Demand Forecasting models for High Speed Railways: A twenty-years retrospective analys

From Europe to US and to China, Governments and several PPP entrepreneurs are investing in developing High Speed Railways (HSR) networks. In facts, HSR is world-wide acknowledged as a sustainable and efficient transportation mode for intercity medium-haul trips (i.e. 400-800 Km long), although empirical evidences show it could be attractive also for shorter trips (e.g. 150-200 Km long). In Italy major investments in High Speed Railways (HSR) have been carried out in the last decades resulting in a current network approximately 1300 Km long. The HSR service, started in 2005 between Rome and Naples, now includes several city pairs. The level of service is expected to be further improved with the completion of the new stations in Naples, Florence, Turin and Rome that will allow direct service avoiding calls at central stations in dense urban area, and, on the other hand, with the entrance in the HSR market of a new private operator (i.e. Nuovo Trasporto Viaggiatori- NTV), competing with the incumbent Trenitalia. These changes create the conditions in the Italian national transportation market, for a unique case study to investigate the behavior of long-distance passengers. The objective of this paper is twofold. In the first part, we present the results of a study on the HSR in Italy, giving a clear picture of what is the current scenario and what has been its evolution starting from the introduction of the HSR service on the National railways network (i.e. 2007). The analysis is based on longitudinal surveys carried out between years 2008 and 2011 and mathematical models aiming at estimating the impacts of HSR on the modal split, the trip frequency and the distribution of intercity trips, as well as of the changes induced on people lifestyles and land-use patterns. In the second part of the paper we review retrospectively the studies on HSR carried on in Italy dated back to the early Eighty’s, comparing those traffic forecasting to the observed current demand, using a back-casting technique. The review will start considering the modeling approach, the level of zoning of the study area and the segmentation of the demand. Moreover, it will take into consideration the assumptions on the growth of the National Economy and the relative elasticity of the intercity passenger demand; the assumptions on the development of the road network and of the evolution of the air transport and the competing alternative railways services. A specific emphasis will be given to the issue of the induced demand: whether or not it has been considered, and, if positive, how and to what extent