A dynamic measurement of the relationship between public transport share, urban sprawl, car ownership and transport supply - Lyon, 1976-1995[Une mesure dynamique des relations entre transports collectifs, étalement urbain et motorisation. Le cas de Lyon, 1976-1995]

In a context where a lot of European conurbations are trying to reduce or to contain car use in urban areas for environmental or economic reasons, this article aims at assessing the contribution of certain major trends to the evolution of modal split between public transport and car. The objective is to quantify these contributions. We examine the effect of urban sprawl and car ownership growth on the share of trip market between public transport and car. In the Lyon Conurbation, during each of the last two decades, the development of localisation of trips explains a decrease of 6 to 9% of the share of public transport depending on decade and study area ; while the increase in car ownership (with a fix spatial structure of flow) explains a smaller decrease between 1 to 4%. This quantification can inform decision-makers about probable changes in the market share of public transport and the importance of certain factors in these changes. It makes it possible to construct more realistic modal split scenarios and assess the scale of the effort that is required if only to maintain the car in its present position with a view to achieving sustainable development.