Modelling the Distribution of Transport Pollutants in a Naturally Ventilated Road Tunnel

Construction of urban road tunnels is very beneficial for traffic conditions in the urban road network, and also allows a better development of urban space. However, the use of tunnels is subjected to a number of technical requirements specified in the relevant legislation. One of them is the demand for effective air exchange to comply with standards for the permissible concentration of harmful substances and good visibility. In shorter tunnels, natural ventilation may be used, with the driving force being the pressure differential at the tunnel portals and the movement of vehicles inside. The paper proposes a theoretical model to estimate the level of pollutants in a tunnel with natural ventilation depending on the traffic condition. The results indicate that although in longer tunnels the installation of a mechanical ventilation system is mandatory, the periods during which natural ventilation alone can provide sufficient internal environmental conditions are relatively long.