Study On Multi-objective Bus Priority Control Method At Intersection

With the maturity of urban road network,traffic congestion became increasingly serious,It is particularly important to advocate public transport in this context.Intersection is the bottleneck of both urban road system and public transport operation.Considering the method of calculating the green light time under the condition of actuated control,analyzing the state of the intersection when the bus arrives,and considering the arrival time of the bus and the phase display of the bus,this paper proposes an optimization model of the minimum green time for the bus priority intersection,and establishes the multi-objective optimization model which takes both the bus and the social vehicle into account.Based on the priority of bus at intersections,the priority demand grade of the bus at the intersection is proposed and the intersection is used as the node to adjust the on-time rate of the bus.Firstly,the prediction method of bus travel time is analyzed in this paper,and the time when the bus arrives at the downstream station is predicted according to the time that the bus leaves the upstream station.Then this paper puts forward the priority grade of bus demand and decides whether to choose the bus priority strategy according to different grades.At the same time,the range of the adjustment time according to different priority strategies is calculated,which lays the foundation for the later adjustment of bus punctuality rate with the intersection as the node.The value of signal control parameters will affect the implementation of bus priority strategy,but compared with the maximum green time and unit green extension time,the minimum green time has a greater impact.If the value of the minimum green time is not appropriate,the signal control will lose the priority opportunity.Therefore,the impact of the minimum green time on the per capita delay at intersection is analyzed in this paper.From the point of bus priority,considering the randomness of vehicles arrival and the relationship between bus and non-bus phase,the delay of vehicles arriving at the red time is calculated.With the goal of minimum per capita delay,a model is established by taking the bus priority strategies and the random demand of the green time as the constraints,the corresponding algorithm is given,and the correctness of the model is verified.Considering the impact of different priority strategies,the calculation formulas of each objective are derived when using bus priority strategy.Based on the priority demand grade of the bus,aiming at the minimum incremental of average delay of non-bus phase vehicles,the minimum per capita delay at the intersection,and the maximum optimization rate of bus delay time,taking the relationship between the objects and between the constraints into account,a multi-objective optimization is established and the genetic algorithm is used to calculating the green time of each phase.The model idea is that while improving the operation efficiency of the bus priority direction and advanced the optimization rate of bus delay time,minimized the impact of bus signal priority on average vehicle delay in non-priority direction.Based on the actual case,the priority demand grade of the bus at the intersection in this case is given,the relationship between different optimization goals of the model and the bus delay time is explored,and the model effect is analyzed.On the premise of taking priority strategies,the lowest optimization rate of bus delay time is 10% and the highest is 90%,while the per capita delay at the intersection and the incremental of average delay of non-bus phase vehicles do not change much,which is within the acceptable range,which shows the model is effectives.The studies show that the per capita delay at the intersection,the incremental of average delay of non-bus phase vehicles,and the optimization rate of bus delay time are closely related to the delay time of buses,the priority demand level of buses and the strategies of bus priority.After comprehensive analysis,it is concluded that the priority level of bus demand defined in this paper is consistent with actual traffic control,and the multi-objective optimization model based on the single-objective optimization model can not only guarantee the priority of buses at the intersection,but also take the overall benefit of the intersection into account.