Externalities and External Costs in Transport Planning

The concept of “externality” is adopted broadly within the transport literature. By definition, an externality arises when the actions of a subject have an impact on one or more other subjects, and when such impact is not (fully) compensated for by the first subject. This chapter dwells upon the main externalities (including the positive ones) in transport, upon their effects and briefly, upon the methods that can be used to estimate their economic impact.