Measuring the relationship between public transport share, urban sprawl and car ownership[Motorisation et localisation : quels effets sur le choix du modal ?]

It is widespread acknowledged that car access and urban sprawl are related to each other and that they both influence modal choice. Nevertheless, few methods have the ability to correctly account for these correlations. In this perspective, the method proposed by BONNEL (2000) is quite unique and relevant since it allows separating the effects of each variable. Up until now, the method has been applied and validated using Lyon and related household survey data as a case study. The purpose of this study is to transpose the approach to a North-American city. This experimentation, on the one hand, allows identifying and measuring the respective influences of locations and car access on the evolution of transit in Montreal. On the other hand, it allows comparing the results from the two cities and discussing the ability of the method to clarify this issue in various urban contexts. The microdata from the large-scale origin-destination household surveys held in the Greater Montreal Area are used for this purpose. This experience confirms that the mathematical approach proposed by BONNEL is capable of distinguishing between the respective impacts of the examined variables. Hence, it also confirms that urban sprawl (with respect to trip ends) has a more important impact than the increase of car ownership on the share of transit. Now that its consistency has been demonstrated with two independent sets of data, the method can be used and developed in various ways, namely by introducing new variables (transportation supply), splitting the population into significant segments or using a more precise zoning system.