Research On The Optimization Of Bus Priority Control At Signalized Intersections Based On Cooperative Vehicle Infrastructure System

With the acceleration of urbanization in China, the urban traffic congestion problem is growing. The bus priority control plays one of the important roles of improving public transportation efficiency through the technical means and alleviating urban traffic congestion. The rapid development of the Cooperative Vehicle Infrastructure System(CVIS) offers more sophisticated means of acquiring parameters for bus priority control, for rational coordination of vehicles and people, vehicles and road, vehicle and the other vehicles, and provides environmental foundation of the bus running status and two-way intersection timing parameter optimization.In order to further study of intersection signal control problems under the condition of the CVIS, the method of green loss equilibrium is suggested in this paper, combining the data environment that provided by the CVIS, to reduce the total per capita intersection delay as the goal, the bus priority control optimized problem is studied with bus priority single point of control in the condition of the CVIS and the intersection of green wave coordinate. The main studies and conclusions as follow:(1) A method is proposed for the green loss equilibrium at intersections which is controlled by bus priority signal. For the green impact of adjacent non-prior phase by bus priority control, through the analysis of three strategies on bus priority control, which are green extension, red truncation, and prior phase insertion, the methods of green loss equilibrium which is caused by those strategies are also presented, the side effects could be passed to the neighboring phase in the whole cycle. For a bus priority control under the condition of CVIS, the strategy is proposed for accelerating vehicles’ guiding speed and phase timing parameters optimization.(2) The calculation model of intersections delay which faces to bus priority control is established. The calculation model of intersections import delay is presented with considering the cumulative-departure process of the static traffic flow running under the signal control, as well as the starting and spreading process of traffic flow in the queue of entrance road, using the geometric method and the delay overlay analysis. A delay calculation model for green wave coordination intersections is established, describing the delay expectation of the straight and-right turn vehicles in and between the green wave bands, by using the non-set method.(3) The optimization model for green loss equilibrium caused by the bus priority control is established. In the control of intersection bus priority control, using the continuous relationship among different phases of intersection, the green losses are balanced in the whole cycle, which could maximize reduction the strong impact on the intersection signal by the bus priority control. A signal-planning optimization model of bus priority intersection, making the maximum decrease of the total per capita intersection delay at intersections as the objective function and shortest green light time at every phase of intersections as the constraint is established with the considering of the green loss equilibrium, and the model solving algorithm is proposed.(4) The frame of bus priority control under the condition of the CVIS is established. The function of CVIS coupling with the requirement of bus priority control is analyzed, the frame of bus priority control under the condition of the CVIS is established, which integrates vehicle detection, vehicle-road communications, signal control subsystems. Combined with the bus passenger station spacing distribution and with each site real-time charge amount of data, the bus real-time capacity calculating method is suggested with a mathematical expectation model. A fitting function of the arriving vehicles in intersection imports is established, which based on the least squares fitting method. So, a method is proposed for calculating of bus priority control key parameters in the condition of cooperative vehicle infrastructure.(5) The model of the bus priority control that is under the condition of the CVIS is established. The mutual effect on bus speed guidance and adjustment of timing parameters at intersections is fully considered, and combining the strategies of green loss equilibrium in every phase, with combination optimization, a bi-level programming model of bus priority control that is under the condition of the CVIS is established. The decision variable of the model is the bus guiding speed, and the dependent variables are green loss equilibrium parameters of every phase at intersections. Separately considering the buses delay increase or decrease in upstream sections and downstream intersections, the delay changes of non-priority phase referring to the length change of green left and right side caused by subsequent intersection group within the green wave band and between the green wave bands are calculated. A bi-level programming model with combination optimization is established, in which the optimization process of buses’ passes benefit with the bus speed guidance is described in the super-stratum, and the optimization process of general delay at intersections with the bus priority control is described in the sub-stratum.The example calculation results show that the model of bus priority control can effectively reduce the side impact of the adjacent phase green light time loss caused by bus priority control, meanwhile the intersections’delay is decreasing. The bus traffic efficiency is further improved and the side effect of intersection signal control by bus priority strategy is reduced through the collaborative optimization of bus speed guidance and intersection timing parameter adjustment under the CVIS. Under the condition of green waves coordinate intersection group, the bus priority phase time lengths adjustments influence the coordinated relations of adjacent intersections. The side effect of around intersections by bus priority is reduced through the collaborative optimization of bus speed guidance and intersection phase equilibrium parameters.