Evidences of communicating vessels principle in an integrated land-use and transport modeling application

This article presents an integrated land use and transport modeling application to analyze effects of a regional plan for Transit Oriented Development, using Tranus simulation software. Part of the results shows the existence of a system of mutual interdependence in transport modal share evolution. This interaction firstly results in the activation of a substitution effect in the distribution of transport demand between private car and public transport, and then in a process corresponding to the principle of communicating vessels. This phenomenon 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. 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.