Abstract
The necessity to monitor and regulate the traffic flow in high density traffic tunnels is clear from the following data derived form the surveillance of a German motorway tynnen during several years: three times a day some vehicle breaks down, twice a day a too high vehicle is stopped, once a week an accident happens and twice a month a vehicle catches fire. Some of the necessary instruments to detect and regulate are: changeable speed limit signs, loudspeakers, cameras, monitors, traffic signals, computers, ground plans, radio, induction loops. The article covers all the necessary measures for different kinds of tunnels.