Research On Urban Regular Transit Real-time In-station Dispatching Strategy

Urban public transportation is one of the main effective measures to solve the urban traffic problems.However,urban bus routes,especially nomal bus transit,are affected by various external factors.This often causes that bueses can not travel in accordance with the schedules and the bus headway variation becomes large.This would not only lead to lower operation efficiency of public transport,but also reducing the transit service quality.In this paper,taking the nomal bus transit as the research object,based on the real-time data,the bus headway variation as the breakthrough point,under the premise of bus headway variation affecting factors,three real-time bus in-station dispatching strategies,which are holding strategy,stop-skipping strategy and the hybrid strategy,are modeled and studied using decision-making theory.The purpose of this paper is to manitain the stability of bus headway and to reduce the passenger waitng time to improving the transit service.Firstly,the impact on bus actual departure frequency and transit service quality by bus headway variation is analyzed theoretically.Then the method for evaluating the bus headway and its distribution characteristics are introduced by the real data in Harbin.And the abnormal bus headways are identified using statistical theory.Thus a method integrating Data Mining and AHP is proposed and 6 stop-level influence factors,which cause the variation of bus headway,are determined,as well as their weights.These findings would provide more targeted and valuable guidance for studying holding,stop-skipping and the hybrid strategy.Secondly,taking the starting station as the control point according to the findings above,a real-time bus holding strategy is proposed using stochastic decision.The travel time between stops and the dwell time at stops are treated as random factors during the decision-making process.Holding strategy is implemented for dispatching buses at the first station with the objective of minimizing the expected variance of the bus headway fluctuation and the decision variable of holding time.To solve this problem and obtain the optimal holding time and departure time,dynamic programming is used to decompose the multi-stage decision problem into a single stage decision problem.The numerical results show that the proposed holding strategy is applicable for different transit demand and it can easily recover from the interfere.Note that,when the interruption is serious enough,the holding strtegy would prodce a terrible long headway.Thirdly,considering the problem of holding strategy,the real-time stop-skipping strategy is studied to deal with serious interruptions.The integer programming models are construted for two kind of stop-skipping.An exhaustive method is used to solve the models because there are not many stops for a bus line in the real world.The dynamic evolution of picking up and deliverying passengers is analyzed in deail and the optimal stop-skipping scheme is obtained.To insure the strategy is always optimal for the current state,a adaptive decision is used which could update the latest data real-time.Unfortunately,the stop-skipping strategy is applicable for serious interruption,rather than the normal random interference.Then,a dynamic objective function including the predictive effects of any strategy is proposed considering the disadvantages of holding and stop-skipping strategies.Then the nonlinear integer programming model is constructed for bus hybrid dispatching strategy containing holding and stop-skipping.Also,the model can update the data real-time as the introduction of the adaptive decision.The model is able to capture the dynamic and uncertainty of various factors in transit system accurately and predictive the impact on the transit system as the implement of holding/stop-skipping strategy real-time.Lagrangian Relaxation is designed to sovle the problem and the optimal hybrid scheme can be obtained in real-time.Finally,using the bus GPS and bus IC data of Line 104 in Harbin,a case study is conducted.Based on bus travel time prediction and transit OD identification,the three transit in-station dispatching strategies are verified in practice.Results show that,under different situations,these strategies can reduce passenger average waiting time significantly and provide a better transit service.