The safe operation of tunnels requires a fast and reliable incident detection. Only precise information about the place, type and extent of the incident allows for a selective launch of measures, e.g. regulation of the ventilation system for smoke control in case of fire, or the halting of traffic outside and inside the tunnel following an accident. This paper discusses the use of digital video analysis in incident detection. Using appropriate evaluation logarithms, available computing capacities allow for an analysis of video data in real time and, at the same time, to automatically detect the type and extent of the incidents as well as their spatial and temporal causes. In addition to traffic data such as traffic flow, traffic density and speed, video imaging can detect the following incidents: formation of fire and smoke, stopped vehicles, ghost drivers, changes in illumination, and use of hard shoulders by emergency response teams. Online analysis of the video data then makes the direct and selective control of operating functions possible immediately following the incident occurrence. A further advantage of digital video analysis lies in the storage of recorded data, which can serve in the subsequent reconstruction of incidents.