1. a Centre for Industrial Management , Katholieke Universiteit Leuven , Heverlee , Belgium
2. b Department of Maritime and Transport Technology , Delft University of Technology , Delft , the Netherlands
3. c Dipartimento di Informatica e Automazione , Università degli Studi Roma Tre , Rome , Italy
4. d Department of Transport and Planning , Delft University of Technology , Delft , The Netherlands