Research On Dynamic Traffic Assignment Under Controlled Road Network

Intelligent transportation system(ITS)is effective for alleviating urban traffic congestion which is a recognized and effective way of traffic demand management around the world.Controlled road network based on intelligent transportation systems technology is gradually developing and the controlled road network can provide realistic foundation for the reconstruction of the traffic flow operation mode based on network platform.In this paper,a dynamic traffic assignment model based on controlled road network was proposed according to the attributes of itself,which is different from traditional dynamic traffic assignment model with the finally and only optimal solution.The paper can assign and control the flow effectively,making the assignment to the network dynamically and reasonably according to the requirements of operators and controlling the flow on the network with fixed time and quantity.The method is aimed to improve the network equilibrium state,reduce congestion and enhance the efficiency of the urban traffic system operation through controlling flow on the roads.This paper has carried on the comprehensive introduction and analysis by combining with the intelligent transportation technology of controlled network,including the network characteristics and the influence on dynamic traffic assignment and determining methods of path selection and its assignment.And then we focused on the analysis of the key sections with the influence on the overall network operation efficiency,and introduce the identification steps according to its status and the role of dynamic traffic assignmentSecondly,this paper developed a way of pre-control,that is,control the flow that will arrive the key sections in advance for the controlling flow on key sections with the considerations of delay of flow assignment,and the flow cannot exceed the predefined value.We can get the period that the flow exceeds the limited value by forecasting the flow on the limited sections with BP neural network.And then get the controlled period according to the travel time from limited section to origins.Finally,combining the above analysis,the dynamic traffic assignment model based on controlled road network was proposed with the goal of optimal system according to optimal control theory.The conditions of the optimal solution and algorithm of solving the model is expounded.A large network was applied to be an example,and the different flow demand were assigned with and without flow limited.The results shows that the flow can assigned to the network effectively and the network can operate effectively when the flow limited were set for key sections,which can avoid the local traffic congestion and potential Internet lock.