| With the increasing number of motor vehicles,the rapid growth of fossil energy consumption and motor vehicle emissions has brought great challenges to energy demand and the urban transportation environment.At present,the emission of motor vehicle exhaust pollutants has become the second largest urban traffic problem after road congestion,and as environmental problems become more prominent,people have increasingly higher requirements for the sustainable development of urban transportation.In addition to improving the operation quality of motor vehicle to reduce energy consumption and travel emissions,traffic management is also an important method to solve urban traffic pollution emissions.Considering that traffic assignment is an important theoretical support for traffic management,this paper analyzes the network equilibrium state of road network emissions based on dynamic traffic assignment,and provides a theoretical basis for solving urban traffic pollution emissions.First of all,based on the triangular traffic flow macroscopic fundamental diagram and the cumulative arrival-departure curve of the road vehicles,the trajectory of the vehicles passing through the bottleneck segment is analyzed.The vehicle trajectories were divided into free flow section state and congested section state,and the vehicle emissions under the two states were calculated respectively.At the same time,a simplified acceleration model based on statistics is introduced to describe the vehicle acceleration characteristics from a macro perspective,and then a link emission model based on the modified average speed is obtained,so as to more accurately calculate the vehicles’ emissions through the link.Secondly,the cumulative arrival-departure curve is used to describe the demand and supply of the link,so that the dynamic network loading process is naturally integrated with the link emission model.In the analysis of link emission,the link marginal travel emission is obtained by graphical method,and then the path approximate marginal travel emission is obtained by accumulation.On this basis,two network equilibrium models of dynamic user optimization based on emission target and dynamic system optimization based on emission target are established,and both models are expressed as variational inequality and solved by fixed point algorithm.The performance of the models is verified by an example.Finally,on the basis of the models proposed above,two emission management methods,emission charging and road speed limit,are proposed to provide reference for the actual traffic emission management. |
