EMILE QUINET is Head of the Economics and Social Science Department at the Ecole Nationale des Ponts et Chaussées, Paris, and a Member of the Conseil Général des Ponts et Chaussées. His books include Infrastructures des Transports, Analyse economique des transports and Infrastructure de transport at croissance.ROGER VICKERMAN is Professor of Regional and Transport Economics, Director of the Centre for European, Regional and Transport Economics, University of Kent at Canterbury. His books include Spatial Economic Behaviour, Urban Economies: Analysis and Policy, Infrastructure and Regional Development and The Single European Market.