A stochastic model of emission expansion for an urban road

On urban roads, vehicles continuously emit gases and through diffusion, vehicle turbulence, heat flux and by wind the emission can transfer to the upper stratosphere and to the road surroundings. There will be some pollutant that can not transfer instantaneously due to wind velocity or road canyons. For a certain time there will be some pollutant in the road surroundings. This paper formulates a stochastic model of this quantity of gas, and the concentration of expanded gases in any particular area around the road in any time period. More precisely, the paper deals with the effects of street canyons on the dispersion of pollutants from the road environment. A mathematical model has been established to figure out the real situation of pollutants in urban roads. The model consists of traffic flow, emission and dispersion models, and wind speed modeling near the road. The principal part of the model predicts the total pollutant concentration near the ground which includes direct vehicle emissions, pollutants which have not transferred and pollutants coming from the surroundings. The prediction was performed using a bivariate normal probability density function. The variables are concentration of pollutants and wind speed. The pollutant included in this model is nitrogen oxides (NO_x)