Research On Transit Priority Control Scheme Of Pre-signalized Intersection Based On Contraflow Left-turn Lane

In order to alleviate urban traffic congestion,some scholars proposed the transit priority strategy,which has been widely used in urban roads and intersections.Transit signal priority control is one of the important methods to implement transit priority at intersections,which makes buses pass through intersections quickly,saves passenger travel time,effectively improves the attractiveness of public transit,and further optimizes the traffic structure of urban passenger transport.However,the setting of the pre-signal will make the traffic order of social vehicles fall behind,and increase the waiting time of social vehicles.Moreover,vehicles from all directions have more conflict points at the entrance of this type of intersection.The mutual avoidance of vehicles will lead to further expansion of the total delay at the intersection.At the same time,at most pre-signalized intersections,only straight-going buses are prioritized,and the method is not applicable to intersections with a large flow of left-turning buses.Based on this,this paper intends to transform the pre-signalized intersection,and proposes a bus priority control scheme of the pre-signalized intersection based on contraflow left-turn lane,which is realized on the basis of ensuring transit priority,and make the left-turning social vehicles and left-turning buses pass through the intersection at the same time,which will improve the intersections’ space utilization and traffic efficiency,reduce the average person delay,and reduce the adverse effects of setting pre-signal on social vehicles.In order to understand the bus priority control process at pre-signalized intersections,the first part of the basic work of this article is to gain in-depth knowledge of bus priority at presignalized intersections,including the layout of entrance lanes,traffic flow organization rules,and the coordinate control methods between main signals and pre-signals.The pros and cons of the existing methods are analyzed to lay a theoretical foundation for the introduction of the left-turn design method for this paper.Therefore,the second part of this paper focuses on the study of the design of presignalized intersections based on the left turn.On the basis of a comprehensive understanding of the design idea of the contraflow left-turn lane,the form of the inlet road and the phase organization method,combined with the existing pre-signalized intersection design considerations,the setting conditions of the spatial layout,signal timing,traffic volume and lane function division of this type of intersection are determined.Finally,this paper take the traditional cross signalized intersection as an example,and propose the intersection geometric layout and phase design scheme.The optimization goal of this research is to achieve transit priority.The key work of the third part is to study the transit signal priority control model and algorithm.Assuming the vehicle arrival rate in each approach method obeys uniform distribution,based on car flow organization,the intersection delay calculation model is constructed by using cumulative arrival-departure curve method.The signal timing optimization model is established to achieve the minimum average person delay of the intersection with the consideration of the constraints,such as cycle length,saturation,main and pre-signal control,and functional section length.And the optimization algorithm steps of transit signal priority control model based on simulated annealing algorithm are also proposed.The last part of the research is to design an numerical example to verify the effectiveness of the proposed method.Firstly,the geometric layout and signal timing scheme of the example intersection are reformed and optimized according to the method of this research,and the average person delay,vehicle delay and intersection capacity of the example intersection are compared with the conventional intersection and the tandem intersection.The result shows that under the condition of intersection saturation of 0.85,compared with the conventional intersection and tandem intersection,the proposed method can effectively reduce the average person delay of intersection and improve the traffic capacity.According to the sensitivity analysis results,the effect of this proposed method on reducing average person delay is more obvious with the increase of vehicle arrival rate.And it can also perform better when the proportion of through bus is 25% ～ 35% or of left-turn bus is 15% ～ 25%.In practical application,the length of the functional sections such as the comprehensive waiting area and the transition section at the entrance should be better taken the minimum critical value.