Centrality analysis for railway network planning: constrained measures for High Speed

High-Speed Rail (HSR) represents a sustainable travel option for serving passenger mobility at a medium–long distances. This research concerns the analysis of HSR with specific reference to transport services at a national territorial scale. The Transport System Models (TSM) lack the capacity to generate synthetic measures and indicators of the transport supply structure. This paper proposes to combine classical TSM approaches and network analysis (NA) focusing on two main research's issues: a) the possibility to develop a method based on NA to study the structure and topology of High-Speed Train (HST) service networks, using classical TSM approach; b) the necessity to specify appropriate centrality measures for a ‘line-based’ transport system. According to the two research's issues, the paper has two main objectives: 1) to propose a criterion for extending, in a systematic way, NA tool to HST services, combining them with TSM approach; 2) to propose an advancement of centrality measures for analysing the level of connectivity between selected territories, by introducing temporal constraints that influence the quality of the connections served by the HSR. Classical and constrained centrality measures can support the planning of lines and their characteristics (e.g., travel times and frequencies). The proposed methodology is applied in a prototypal case study, for analyzing in a synthetical way the HST services available in Italy. The paper interests public and private decision-makers who want to design, formulate and evaluate a national organisation of HST services.