Evidences of communicating vessels principle in results of a regional land use and transport integrated modeling application

Abstract

This article presents part of results obtained from an integrated land use and transport regional modeling, using the simulation software Tranus. Specifically, this research aimed to analyze effects of a regional Transit Oriented Development plan, applied to the French region of Nord-Pas-de-Calais, with reference to the evolution of modal share between private car and public transport and of residential and activity location dynamics. In particular the model has provided results that show the existence of a system of mutual interdependence in transport modal share evolution. This interaction entails the activation of a substitution effect in transport demand distribution, as a consequence of the application of interventions discouraging car use and reinforcing public transport supply performance. Furthermore we also observed some evidences referable to a process proper of the physical principle of communicating vessels. In particular the increase over simulation times of modal share related to public transport, resulting in the application of TOD policies, produces in some zones of the model, a progressive desaturation and decongestion of the road network and therefore a gradual return of attractiveness for private cars. This phenomenon of communicating vessels related to transport demand evolution, indicates the presence of a permanent state of tension in modal share, depending on some particular factors (segment of demand; temporal and territorial context; structure of transport network) and generally tending to a temporary equilibrium. These results invite therefore to observe how policies that promote and encourage the use of public transport may have, in some particular contexts, controversial effects and sometimes contrary to expectations, especially in the long term. The article explains the principles behind the research that have allowed achieving these results, analyzing causes and consequences related to the observation of the phenomenon of communicating vessels applied to dynamics of mobility and transport.