Undergrounds and other metropolitan railway systems are characterized by their intense traffic, lasting up to 20 h per day, and so they need their maintenance work programmes to be optimized, implying an optimization of the monitoring processes. This article proposes an alternative to the traditional optical methods for monitoring rail profiles which can only be carried out by special vehicles. This is a new procedure that obtains the rail profile by means of inertial methods. The model this work is based on takes its input from the vertical accelerations produced in railway axles measured in trains running on regular services and calculates the rail irregularities that have originated them. The model uses the Fourier transform in order to solve the equations and find the transfer function that relates the input function and the output function in the frequency domain. The solution is then reverted into the time domain by applying the inverse Fourier transform. Data input comes from real measurements taken on line 9 of the Madrid underground, and the model's effectiveness was then analysed by comparing the output data with the rail profile taken using optical methods.

This paper uses the finite element method to analyse the mechanical behaviour of different track types by considering the different conditions to which they may be subjected: superstructure, height, embankment and foundation quality. The values of the stress and deformation as a function of depth are obtained at each point of the cross-section of the considered track. These values allow quantification of the basic design parameters for railway structures: track stiffness and stress supported by the railway platform. Optimal combinations of superstructure, height, embankment and foundation materials are presented for various specific operation conditions. The presented information can be used to improve the design of railway structures.

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