Optimization For Traiffc Signal Setting Considering The Influence Of Bottleneck In Urban Street Networks

Traffic signal control is an important means to regulate urban traffic flow, reduce congestion,and it also can ensure the operation of traffic flow normally and orderly. The traditional signalcontrol signal timing methods considers the optimization of dynamic traffic flow in urban streetnetwork. It can improve the safety of the intersection, the operation efficiency and fairness of thenetworks; and it also can promote the improvement of the level of urban traffic management inthe world observably. However, the traditional signal control system is mainly applied tounsaturation condition, without considering the interaction between the traffic streams upstreamand downstream. The literature is limited regarding methods of signal timing underoversaturation conditions. With traffic congestion continuing to grow in urban areas, a growingnumber of signalized intersections are operated under oversaturated condition frequently, and thequeue length of some roads even close to the link length during peak periods, which leads tospillovers. The role of spillovers in city street network is very significant, and it is already knownfor example that spillovers can lead to gridlock on ring roads and other network with closed loop.In order to prevent the occurrence of spillovers and reduce the spatial and temporal fluctuationsof the traffic congestion status, area-wide cooperation control should be implemented in urbanstreet networks; meanwhile, it is necessary to identify and dissipate spillovers accurate andtimely, so as to avoid the negative influence either in complex urban systems or at intersections.In order to adapt to the complex urban traffic situation recently, this paper takes the dynamicoptimization of the traffic signal timing in urban street networks as the core, considering theinfluence of bottleneck. The emphases of the paper include signal timing for an isolatedintersection with the influence of bottlenecks, area-wide cooperation compatibilization control,identification menthods of spillovers, and signal timing optimization for spillovers dissipation.According to the contents mentioned above, this paper will mainly discuss the following fiveparts.1. Optimization method of signal timing for isolated intersection sonsidering the operationalcharacteristics of traffic flow Firstly, the operating efficiency of non-priority traffic atunsignalized intersections and the average vehicular dealy at signalized intersection is analyzed,and the critical traffic volume for signal installation is determined from the veiwpoint of theoperation efficiency of the intersection. Then, signal control strategies under different trafficconditions are discussed, and the optimization idea that minimizing the number of vehicles in all approach lanes within the optimization horizon is proposed, taking the comprehensive efficiencyof all approaches lanes as the optimization objective. This research may provide a new theoryreference for determining the signal timing parameters especially when the intersection includesbottlenecks.(2) Signal timing for area-wide compatibilization with the influence of bottleneck. Theobjective of signal control under nearly saturated condition is analyzed firstly, and the controlstrategy and objective function are proposed. Based on the interaction of the upper and downtraffic flows, the calculation method of the number of vehicles in one special lane at thebeginning of one cycle is advanced with the influence of network topology. With the idea thatminimizing the number of vehicles in all approach lanes within the optimization horizon as theoptimizationobject, the optimization method of spilt for all signals is proposed consider therestriction of maximum and minimum green time. Combineing the rules of output and input forsections, the dynamic evolution process of optimization offset is described, which could supply abasis for coordination control under high saturation conditions.(3) Spillovers identificition in urban street networks based on upstream fixed traffic data thispart provides a calculation method for the occupancy per cycle under different traffic conditions,based on the relationship between the three basic traffic flow parameters, speed, traffic flow, anddensity; and then presents a method to identify spillovers in an urban street network based onupstream fixed detector data, using occupancy per cycle as the determination index; This partalso introduces traffic wave models modified by a kinematic equation, and determine thethreshold of occupancy, which characterizes the appearance of spillovers; The accuracy andusability of the new method are verified by VISSIM simulation, using the ratio of misjudgmentas the evaluation index. Finally, the precision stability of the spillover identification method isanalyzed(4) Spillovers identificition in urban street networks with the traffic data at bottleneck this partpresents a determination method of threshold for bottleneck state in urban street network basedon queue detector data, using ocupancy per cycle as the determination index. The threshold ofoccupancy for congested condition could be determined combining with the different effectivevehicle lengths. The data of rolling time occupancy under unsaturated and saturation states isobtained with VISSIM simulation, and a new array using the minimum of successive occupancyis achieved with different positive integers as the interval. Considering processing of vehiclespassing through the queue detertor as a production process, the rolling time occupancy could beregarded as the corresponding products, which obeys non-normal distribution; these dataproduced by the non-normal process could be transformated to normal ones by Johson curve family, and the upper bound with different interval was determined with the basic idea of qualitycontrol; contrast analysis the occupancy threshold and the upper (lower) bounds with differentinterval, the trigger and termination conditions for bottleneck control are deceided.(5) signal timing optimization for spillovers dissipation bottleneck control strategy andcontrol manner is analyzed firstly, and the signal timing optimization methods for spilloversdissipation are proposed based on the results of part3and4; meawhile, smooth transition meansbetween bottleneck and conventional control projects is provided, and the two methods areevaluated by VISSIM simulation.In the last, the main progress and achievement of this dissertation are summarized, andthecontents and problems which need to perfect and explore further more in the study areputforward.