Carrying capacity of railway networks: interaction of line and node models

Effective and widely tested models for the direct evaluation of the residual carrying capacity of the railway networks and the definition of the most effective actions for the full exploitation of this capacity are not yet available. The proposed approach is based on synthetic, probabilistic and combinatory models for links and nodes, interacting each other, sensible to the performances of the signalling systems and not depending upon the timetable structure. Traditionally the link models require the knowledge of the train succession and the node models are based on the hypothesis of independence by the surrounding links. In the paper the limits of this independence are analysed and the effects of the interaction between the network elements (links and nodes) are formalised. The resulting model allows to evaluate the carrying capacity of each single node of a railway network taking into account the effects of the surrounding links and nodes. Of course the combination of these effects influences the carrying capacity of the network itself, which can be evaluated. The effectiveness of the model has been successfully tested on the urban railway network in Rome and the results of the pilot applications have been validated by means of experimental measures.