Service reliability analysis of a tramway network

A promising approach to the analysis of complex technological network systems and critical infrastructures comes from the findings of Complexity Science. The underlying viewpoint is that the stability and robustness of a network system depend on the redundant wiring of the functional web interconnecting its components. In addition to the classical topological indicators, by considering the 'reliability distances' among network nodes in terms of the probabilities of failure of the interconnecting links, global and local reliability efficiency indicators can be defined for use in the analysis of the robustness and vulnerability of network systems and thus for their optimal design, operation and management. This paper presents the analysis of the tramway network system of the city of Milano, Italy, whose reliability is defined with respect to the probability of timely servicing. Both topological and reliability modifications are applied to the original network configuration to analyze the corresponding changes in the service reliability efficiency of the system.