The main aim of this paper is focused on the ventilation system in a road traffic tunnel in the moment of an accident situation as a fire. The paper gives an overview of the innovative approach in a field of planning and fire protection of the road traffic tunnel. During the planning and design of the ventilation system, it is important to take in account the fire intensity and it is necessary to provide safe evacuation of people from the tunnel tube. One of the main requirements of a ventilation system is to be able to provide the necessary - critical speed of air flow from the fan to prevent smoke penetration along the zone of passenger evacuation. For this purpose, software has been developed to provide necessary conditions and requirements in accordance with the geometry of the tunnel tube and dispositions of fans inside the tunnel. This paper presents the numerical simulation of fire, and a critical air velocity depending on the intensity of the fire, as well as the output software results developed for this purpose, that are used in the realization of practical projects.