A traffic surveillance system is often installed when the level of traffic is very dense in a tunnel. Usually, a video-surveillance system is used, supplemented sometimes with counting devices. A video-surveillance installation offers the operator the possibility of controlling the traffic conditions in the tunnel in real time. In case of degraded operation, it allows viewing the concerned incident zone so that the needs may be rapidly evaluated.
Video-surveillance is thus a very valuable tool for the operator because it allows him, on the one hand, to watch continuously the incidents inside the tunnel and on the other hand, to react rapidly in case of need. However, in order to make full use of a video-surveillance installation, it is essential to maintain a human presence, if possible continuously, at the control-command centre.
A video-surveillance is generally quite simple in its conception. Cameras placed at regular intervals in the tunnel provide a complete coverage of the tunnel and its surroundings. The images are then grouped and transmitted by networks that may or may not be dedicated, to the control-command centre of the tunnel. The images are then received and viewed on the displays.