ABSTRACT
The relationship between transportation and the environment is paradoxical in essence. On the one hand, the provision of transport infrastructure and services supports the ever increasing mobility demands from passenger and freight flows and simultaneously conveys substantial short- and medium-term benefits both from a social and economic viewpoint. But, on the other hand, the same transportation activities have also become a major source of environmental externalities, whose negative effects could jeopardize the sustainability of those social and economic benefits in the long term. The complexities embedded in this relationship and their undisputable consequences in terms of efficiency and equity have made environmental concerns a critical issue in current transport policies and also help explain part of the relative success and public support enjoyed by high-speed rail (HSR) in recent years around the world.
