**Acknowledgment**

This work was performed within the French National Project METAPHORT (ANR VTT 2009 Program) and in the frame work of the North of France Regional Cluster CISIT (Campus International Sécurité et Intermodalité des transports). This work was also supported by the French Research Agency, the Nord pas de Calais Region, ITRANS railway cluster, Images et Réseaux cluster of the Brittany region as well as the French ministry of research and the European Commission (FEDER).
