A Framework Model to Estimate Diverted and Induced Demand for High-Speed Rail: A Test Case from Mixed to Exclusive Service

High-Speed Rail (HSR) has established worldwide as the most sustainable way to travel on a national scale. HSR, as a new mode-service, generates, over time, different travel demand components: diverted, i.e., demand already present along origin-destination pairs; induced, new demand, as an increase in the current frequency or in new origin-destination pairs; and economic growth demand generated by the economic development of the territory determined by the implementation of the HSR, which manifests itself after years of operation of the HSR. The research investigates how HSR services, achieved through dedicated lines, influence both diverted and induced demand, addressing the lack in the literature of a common tested methodology for estimating, in the same framework, diverted and induced demand. Considering the increasing expansion of railway lines worldwide, this study examines the impact of new HSR infrastructure on travel demand, analyzing the two main components that are expressed as the infrastructure becomes operational, with dedicated services. This study proposes a multi-level framework for estimating diverted and induced demand components with an application to a case study on the Rome-Reggio Calabria axis in Italy, where mixed services, operating actually on both conventional and dedicated lines, are already in place. Data have been collected through a combined Revealed and Stated Preference survey. The results of this experimental test allow the validation of the framework model. The interpretation of experimental data reveals an increase in diversion and in travel frequency related to the reduction of travel time generated by the introduction of a new HSR line. This research provides insights for policymakers, transport planners, and researchers, supporting the planning of HSR systems and their integration into sustainable mobility strategies.