard deviation indicators, highlighting the importance of monitoring and modelling their evolution to prevent the need for carrying out corrective interventions as much as possible.