Real-time Estimation Of Vehicle Pollutant Emissions And Dispersion In Urban Road

Motor vehicle exhaust emission has become the first source of urban air pollution in Beijing, caused haze and smoking pollution. Urban street area is the most important environment for pedestrian walking. Because of the large number buildings and vehicles in urban street environment, the vehicle pollutants are easy to accumulating and hard to dispersing, therefore the pollutant concentration in urban streets environment is higher than other areas. Pedestrians which walk and expose in air pollutants directly are group who faces the most serious health risk. The actual traffic running status, meteorological conditions and street geometry are the key influence factors of the total emission and pollution degree of vehicle exhaust. Obtaining accurate and real-time pollutant concentrations are difficult due to the spatial and temporal variability of emissions, the dependence on local atmospheric conditions. In this paper, we present a novel air pollution estimation method that models the traffic state, estimates the real-time traffic data. Next, we estimate air pollution emissions combined with vehicle emission factors. At last, we use the dispersion model to estimate the pollutant concentration. We describe a prototype implementation for the CBD urban road of Beijing. This research could provide a novel method for analyzing vehicle pollution degree, establishing emission control strategy.Firstly, we model and simulate the urban road traffic networks based on a macroscopic traffic flow model. The urban road is divided into different cells according to the cell transmission model. The cell transmission expressions of different connections between cells(simple connection, merge and diverge) are defined, and the simulation has been made. The cell transmission model can be used for urban road traffic networks, and describe the traffic states, estimate the real-time traffic data.Secondly, we research the vehicle exhaust gas emission. The vehicle emission factor is the basic parameter to reflect the status of emission and determine the total of vehicle emissions. In order to the regional differences of base emission factors in real application, a method of modifying the emission factors was proposed based on VSP model. We collect the actual driving parameters using a real-time system based on smartphone. We estimate the new emission factors using the actual driving parameters based on VSP model. At last, we estimate the total of pollution emission combined with new emission factors.Finally, we analysis the situation of emission dispersion and simulate the pollutant concentrations. The street canyon is one of the typical street styles in the CBD roads, in which high buildings exist on both sides of the street. The vehicle pollutions are not easy to disperse in such areas due to the influence of the buildings. This paper, we select the OSPM(Operational Street Pollution model), which takes into the impact of the geometry of the street(the street height, width and intensity of the buildings) and the meteorological conditions. The model has a high accuracy. In this paper, we use a model to calculate pollutant concentrations and analysis vehicle pollution degree.