Research On Offset Optimization About Signalized Coordinated Intersections

Transportation came from the social production and living activities, greatlyrelated to human behavior. With the invention and development of automobiles,great changes occurred within transportation system, which heavily propelledhuman progress. In modern society, the increased use of automobiles becomes aheadache for the consequent traffic congestion, accidents and environmentpollution. Advanced city traffic control system is a key path leading to raised urbantraffic efficiency, and is a symbol for city modernization.The paper researched on the optimization of signal offset, the key technique intraffic control. Focus was on optimization aim, model and methodology from twoaspects: arterial coordinated control and area-wide coordinated control. The formeraimed at maximum green wave, while the latter at minimum vehicle delay. Theresearch is composed of interrelated chapters as follows:As economy develops rapidly in China, automobiles come into people's dailylife. Therefore, traffic problems are generated and become increasingly serious.In Chapter One, research background, significance and content were depicted.Maximum green wave band and minimum vehicle delay are the aims of offsetoptimization. Time-space method and mathematical analysis method are mostcommonly used in arterial coordinated control. In Chapter Two, work flow of thetwo methods was analyzed in detail. In the light, the simplified mathematicalanalysis method was applicable in: (1) calculating green wave width regardless ofthe balance of traffic volumes in opposite directions; (2) optimizing green wavewidth at double-cycle intersections in coordinated sub-area; (3) identifyingbottleneck intersections; (4) solving equations of green wave width, and so on.Volume forecast model was established to optimize the offset of different trafficvolume ratio in coordinated directions. Field data were used to verify the model,which indicated that the model would be simple and applicable in field work. It isworth mentioning that the recalibrated method has been applied in trafficsimulation software developed by the work team. With respective merits, hill-climbing method, combination method andmaximum green wave method are commonly used in area-control of offsetoptimization methods. In Chapter Three, the organism of combination method wasexplored to clarify its weakness. Vehicle flow was considered as even arrival, notrandom arrival. And intersection delay was only caused by the offset at the twointersections, not related to signaling at other intersections in the network. Thisweakness of the method was fully considered in the paper. In light of G. M. Pacey'stheory, intersection vehicle delay model was established by counting the arrivingand leaving vehicle flows, and considering whether the queuing vehicles maycompletely go through the green phase. Based on the combination and vehiclesflow pattern graphs, relation between offset and delay was confirmed. Microcosmic traffic simulation software is used to simulate various trafficsituations, and to put out control effects. Simulation software plays important rolesin application to intersection design, traffic control plan and information collection.Among software for traffic simulation, VISSIM, developed by Germany, is ideal insimulating unsignalized intersections, signalized intersections, and interchange design.Real situations on the roads are truly reflected. In Chapter Four, based on differentaspects of time period and flow ratio, arterial coordinated control plans weresimulated. Vehicle delay time as indicator, the result indicated that arterialcoordinated control plans were obviously superior to isolated signal control at peakhours. The paper took Xinmin Square, a five-leg roundabout as example. Networktraffic flow theory was used to analyze the reasons for congestion at rush hours. Onthe basis of traffic investigation, and theory of signal coordinated control, thedesign of actualizing sub-area coordinated control was proposed on the fiveupstream signal intersections at Xinmin Square. Through optimizing timingparameters at the upstream intersections and adjusting the offsets which control...