Research On Optimization Of Bus Priority Using Pre-signals At Intersection Based On Exhaust Emissions

In recent years,cities at home and abroad have vigorously developed public transportation,and the strategy of "Public Transport Priority" has become a development consensus.Scholars at home and abroad have conducted a lot of studies on public transport priority strategies from different perspectives.Generally speaking,they can be classified into two categories,one is "time priority",and the other is "space priority".However,the conventional bus priority control methods at the intersection do not fully utilize the time-space resources of the intersection.At the same time,due to the limitation of land resources and the large non-repeatability of engineering construction,it is difficult to carry out substantial reconstruction of the intersection at present.A novel bus priority control strategy,"bus priority using pre-signals",can be a good solution to the above problems under certain conditions.The pre-signals for bus priority control can enable buses to have priority in both time and space resources when crossing intersections.Currently,environmental issues have increasingly become the common concern all over the world,and urban air pollution has become one of the major livelihood issues concerned by people,among which the exhaust emission pollution of motor vehicles is one of the important influencing factors of air pollution.In this context,exhaust emission is introduced into the research of pre-signals for bus priority control in this paper,and a signal timing optimization model is established with the goal of minimizing total emissions at the intersection in order to obtain the optimal signal control scheme,then the validity of the model is verified through case analysis.This paper firstly reviews the current research status at home and abroad from the aspects of pre-signals for bus priority,exhaust emission measurement models and intersection signal control research considering exhaust emission,and points out the shortcomings of the current research,based on which the research objectives and technical route of this paper are determined.Based on the analysis and summary of the application scenarios of the pre-signal,the spatial layout form,operation mechanism,setting conditions,and setting process of the pre-signals for bus priority control are analyzed.Then,by sorting out the classical emission measurement models which are widely used,the MOVES model suitable for measuring the exhaust emissions of intersections is selected.And using MOVES’s measurement principle,this paper established an intersection emission measurement model which can quantify the relationship between exhaust emission,delay and stop time while calculating intersection exhaust emissions more easily.And the validity of the model is verified.Next,in order to minimize the adverse effects of pre-signal settings on social vehicles,this paper proposes the lighting principle of pre-signal which lets pre-signal reds ahead main signal and greens after main signal when studying the coordination relationship between main signal and pre-signal,and improves the operation mechanism of pre-signal.The results show that the method proposed in this paper can effectively reduce the secondary queuing phenomenon of social vehicles generated by setting presignal.Finally,this paper establishes an optimization model of pre-signals for bus priority based on exhaust emission,and the optimized parameters are the period of the main signal and the green light duration of each phase.Then the genetic algorithm is selected as the model solving algorithm.Then the case intersection is applied,and the signal timing scheme of pre-signals for bus priority control to minimize the total emissions of the intersection is obtained.The results show that the optimization model established in this paper can significantly reduce the exhaust emission of intersections,and the reduction of various pollutants is 16%-38%.Moreover,the optimization scheme of pre-signals control can effectively reduce the delay and parking times of public transport vehicles.In particular,the total delay of buses in the straight direction of the entrance controlled by pre-signal is reduced by 70%,and the number of stops is reduced by 21%,while the delay and the number of stops of social vehicles in the straight direction are also improved to varying degrees.