Study On Models Of Delay And Queue Length At Saturated Intersections

Delay and queue length are measures that can compare theperformance of an intersection under different control, demand andoperating conditions. The accurate prediction of delay is therefore, animportant measure of effectiveness. However, accurate estimation of delayis difficult due to random traffic flow and other uncontrollable factors at theintersections. The study of this dissertation is supported by the NationalNatural Science Fund Project "Study on the Critical theory and simulation ofUrban network dynamic traffic manage and control", and study on delay andqueue length models.The primary objective of this dissertation is to develop delay and queuelength models of intersections, pay more attention on attaining timedependent delay and queue length models at the over saturated conditionsexactly, and optimization of signal planning using these indexes. Thedissertation starts with cumulative curve, emphases arrival models ofdownstream intersections in virtue of signal timing parameters of theintersections upstream, which father effect the value of delay and queuelength. The way considering effect of upstream intersections makes effectevaluation indexes connect with offset optimization in the traffic networkcontrol system close. The dissertation consists of six chapters.The first chapter introduces state of problem and the researchobjectives of this dissertation. Urban traffic control effect evaluation is theprimary part of urban traffic control system, and used in the systemoptimization and system evaluation. Delay and queue length are the mostimportant indexes of traffic control system control effect. So this dissertationstudies the important part of traffic control effect evaluation theory——thedelay and queue length models at signal intersections.Chapter 2 primarily provides an extensive review and a theoreticalbackground of delay and queue length theory and some traffic flow theoryused in this dissertation. Traffic engineers abroad already at lengthdescribed uniform, random and continues overflow theory, which werereceived by most researchers. Now how to consolidate the steady anddeterministic theory are primary aspects of study on traffic control effectevaluation. However, most theories are basis on the uniform arrival, which isa flaw of these theories in practice. Domestically, a lot of research institutesand researchers also dedicate to develop some traffic control systemssuiting for our country. But as a result of lack of experience, they onlydirectly use foreign fruit;this makes value of theory different to reality. Trafficflow theory present probability theory that describes platoon dispersion,including continues distribution and dispersed distribution and traffic wavetheory that often is a method to determine queue length according to thedifference of traffic density and flow rate resulting traffic wave speed.Chapter 3 studies determining methods of arrival flow characteristics.Firstly it fits arrival distribution and cumulative flow data and gives its formulaand applied condition, the result shows cumulative fit curve is superior todistribution fit curve arrival;then predicts pattern of downstream byanalyzing real-time upload flow data and platoon dispersion, and validatesplatoon dispersion, gets the result that Normal and Roberson distributionsapproach the reality and are practical and gives its applied condition. Asthose methods doesn't consider traffic signal timing influence on arrivalcharacteristic. This chapter fit traffic release characteristic is that vehiclesrelease with uniform at green period and Poisson at red period. This releasecharacteristic basis on upstream signal timing could connect traffic flow oftwo intersections well, which is convenient for coordinated control.Chapter 4 develops delay and queue length basis on vehicle arrivalcumulative curve and describes the improvement to signal timingoptimization aiming at over-saturated condition. Existing theories alwaysassume vehicle arrival is uniform which is different from true, so thisdissertation develop delay and queue length basis on vehicle arrivalcharacteristics. Moreover, in the queue length model, this chapter studiesplatoon dispersion effected by the intersection that describe the vehicleprocess from dispersed to impressed state. Last part brings forward signaltiming optimization aiming at over saturated condition. It proceeds withsettling the saturated condition, provide two ways which is to control trafficdemand and increase traffic supply. And it uses area control to settle anintersection of several saturated states with adjacent intersections.Chapter 5 takes the example of the intersection of GongNong square,that is an intersection with five approaches. This chapter verifies theoreticalmodels of delay and queue length, the result indicates the theoreticaloutcome is approximate to real, sometime superior to deterministic theorywhich approves the accuracy of theoretical models. There is over-saturatedin the approaches of east NanHu road, so this chapter develops signaltiming project of intersection. Comparing exist signal timing and Webstertiming theory, the result shows this improved project that is superior toWebster timing theory, could largely reduce average delay and keepcapacity steady.In the sixth chapter, the author sums up the dissertation, looks back allthe course and development of the research and enumerates all theproblems that need to be further studied.