Abstract
The higher concentration of households and activities leads to increase the urban mobility and their associated negative externalities especially with a more use of private vehicles. In Tunisia, households tend to migrate from rural to urban areas and the motorization has known an important rise. The aim of this article is to examine the sustainability of road transport systems in Tunisian mega cities where the urban density is higher and negative externalities have become a serious problem for the population. To this end we examined the relationship between income and several environmental and social negative externalities of road traffic in Tunisia during the 1989-2008 periods by using the Environmental Kuznets Curve. Moreover, we examined the same relationship for the modal choices (private vehicles and public transportation) to study the impact of the urban mobility. Results indicated an inverted U-shape relationship for tow air pollutants: sulfur dioxide and suspended particulate matter. However, we found a monotonically rising carbon dioxide-income relationship and a downward curve with L-shaped for Nitrogen dioxide. For the rest of negative externalities, we detected a monotonically rising energy consumption-income relationship and an inverted U-shape relationship for accidents. Finally, we detected a monotonically rising for the income-use of private vehicles relationship. Some measures should be decided for the variables which EKC is not exist.