Design and maintenance of high-speed rail tracks: A comparison between ballasted and ballast-less solutions based on life cycle cost analysis

摘要

The increase of train speed and axle load in the European rail network is an essential goal to make the railway transport more and more competitive for passengers and freights. High speed trains call for a better structural and geometrical stability of the track. To this aim it is crucial to apply innovative track design and materials. In the last decades, various types of ballast-less track systems have been developed and put in service around the world. These systems seem to perform better than ballasted solutions especially when high-speed passenger trains share the track with freight trains. The main advantages of innovative slab systems are the following: low maintenance needs/costs, higher availability, increased service life (50-60 years), higher lateral stability, reduction of weight and height of the track, easier and more economic vegetation control. Weaknesses of slab tracks against ballasted tracks are as follows: higher construction cost, higher noise radiation. In the light of the above considerations, in the study presented in this paper a life cycle cost assessment of two competing track solutions (ballasted and ballast-less) has been carried out, considering short- and long-term perspectives. Cost analysis uses the present value of agency (construction, inspection, maintenance and renewal), environmental (CO_2 emission), and user (delays-related etc.) costs. The analysis of the trend of agency, user, and externality costs of the alternatives over the entire life cycle of the infrastructure allows recognizing the most sustainable option. Results show that solutions that are more affordable in the short term can yield maintenance and renewal processes which are unfavorable or less sustainable in the long term. Furthermore, in the long term, the difference between the (total) present values of the two solutions becomes too small to yield sound conclusions in favor of the ballast-less solution with respect to the ballasted one.