Research On Coordinated Control Methods In Urban Signalized Intersections

With the rapid development of Chinese economy, the acceleration of urbanization, and the improvement of motorization, the urban traffic problem has been the bottleneck to the sustainable development of economy and society to some extent. The Advanced Urban Traffic Control System is one of the important approaches to improving the operating efficiency in urban traffic. This dissertation chooses the key problem in urban traffic signal control—signal timing parameters optimization—as its research target. The study puts emphasis on the objectives, models and methods of optimization. The research findings of the dissertation contribute to a further study into the urban traffic control system, which fits the real traffic situation in China. It maintains high value and guidance function in scientific research. This dissertation consists of the following chapters interrelated with each other:1) A study on division method of Traffic Control Sub-Area. This chapter first brings in the preliminary definitions used in traffic signal control sub-area. And cycle index, distance index and volume index are discussed. The above-mentioned points are the basis of the dissertation, as the basic theory of signal timing parameter optimization.2) Coordinated control methods in signalized arterials. This chapter begins from the three basic control parameters, studys coordinated control methods based on the green wave. This section consists of three parts: (1) The optimization methods of cycle length. Cycle length is directly related to capacity and vehicle average delays at intersections. It is a very important parameter determining the traffic signal control benefit. The paper in-depth analyzes the existing problems of previously established traffic intensity model, modifies traffic - speed model and establishes traffic intensity model based on volume and time occupancy. Takes minimum cycle,maximum cycle and these average as base, uses growth curve to fit relation traffic intensity with cycle time model. The cycle length optimization model is proposed for intersections with 2～5 critical phases based on traffic intension. This method can uniquely confirm the state of traffic flow, and remedy the defects in conventional methods. (2) The optimization methods of split. Split reflects the length of green time of each phase at intersection. The optimization of split is to reasonably distribute effective green time to various phases. In this chapter, split optimization method based on actuated control is provides, which can enhance greenwave-band in main roads and decrease delays in minor roads.(3) The optimization methods of offset. Offset is an important timing parameter in traffic coordinated control, which directly determines the coordinated effect. In this chapter, the advantages and disadvantages of some methods are analyzed, including time-space method, mathematics analysis method and maxband method Then the mathematics analysis method has been improved. The enhanced mathematics analysis method can calculate the green wave width whether the traffic volumes of two opposite directions are imbalance, or there are double-cycle intersections in coordinated sub-area. It also can find the intersections which affect the green wave width, and obtain the linear equation group of green wave.3) Coordinated control methods for area traffic control. The chapter analyzes classic area traffic control methods,derives offset-delays model in two phase intersections, provides offset optimization method that makes a complex road network change many simple road networks. At last, the chapter explains the importance of timing plan transition, provides timing plan transition arithmetics in all kinds of traffic conditions.4) Especial case solution methods. This section includes two parts: (1) Coordinated Control Method of Roundabouts. The paper gives Xinmin Square, a five-leg roundabout as example. Network traffic flow theory is used to analyze the reasons for congestion at rush hours. On the basis of traffic investigation and theory of signal coordinated control, the design of actualizing sub-area coordinated control is proposed on the five upstream signal intersections at Xinmin Square. Through optimizing timing parameters at the upstream intersections and adjusting the offsets which control arriving flows in Xinmin Square,"signals"are installed in the front of the stop lines at the roundabout. By making use of the"vertical"signals, vehicle flow entering into the roundabout is separated by time. As a result, vehicle delay decreases. Consequently, street landscape is preserved, and vehicle flow situation can be enhanced at the roundabout. (2) Bottleneck control methods. Bottleneck control is an adaptive control method aimed at vehicle queuing, which balance approachs queue intensity, and prevents domino from occuring. In order to make the aim come true, the paper designs detector lay plan, establishes bottleneck control algorithms which consist in maximum cycle, split and offset optimization methods in saturation.In the end, the dissertation summarizes the findings and achievements, and brings forward the issues for further research.