Critical issues in the design of contractual relations for transport infrastructure development

The increasing use of Public-Private Partnerships (PPP) arrangements in the provision of transport infrastructure seems to be a trend all over the world with a very particular incidence in Europe. The arguments supporting these public decisions are several and their validity varies with the different realities where these instruments are applied. The paper highlights the critical issues around the design and implementation of PPPs in the transportation sector and makes a brief presentation of the rational behind the structure of papers presented in this special issue.