Research On Signal Control Methods Of Traffic Bottlenecks In City Road Network

Traffic congestion in china has been increasing is an indisputable fact, and along with urban economic development and the city size enlarge, urban traffic congestion's degree continues to deepen and the scope continues to growing. It can be said that, due to various constraints, a certain degree of traffic congestion in peak hours in the urban road network is inevitable. In these circumstances traffic managers need to consider how to reduce traffic congestion, restricted the scope of overcrowding. In essence, congestion occurs as a result of traffic imbalance between demand and supply, which had occurred first in the road network's bottlenecks during the peak travel period. When the traffic demand reaches a certain extent, the traffic bottleneck will form a long queue of vehicles, and induce a small scope of the traffic jam. This local network congestion have little effect on the whole network's traffic operation, but if we do not take timely measures to control the queue when the vehicles traced to the upper intersection, it may affect the flows'normal operation in upper intersection, which led to road network traffic flow locked, causing large traffic jams or road network traffic gridlock.The above traffic jams chain similar to the phenomenon of the proliferation of "Domino" domino collapse of the chain reaction, also known as traffic "domino" phenomenon. Traffic "Domino" is the phenomenon of urban traffic congestion extreme manifestations, its consequences and impact is the most serious. Therefore, traffic control measures must be taken to prevent the emergence of such a phenomenon. The degree thesis research is searches for how to make use of traffic signal control means to prevent city traffic "domino", and bottleneck control strategy is presented as a result. Bottleneck control strategy is a traffic congestion control strategy, for a single isolated intersection control and coordination of a number of intersections control, the paper proposed single point bottleneck control strategy and coordination bottleneck control strategy, they were bottleneck control's applications in a single point of control and the coordinated control mode. Papers designed bottleneck control methods, including detector emplaced, control strategy conversion conditions and control model algorithm. Papers consider its effective application to the actual traffic control when design the bottleneck control strategy, and therefore consider the practical ability to obtain information and traffic control model algorithm can be realized, guarantee bottleneck control strategy has both theoretical and practical application significance.Mostly signal control intersection in China used single-point control, and single point control is the basis of the coordination control, there for papers initially research on the single point bottleneck control strategy. Traditional signal timing theory supposes that the queue of vehicles is at the parking line, which means that the traditional signal timing theoretical assumptions queuing vehicles unable traced to the upper intersection. When the intersection saturation in the lower section and the road is long, the above assumption can be considered correct. But when the intersection lasted too saturated, it is prone to accumulate the vehicles extended to the upper intersection. Then the basis of the traditional signal timing theory has not exist anymore, so its timing result is bound to be unreasonable.To resolve these issues, this paper presents a single point of bottleneck control strategy. Single Point bottleneck control strategy includes three main parts: detector settings, control strategy conversion conditions and single-point signal timing algorithm. Control Strategy Implementation detection devices need to support the provision of transport information, in accordance with the requirements of the bottleneck control algorithm, the paper design of the sensor detector and trigger detector. Detector sensors for real-time detection traffic flow, triggering detector used to determine traffic conditions. Papers presented detailed induction detector and trigger detector the size and location of deployment. In the intersection of unsaturated using ordinary control strategy, and bottleneck control strategy is used once the intersection lasted too saturated and may lead to "domino" effect. According to the state take the corresponding traffic control strategy is essential, therefore reference the layout position of trigger detector, paper given the control strategy shift conditions. Timing algorithm is the core of bottleneck control, the intersection used bottleneck control must be saturated, therefore the largest cycle is selected as operation cycle to greater traffic capacity. In order to fully utilize the space resource of the intersection imports to prevent queuing traced, this paper presents a "equate queue intensity" model. Queue intensity is the ratio of the queue length and import length, the greater the queue intensity the queuing more likely to be traced. The "equate queue intensity" model can balance the queuing pressure of each imports, and ensure maximum use the intersection's space resources to prevent the "domino" phenomenon.In order to use the related intersection sharing the bottleneck's traffic pressure, the paper proposed a coordination bottleneck control strategy. Coordination bottleneck control strategy includes detector emplaced, control strategy conversion conditions and coordinate signal timing algorithm, and its laid detector and the control strategy converted conditions can reference to a single point bottleneck control strategy. This paper designed two coordination bottleneck control algorithm, which are the balanced pressure method and the regulation of small steps method. Balanced pressure method's basic idea is to transfer the traffic bottleneck's pressure to the upper intersection, balanced the traffic pressure in the region. The small step method regulating small step away from the intersection of regulation and control bottlenecks associated connection phase green time, and gradually ease the bottleneck intersection congestion problems. Connection control the selection of the principle can guarantee the effectiveness of regulating traffic demand, directly increase the green light time bottleneck phase supply regulation can ensure the effectiveness of traffic supply. From a practical application point of view, the small step method is conducive to maintaining the stability of control system, reducing reliance on the test information, and error detection information is the important reasons of poor control effect. Papers on the bottleneck control strategy demonstration and simulation test results showed that compared with normal control strategy, the bottleneck control strategy is more conducive to prevent "domino" phenomenon occurred and it reached the bottleneck control purposes. In order to prevent large-scale traffic jams, this paper advanced a single bottleneck point control and coordination bottleneck control strategy, and this paper's research mainly including detector emplaced, control strategy conversion conditions and signal timing model three parts. The research does not only improve the city's traffic congestion control theory, but also can be used in engineering projects and has the economy value.