Link-based System Optimum Dynamic Traffic Assignment Problems With Environmental Objectives

As one of the core technologies of Intelligent Transportation System,dynamic traffic assignment theory has a certain application in the study of traffic problems.With the deepening of the research on traffic problems,environmental factors have become one of the most important factors affecting the transportation planning and policy making.In this paper,we study the optimal dynamic traffic assignment problem based on the single destination traffic network with the total system emissions as the research objective.The research work of this paper mainly includes the following three aspects:Firstly,we use step functions to approximate cumulative flow curves for individual links,and to decompose link inflow into sub-flows according to time intervals at which they leave the link.According to the different vehicle classification assumptions,two discrete-time emission models are formulated.And numerical examples are provided to demonstrate the accuracies of the proposed emission models.Secondly,we use the link transmission model(LTM)to develop system optimal dynamic traffic assignment(SO-DTA)models with environment objective in single destination networks,and minimize total system emissions as the objective of optimization.Dynamic network constraints,non-vehicle holding constraints and link inflow decomposition constraints are considered,and SO-DTA problems with environmental objectives are formulated as mixed integer linear programming(MILP)problems.Any average speed based emission functions can be used for our models.And numerical examples are provided to demonstrate the performance of the proposed models.Finally,on the basis of the above model,we consider the speed limit policy in the LTM,and formulate the choice of multi level speed limits as MILP problems.And non-vehicle holding constraints under the condition of speed limit are considered.Three different speed limits and the corresponding SO-DTA model are proposed.And numerical examples are provided to demonstrate the speed limit effect of the proposed models.