This report includes the Proceedings of the 6th International Symposium on Tunnel Safety and Security (ISTSS) held in Marseille, France, 12-14th of March, 2014. The Proceedings include 59 papers given by session speakers and 10 papers presenting posters exhibited at the Symposium. The papers were presented in 17 different sessions. Among them are Security, Explosions, Risk Analysis, Evacuation, Fixed Firefighting Systems, Passive Fire Protection, Fire Safety Engineering, Emergency Management, Ventilation, and Fire Dynamics.

Each day was opened by invited Keynote Speakers (in total five) addressing broad topics of pressing interest. The Keynote Speakers, selected as leaders in their field, consisted of Magnus Arvidson, SP, Sweden, Kees Both, Promat International NV, Belgium, Peter Sturm, Graz University of Technology, Austria, Jaap Weerheijm, TNO, The Netherlands, and Daniel Nilsson, Lund University, Sweden.