Combinationrial Optimization Of Regional Traffic Assignment And Signal Control

With the rapid development of social economy and the acceleration of urbanization process,the number of motor vehicles in cities is growing rapidly and consequently leads to the increasing traffic load of urban traffic network,which has a serious impact on people’s daily life,such as frequent congestion in daily travel,decreased air quality,and increased travel cost of residents.Signal control and traffic assignment are two common methods to solve these problems.The coordinated operation of traffic control and driver route selection can effectively reduce travel delays and improve traffic efficiency of urban traffic network.Therefore,it is of great significance to study the combinationrial optimization of traffic assignment and signal control.First,this paper respectively proposes a traffic assignment model that meet the principle of user equilibrium and a signal control optimization model.The corresponding algorithms are given.Second,this paper proposes a bi-level programming model for the combined optimization of traffic assignment and signal control.The upper level is a signal timing optimization model.It establishes the objective function of weighted synthesis of vehicle control delay,average delay per unit time and road travel time,in order to minimize the total travel time of road network users.The objective of the lower is to achieve user equilibrium in the region.For the proposed optimization model,an iterative optimization heuristic algorithm is proposed.Specifically,the upper model is solved by bee colony optimization algorithm.The lower adds the delay in the form of penalty value that caused by signal control into the impedance function,and thus obtains a new comprehensive impedance function.Based on the Frank-Wolfe algorithm,the lower model is solved by the improved Frank-Wolfe algorithm.In order to analyze the effectiveness of the combinatorial optimization model,it is compared with the two-stage model.The two-stage model does not consider the interaction between traffic assignment and signal control,but only provides the equilibrium traffic flow obtained from the traffic assignment model as input to the signal control optimization model.Numerical results show that the proposed combinatorial model is superior to the two-stage optimization model.