An integrated application of zoning for mobility analysis and planning: the case of Paris Region

Overview & Synopsis

In most transport planning studies one of the first steps is the definition of a zoning scheme with which the study area is divided and the corresponding space is disaggregated. There are no clear rules on how to carry out this operation in an optimal way, and the dominating practice is to do it based on experience, trying to mix a certain degree of within-zone homogeneity and the convenience of using administrative borders as zone limits. Firstly, this paper starts by presenting a set of quality criteria for a general zoning scheme and an algorithm that constructs an initial zoning based on a sample of geo-referenced trip extreme points and improves it in successive steps according to those criteria. This kind of zoning fits perfectly well to traffic assignment purposes. But this paper will investigate an improvement of this approach in order to give a better understanding of the mobility determinants and its externalities on the environment. In doing so, the new zone is determined not only by the trips generation and distribution but also constrained by other indicators. In our case, we have selected a combination of the following: 1/ air pollution emissions, 2/ population density, 3/ work and study density and 4/ public transport accessibility. The integration of these 4 indicators allows us not only to picture the mobility within the region and to identify at the very precise level the main zones of activities and traffic exchanges. This integration relates the picture to the land use and the clustering of the economic activities location at a very discrete level. Furthermore, it relates the density of the mobility in dense, large and economically dynamic urban area to its externalities in terms of air pollution. In order to be effective for mobility analysis and policy purposes, this kind of approach cannot only rely on the cell grid unit but a hierarchical aggregation should be set up. This aggregation allows analyses within the administrative and political boundaries but with a more disaggregated perspective. A case study based on the Mobility Survey for the Paris Metropolitan Area in 2001 is developed to illustrate this new approach to zoning. The magnitude of those resulting improvements is very significant especially when compared with the already existing zoning as the department zoning or the IAURIF zoning. It then shows that more attention should definitely be given to this initial process in the transport planning studies.