Fine-grained Estimation Modeling Of Traffic Emission Concentration In Urban Canyons

With the process of urbanization in China,more people gather in megapolis.Buildings with high density causes urban canyons,which would form a wind vortex circulation area,making it difficult for pollutants to disperse.To figure out the relationship between traffic and vehicle emission concentration in urban canyons,estimating the microenvironmental pollutant concentration based on traffic data,this paper proposes a fine-grained integrated model to describe the vehicle exhaust from emitting,dispersing to exposing in urban street canyons.Firstly,this paper comes up with an optimized trajectory reconstruction model based on traffic flow theory with traffic input data including vehicle timestamps,lane information and signal timing,and it outputs the instantaneous speed and acceleration rate by second.The NGSIM datasets are utilized to verify the trajectory reconstruction model accuracy.Secondly,CMEM,a microscopic vehicle emission model,is used to estimate the emission intensity.Then input the emission intensity into OSPM to describe the dispersion mechanism of emissions in urban street canyons and intersections.Finally,the estimated CO concentrations are compared with the observations to verify the accuracy of the integrated model.The result shows the optimized trajectory reconstruction model in this paper could make reconstructed trajectories closer to the ground truth than existing trajectory reconstruction methods did.And when it is coupled with CMEM,the accuracy of emission intensity estimation is not sensitive to the penetration rate of traffic data,which indicates that the trajectory reconstruction method is also feasible when traffic data is of poor quality.In addition,according to the research and analysis of the measured CO concentration,its distribution in urban canyons is different from that in open streets.The concentration of leeward sides is generally higher than it of windward sides,and the difference is larger with higher wind speed,which could be reflected by the integrated model.Also,the model is suitable for estimating the concentration of pollutants in both urban street canyons and intersections,providing reliable data and theoretical support for urban air pollution control and other relevant studies.