Research On Key Technologies Of Expressway Safety Early-warning System Based On Traffic Flow Theory

With the rapid development of our national economy, traffic problems are becoming more and more serious. Intelligent Transportation Systems (ITS) perhaps are effective ways to solve or alleviate various traffic problems. The main functions of expressway traffic safety early-warning system are to provide corresponding control strategy and prevent the happening of accidents, by the traffic conditions and meteorological conditions, traffic flow characteristics, and so on.The main contents in this paper includes 6 chapters: 1, introduction; 2, the structure design of expressway traffic safety early-warning system; 3, expressway traffic information collection and management technology; 4, the correlation analysis between expressway traffic flow main parameters characteristics and traffic safety; 5, the study of traffic state identification algorithm based on the theory of traffic flow compressibility; 6, summary and outlook. Specific research concentrates are on the following:(1)The paper defines the expressway traffic safety early-warning system's main function. The expressway early-warning management has four basic functions: warning, correction, emergency disposal and immunity. Expressway early-warning management can provide the development trend of expressway traffic safety process description based on the judgment of the development status of traffic accident. The system will judge the expressway traffic flow characteristics,and report to the traffic management department in time when it had bad changes, then adopts corresponding counseling measures, so plays an important effect for serious accidents (especially super-large traffic accidents and secondary accidents).(2)The paper analyzes the information demand of expressway traffic safety early-warning system. The users can be divided into three categories: the administrator of expressway, the person who participate expressway, and the server of expressway. The primary responsibility of the managers is to use various resources and means to ensure the expressway safety operation by macroscopically and microcosmic management. Therefore, they need much traffic information to improve the level of management and service. The users of the expressway can know the safety information by various information release means, and avoid the traffic accident according to traffic misleading information. The server can obtain the expressway traffic safety information by checking system data, then make service strategy and formulate more targeted service for effective operation.(3)The paper provides a structure framework of the expressway traffic safety early-warning system. According to the functions, the system can be divided into three subsystems: basic transportation information acquisition subsystem, early-warning information processing system, and information release subsystem. It can fuse all sorts of multi-source data of original traffic heterogeneous come from all kinds of traffic information collection equipments, then identify the traffic condition and send out warning information according to the predetermined algorithm.(4)The expressway traffic information acquisition and data management techniques are discussed. In this part, the paper mainly discusses the dynamic and static information collection mode. Firstly,expressway traffic information pretreatment technology is discussed, and then the paper introduces the abnormal traffic data and incomplete traffic data processing method. It introduces the function of data fusion firstly, and then discusses the expressway spatial average speed and fusion algorithm of traffic flow. Based on the data needs, it designs the concept of the data warehouse structure, logic structure, physical structure, and puts forward the design of the data storage solutions and data storage system structure. Finally, it analyzes the implementation method of data warehouse, and discusses the data quality management and integration method.(5)Based on the measured data of three expressways such as chang-ping, the author discusses the correlation relationship of traffic flow and traffic safety. The research starts respectively from the characteristics of the number of vehicles, the speed traffic flow, traffic flow structure, and then summaries their rules. The result provides a theory basis for the establishment of traffic safety early-warning system.(6)The author builds a kind of traffic state identification algorithm. Aiming at the bad state, it can be issued three kinds of warning or alert. The algorithm is especially strengthened for routine monitoring of operation condition of traffic flow. Combining with the traffic flow compression theory, it provides the traffic flow compressibility and density of traffic flow relationship model (see 5.22 ), traffic wave and traffic flow density relationship model (see 5.23 ), traffic wave and traffic flow density actual occlusion relationship model (see 5.24 ). Through 2 examples, the algorithm calculated is applied. Finally, it demonstrates the effectiveness of the proposed algorithm.The research contents, methods and conclusions involved in the paper can provide certain theoretical basis and engineering technology reference for related system.