ABSTRACT: The longitudinal variation of support stiffness is believed to be a key driver for the differential settlement of the ballast. This paper presents an innovative approach to correlate these two variables. In order to overcome the lack of input data, a statistical model is applied and the spatial correlation of the input stiffness data is controlled to generate naturally occurring variations. A large set of simulations is run and the relationship between deterioration rate and support properties is then analysed using log-linear multiple regression models. The results show that it is not only its mean value that has an impact in the long term settlement behaviour, but it is also its longitudinal variability. Also, main results suggest that the speed effect might be more crucial in localized corrective maintenance needs than in preventive maintenance needs.