Study On Particulate Matter Emissions In Cellular Automata Model Of Traffic Flow

With the acceleration of urbanization,the number of vehicles is increasing year by year,which makes traffic congestion increasingly severe.And the increase of vehicles exhaust emissions leads to the continuous decline of ambient air quality.Medical studies have shown that inhaling the particulate matter of PM_2.5in vehicle exhaust can cause cardiovascular and cerebrovascular diseases.Therefore,it is of great significance to study particulate matter emissions in traffic flow.In this thesis,cellular automata model of traffic flow is used to study the particulate matter emissions of traffic flow.The main research work of this thesis is as follows:（1）By combining the vehicle particulate matter emission model and considering the periodic boundary condition and the open boundary condition,the particulate matter emission of several typical traffic flow cellular automata models under metastable state is studied respectively.Under the periodic boundary conditions,the metastable traffic spatio-temporal pattern is obtained by numerical simulation,and the result shows phase separation phenomenon.It was found that the metastable traffic flow emits the most particulate matter for VDR model and BJH model,while TT model had the most emissions in the traffic congestion zone.Under the open boundary condition,the traffic phase diagram and flow diagram are obtained by numerical simulation.The study shows that the emissions of particulate matter are different with the different injection probability and removal probability.Finally,under the two boundary conditions,the influence of vehicle motion state on emissions in each model is studied respectively,which found that the traffic flow in decelerated state emits the most.（2）Based on the cellular automata braking-light（BL）model and lane-changing model of traffic flow,combined with the vehicle particulate matter emission model,the particulate matter emissions of two-lane traffic flow were studied under symmetric and asymmetric lane-changing conditions.The fundamental diagrams and lane changing rates of left and right lanes were obtained by numerical simulation.Through the spatio-temporal pattern and the correlation analysis of local flow and density,synchronized flow in two-lane traffic flow has been confirmed.Under symmetric lane-changing conditions,it is found that the fundamental diagram,vehicle lane-changing rate and particulate emissions of left lane and right lane are the same.Under the condition of asymmetric lane-changing,the flow in the left lane is higher than that in the right lane in the synchronous flow area,but the particle matter emissions in the left lane are lower than that in the right lane.（3）Considering two different types of vehicles,the cellular automata BL model of two-lane mixed traffic flow was proposed by introducing the mixing ratio.Considering the periodic boundary conditions,the particulate matter emissions of mixed traffic flow were studied under symmetric and asymmetric lane-changing conditions,and the effects of different vehicle mixing ratios on system flow,vehicle lane-changing rate and particulate emissions were discussed.Under symmetric lane-changing conditions,the numerical simulation shows that when the vehicle mixture ratio in the system is constant,the flow,vehicle lane-changing rate and particulate matter emissions of both lanes are the same.In the case of asymmetric lane-changing rule,the results show that the flow,vehicle lane-changing rate and particulate matter emissions of both lanes are different when the vehicle mixture ratio in the system is constant.In addition,when the velocity of long vehicles is greater than that of short vehicles,the simulation results under the both lane-changing rules show that the traffic flow increases with the increase of the mixture ratio of long vehicles.When the vehicle lane-changing rate increases,the traffic flow particulate matter emissions increases gradually.When the mixing ratio of vehicles in the system is constant,different vehicle mixing ratios in the left and right lanes at the initial moment have no significant influence on the traffic flow in each lane.