Design And Research Of Signal Control System Based On Real-time Traffic Flow Information

Recent years, with the development of the urbanization process in our country, the number of deferent kinds of motor vehicles has been growing sharply so that the intersections are under great pressure. It takes vehicles much waiting time to pass the intersections under the traditional fixed-time signal control scheme so that vehicles will produce large amounts of carbon dioxide emissions, which makes a great threat to the ecological environment. Thus, a rational intelligent traffic control scheme is practically significant to improve the urban road traffic conditions and the ecological environmental quality. Based on real-time traffic flow information, a speed control scheme for vehicles and traffic signal control scheme for single intersections were studied in this thesis, aiming at reducing carbon dioxide emissions produced by vehicles when passing the intersections.Firstly, this thesis summarizes the development of traffic control methods and analyzes the advantages and disadvantages on several classical typical road traffic control systems. As the information acquisition of traffic flow is the basis and prerequisite of the traffic control, this thesis introduced some mature of vehicle information detection technologies. Moreover, this thesis makes a description of intersections in mathematical terms and a discussion on the basic concept of traffic control as well as the optimization decision methods.Secondly, this thesis proposes a control system comprised of a speed control module and a signal control module for single intersections. In the speed control module, information about vehicle's speed and position is sent to the control center by V2V and V2R communication, drivers can receive a recommended speed according to the current traffic signal phase and the remaining time so that vehicles under VANETs environment can cross through the intersections in a most smooth movement even when the vision is not enough. In the signal control module, with the help of the application of adaptive cruise control, controlled object changes from the discrete vehicle to the platoon flow that the distance between vehicles can be measured, when the head vehicle approaches the detecting area of intersections, the state information of other vehicles in the platoon will be transferred from the last to the first by multi-hop communication along the driving direction. According to the real-time traffic flow information and the basic principle of first in first out, the control center will generate the signal-changing policy so that it can reduce vehicles' waiting time as much as possible. The simulation results conducted by MATLAB indicate that the proposed scheme does help to reduce carbon dioxide emissions for vehicles approaching intersection when compared to the fixed-time scheme.Finally, integrating with the actual case, this thesis analyzes the shortcomings of traditional fixed-time scheme by VISSIM simulation and combines the bus priority signal control strategy with the proposed scheme, a two level scheduling scheme based on bus rapid transit priority is also proposed. According to the simulation results conducted by MATLAB, this scheme can still sharply reduce waiting time and carbon dioxide emissions for common vehicles approaching the intersections.