The Calculation Of Signal Timing Parameters Based On The Traffic State Identification Of Critical Intersections

Since the ninetieth of twenty century, euro countries bring forward a whole new traffic model—ITS, which improves traffic condition a lot. as the most important part of ITS, ATCS (advanced traffic signal control system) is not only important traffic information collection sub-system but also core operation sub-system that coordinates traffic flow distribution, that is: sub-system which adopts signal control on intersection, pedestrian and ring road, it is the application system that combines traffic engineering, psychology, application mathematics, automatic control, information network technology and systems engineering.In the western developed countries, Traffic control system theory develops from fixed timing signal control system, traffic-actuated control system and self-adaptive signal timing control system, which spans for several decades. While it only starts in china since traffic signal control system is concluded in the national "QiWu" keystone scientific projects. Though our country marketed several traffic control system since 1990, maturity and practicability of these products is way worse than the counterparts of products made by western countries. While the essay does some researches on traffic control system based on actual traffic condition in china.Taking the key technology research of next generation intelligence traffic control system" (project serial number: 2006AA11Z228) of 863 national projects and "research on the mixed traffic control system and traffic flow induction system cooperation operational mechanism and method" (project serial number: 20040183035) of college doctor station fund projects as the research platform, The essay did some researches on traffic signal control system.In order to coordinate traffic condition in cities better, the essay brings forward the real time estimation of critical intersection of traffic control area to choose the control strategies of different control area and at the same time, it provides different calculation methods under the different traffic condition of critical intersection, different roads, and different intersections.First chapter: introduction. This chapter brings forward the research background of the essay. That is: point out that as a important part of ITS, the theoretical meaning and practical value of research on traffic control system. I fix on the research content and essay structure based on this.Second chapter: the framework and principle of traffic signal control system and layout designing of traffic detectors. This chapter does some deep research on the system structure, control goal and timing optimization of SCATS and SCOOT self-adaptive traffic signal control system. By comparison and practical application effect on some cities, the essay bring forward the basic structure and framework of self-adaptive traffic control system. The system adopts the three-layer distributive control structure to adjust to the demand of distribution optimized control system, including line controller, area controller and intersection controller. . At last the chapter analyses the object of data collection of critical intersections and special layout principle of critical intersections, and brings forward the actual layout method of traffic detectors in critical intersections combining the layout principles of vehicle detectors, based on which the essay calculates the basic traffic parameters (traffic density, speed and traffic volume).The third chapter: The traffic condition and evaluation index of operational efficiency of critical intersections. At first, the essay analyses the calculate methods of basic parameters of traffic detector (traffic flow, speed, occupancy ratio, and traffic density). At the same time, the essay analyses these parameters (traffic capacity, saturation, delay, parking ratio and queuing length).Combining the layout of critical intersection traffic detector, the essay improves on the queuing length calculation model, which is good for evaluating queuing length, and at last, It validates the model on the approaches of critical intersections with the VISSIM. By comparing with traditional method, the essay undertakes the real time evaluation of traffic condition of critical intersection using the "mode identifying method" of fuzzy mathematics as the principle of choosing the operational strategies of control system. According to three different traffic conditions of critical intersection, the essay does some deep research on the control strategies that the system should take.The fourth chapter: area timing parameter calculation and analysis on control strategies based on the traffic condition of critical intersection. At first, the chapter divides the traffic condition of critical intersection into three different traffic conditions: free, slightly crowded and severely crowded. In the end of this chapter is the timing optimization study under the given control strategies. Under the free traffic condition, the essay chooses performance index of traffic delay and parking ratio to optimize the signal timing parameters. Under the slightly crowded traffic condition, the control system chooses performance index of traffic delay, parking ratio and congestion level to optimize the signal timing parameters. Under the serious crowded traffic condition, the control system solves the congestion problem of critical intersection. In the end of the chapter, the essay does some research on the optimization of signal timing parameters. Under the free and slightly crowed traffic condition, the essay undertakes the frequent, small-pace, self-adaptive adjustment method to optimize the signal timing parameters. Under the severely crowded traffic condition, the control system uses the improved green ratio model according to the control strategies combination of different conditions to calculate the signal timing parameters. And validate the model with VISSIM, it turns out that this method can shorten the lasting time of traffic congestion and decrease the queuing length near the intersection.Final chapter: overall summary and expectation. This chapter summarizes all the content of this essay, looks back on the main content of essay, at the same time, points out creative content and shortcoming of essay, and the task that needs to be done in the future.