Marina van Geenhuizen is Associate Professor in the Section System Innovation and Regional Development, Faculty of Technology, Policy and Management at Delft University of Technology, Delft, The Netherlands. Aura Reggiani is Professor in Economic Policy in the Department of Economics, Faculty of Statistics at University of Bologna, Italy. Piet Rietveld worked at the International Institute of Applied Systems Analysis (Austria) and was research co-ordinator at Universitas Kristen Satya Wacana in Salatiga, Indonesia. Since 1990 he has been Professor in Transport Economics at the Faculty of Economics, Vrije Universiteit, Amsterdam. He is a fellow at the Tinbergen Institute. He is also the head of department of Spatial Economics and chairman of NECTAR.