Bus Operation Process Modeling And Adaptive Holding Control Strategy Analysis And Assessment Methods

The bus priority development strategy is an important measure to cope with the increasingly serious traffic congestion and pollution in major cities,improve the quality of life of the people,and promote sustainable urban development.In the urban public transport system,bus transit plays a major role with its flexible route layout and wide coverage.However,due to the complicated traffic environment and the low level of bus management and dispatching measures,the reliability and efficiency of bus operations are generally low,and the phenomenon of bus bunching and overloading frequently occurs,which significantly reduces the operational service level and the competitiveness and attractiveness of public transportation compared with other modes of transportation,and therefore restricts the sustained and rapid development of the priority development strategy of public transportation.With the development of public transportation intelligence and information technology in recent years,bus operators can monitor the operation status of the public transportation system and control bus vehicles’ operation in real time.Under this background,relevant scholars and practitioners have carried out extensive research and practice for the dynamic control of bus transit.A variety of bus dynamic control methods such as holding control,stopskipping control,and signal priority control are developed.Advanced control concepts like optimization-based control and feedback control are introduced into constructing and solving such control methods.This paper focuses on the adaptive holding control problem of bus transit,and make further studies on the following three aspects based on existing research.Firstly,based on the tree diagram matrix,a mathematical method for describing the bus operation process is constructed.This method can more deeply explain the intrinsic cause of the unreliability of the bus operation process,and more accurately describe phenomena like bus bunching and overloading.The second is to relax the constraints in most of the existing studies which require sufficient slack time to be inserted at control points.Instead,this paper proposes a quantitative analysis method to evaluate the influence of the combination of any environment and control parameters on the reliability of bus operation.The method can effectively balance the tradeoff between bus operation reliability and efficiency with the implementation of adaptive holding control strategy.The third is to further discuss how bus capacity limit impacts the evolution process of bus operation reliability.And a quantitative analysis method is developed to evaluate the implementation effect of adaptive holding control on passengers’ average ordinary wait time,average extra wait time and average in-vehicle travel time.This method can be used as an effective tool to solve the optimal holding control scheme.Specifically,the main research contents and results of the dissertation include:(1)An analysis method based on the tree diagram matrix is generated to analyze bus schedule deviation.The interference effects of various random factors encountered during buses’ operation is sorted out in the form of tree diagram matrix.The recursive iteration of the tree diagram matrix can well reveal the accumulation and amplification of the bus schedule deviation with the bus operation process,and also explain the operational correlation between buses from the theoretical level.The relevant analysis results well replicates the so called“faster buses go faster,slower buses go slower” and “bus bunching” phenomena.In addition,this paper finds that when buses bunch,the bunched buses will run in the form of bus fleets,and the operating rules of buses will change accordingly.To this end,a method is developed to dynamically correct the tree diagram matrix considering bus bunching phenomenon.The modified tree diagram matrix focuses on bus fleets rather than single buses as the research object to analyze the bus operation process.Results show that the modified tree diagram matrix is a good description of the evolution process of the bus schedule deviation after bus bunching phenomenon occurs.(2)Firstly,an adaptive holding control method based on equivalent control parameter is proposed without considering buses’ operational correlation and bus bunching phenomenon.This method relaxes the constraint which is held by most of the previous studies that a large enough slack time must be inserted into control points.Instead,this method manages to analyze the implementation effect of bus holding strategy by replacing the original control parameter with equivalent control parameter.Then,the bus holing process is further studied by using the tree diagram matrix with considering buses’ operational correlation and bus bunching phenomenon.By analyzing the holding process of the first vehicle,tail vehicle and the most intermediate vehicle in the bus fleet,a numerical method is generated to calculate the departure tree diagram matrix at control points.In addition,the analysis results show that when the slack time inserted at control point is small,the average holding time of bus fleets is the summation of the original slack time and an extra offset.(3)In actual bus operation,the available bus resources are often limited(such as limited bus fleet size,limited bus capacity,etc.),and it is necessary to adequately develop adaptive holding control schemes to fully utilize bus resources and achieve stable and efficient operation of the bus transit system.To this end,the analysis method of bus operation process considering limited bus capacity is proposed by using the tree diagram matrix.This method analyzes passengers’ boarding process at both control points and non-control points by using the bus fleet as the research object.After that,the paper analyzes the trade-off problem of the selection of holding control parameters when bus resources are limited,and proposes a method to evaluate the implementation effect of the adaptive holding control strategy from the perspective of bus passenger travel time.The proposed method can calculate passengers’ travel time cost such as average ordinary wait time,average extra wait and average in-vehicle travel time under any holding control scheme.