A GIS-based methodology to estimate the potential demand of an integrated transport system

In the design of a new public transport system or of an extension of an existing system, the choice of a suitable placement of stations and stops in the territory and the definition of the main axes are very important. The different choice in the number and distribution of the stops of a road transport system or of a railway transport system, in fact, makes the system more or less widespread and affects the consistency of the catchment area and the attractiveness of the system. The accessibility of a system, add to the reliability in providing the service, is the fundamental parameter influencing the modal split of the users. Therefore, the Public Administration must have tools able to evaluate different scenarios. The GIS (Geographic Information System) is the natural environment for viewing, managing and editing of geo-referenced data, so it can be effectively used to assess the accessibility of a public transport system and its catchment area. Moreover, it allows to compare different design scenarios, determining the induced benefits and analyzing the critical aspects; GIS is therefore a useful decision support system for Public Administration, directing choices on the basis of objective evidence. The purpose of this paper is to illustrate a GIS-based methodology to estimate the potential demand, in terms of resident population and employees, of an integrated public transport system. As a case study, the integrated public transport system of the City of Palermo has been analyzed, including the tram system and the urban railway system.