Although car ownership is increasing on aggregate in all countries, the net changes mask a substantial variability at the individual household level. At the individual household level, car ownership and car use may increase or decline. Changes in car ownership and use are determined by economic factors, e.g., income and costs, and also by various changes in household circumstances or transitions: changes of residential location or the place of work; the entry into and the exit from the labor force; and transitions in the structure of the household (arrival or departure of a member, or a member becoming of driving age). Of specific interest in this research work package is to examine reductions in car ownership and car use at the household level and to determine the extent to which the reductions could be explained in terms of these transitions.