In most developed countries, total car driving is stagnating since the early 2000s. This trend can be attributed primarily to people living in the largest urban areas: trips have become less frequent (with unbroken workdays) and less exclusively taken by car (as more young adults adopt multimodal behaviors). A review of the literature shows that demography is an important factor explaining peak car. It is examined through case studies from cities of different level of development. To represent developed economies we chose Lille in the North of France, and Montreal in Canada. For the emerging economies we chose two Mexican cities, Juarez, on the northern border of Mexico where the level of motorization is quite high, and Puebla more traditional, where car ownership is lower. A straightforward combination of fixed mobility by age group with the evolving number of inhabitants suggests that the demographic transition (i.e. a slower growth of the number of inhabitants with population ageing) shows a peak in the total amount of car travel. Then, considering travel behavior in terms of distance travelled per person per day, an age-cohort demographic projection model is implemented for each case-study in order to consider the extent to which, and in what time frame, the trends observed in developed cities could spread southward to the emerging economies.