The city of Frankfurt am Main is located in the heart of Europe. The urban area covers a surface of 248 km2. The city's original population ranges around 655.000 people. In addition to that, more than 360.000 commuters enter the city every day, so that in day times there are more than 1.000.000 people in town. The following tunnels are under the jurisdiction of the city's fire department: two street tunnels, rwo railway tunnels and two metro systems. As a conclusion from the recognized problems and causes it is possible to define the objectives to reach an appropriate level of safety. The main objectives are: minimize the danger of a fire breaking out, guarantee a rapid activation of the fire alarm and fire fighting operations, enable endangered people to save themselves, and guarantee the others to be saved by the fire department limit the fire to the smallest possible area, minimise consequential damage to the tunnel construction and possible disruptions of the vehicle service. In the paper the overall concept to achieve these objectives are presented.