Design of Hybrid Rail Services on Conventional and High-Speed Lines

Almost 60,000 km of high-speed lines are currently in operation worldwide, and around 90,000 km are under construction or planned. A conventional network exists in countries where the high-speed rail (HSR) network is implemented. One of the most important operating models is that which considers the use of HSR-type rolling stock also on conventional networks to produce high-quality services. The problem of designing services that operate on the two types of network is faced at a heuristic level by the different companies that manage railway services. it is therefore useful to have a design model that allows to obtain the optimal solution, with unchanged infrastructural resources. The method used is developed starting from the analysis of the services currently operating on the two networks, building a synthetic graph composed of the macro-links representative of the services existing on the two networks, optimizing the number of stops and the stop time on each macro-link. On the synthetic graph it is possible to obtain the optimal design solution by applying Bellman's theorem. The method is applied to the Italian HSR and conventional networks by studying a new service, referring to the Southern Italy. The results are interesting because compared with the services currently available, they make it possible to optimize travel times, significantly reducing. The lesson that can be drawn is that as all countries build new HSR sections, they can increase user utility by offering high-quality services that use the two networks in an integrated way.