Multi-criteria analysis applied to railway rehabilitation

The railway infrastructure has very specific constraints that lead to the need of maximizing of the availability of infrastructure, with high levels of safety and quality, associated with an optimized cost. Having said this, it is essential to understand the methods behind the inspection and monitoring of existing railway infrastructures, the way of processing their data, as well as existing rehabilitation solutions. The present work begins with a brief description of the components of the ballast track and its operation, the different types of actions to which it is subjected to and the degradation mechanisms at the level of the ballast layer, substructure and transition zones, with particular attention being given to the latter since it is a section of the road with singularities that lead to a more pronounced degradation. The rehabilitation solutions addressed in this work start from a slight attack of the road (which can be considered as a small intervention) until a complete renovation of the road with reinforcement of the foundation. Based on the previously mentioned concepts, it is possible to define which variables, criteria and respective weights are more important and influence the investment decision (on the rehabilitation of the railway infrastructure), thus enabling the methodologies of multi-criteria analysis applied to these variables. Currently, the economic factor is one of the variables that influence the most in decision making due to the lack of investment capacity. Mainly because of this factor and sometimes even without performing an analysis, one of the common practices is the restriction of circulation velocity rather than maintenance or rehabilitation measures. The case study used is an excerpt from a railroad in Portugal, where the entire described process will be applied and consequently analysed. Therefore, this work intends to contribute to a more efficient planning of the railway maintenance and rehabilitation measures, based on a better use of the data resulting from the track inspection, through a multi-criteria analysis.