Analysis of principal trends of mobility related to location policy, car ownership, supply policy and ageing of population

In transport analysis, we generally have several correlative explanatory variables when we want to explain the evolution of a factor. Therefore the quantification of the contribution of each variable in the evolution of our study object is often problematic. This problem is well known in modelling even if not always well treated. In this case the evolution of the object cannot always be expressed simply (as a sum or a product) from the evolution of the explanatory variables. To take this question into account, we propose a method to break down and measure the effect of each explanatory variable. We have applied this method to two contexts which focus the thematic network on Society, Behaviour and Private/Public Transport.The first one deals with a retrospective analysis of the evolution of car ownership and car use of both elderly people and younger people. This analysis permits to quantify the contribution of different factors: demographic effect, car ownership effect and behaviour effect and their combination to quantify the evolution of the number of car trips in the population. This analysis has been conducted both in Lyon and Grenoble conurbation in south-east of France from several household surveys conducted between 1970 and 1995.The second one analyses the evolution of the share of public transport among motorised trips in the Lyon conurbation. This analysis allows to quantify the contribution of different factors: urban sprawl effect, car ownership effect, public transport supply effect, private transport supply effect and a residual effect which summarised unobserved variables and their combination to quantify the evolution of public transport share among motorised transport. It explains the apparent paradox of a very important increase in public transport supply in Lyon conurbation but a stability of the share of public transport between 1976 and 1995.Both analysis suggest interesting features both in term of prospective and urban policy. It appears that very strong socio-demographic trends act to reduce, when not cancel, the effect of important improvement in public transport supply as we can see in many French conurbation. From the quantification of different effects, we can simulate different future from which it appears that only global and comprehensive policy on all mode of transport and parking and on urbanism are able to reduce use of car in sustainable perspective.