Mathematical modeling of air pollution in city tunnels and evaluating mitigation strategies

A mаthemаtical model has been developed that is able to describe the environment of the city tunnels being affected by the road traffic, natural and forced air convective flows. The mathematical model describes the peculiarities of the traffic flows on one-lane roads with a satisfactory accuracy. The model well matches experimental data on traffic flows. Multidimensional calculations of the influence of cars on the airflow in tunnels are performed. The numerical model for simulating exhaust gas emissions by automobiles and their accumulation in a tunnel and evolution with traffic induced air flow was developed. The results of numerical investigations make it possible providing recommendations for transport researchers and policy-makers. In particular, it was shown that in the presence of long tunnels on automobile roads it is necessary to choose the traffic arrangement avoiding the necessity for vehicles to come to a full stop and then accelerate in tunnels. This could happen in the presence of traffic lights or other type of traffic regulation near the exit of the tunnel. Thus it is necessary in arranging traffic regulation avoiding placing traffic lights in the proximity of tunnel exit for the waiting cars line to be shorter than the distance from the tunnel exit. In venting the tunnel, the direction of the wind should coincide with the direction of traffic flow. Attempts to arrange venting in the opposite direction for high blockage ratio of a tunnel by vehicles could result in bringing to a worse situation with air pollution.