Study On Road Congestion State Assessment And Macroscopic Fundamental Diagrams Based On Floating Car Data

With the rapid development of economy, the traffic congestion phenomenon is more and more common in city. However the traffic congestion problem not only affects the normal travel of people and the management of urban environment, but also restricts the development of urban economy. Therefore, how to quickly identify the traffic congestion and take effective solutions in time is an important research topic in the field of contemporary ITS.In recent years, with the development and wide application of various types of capture technology, ITS is entering the era of big data. Compared with the fixed detectors technology, floating car devices have many advantages, such as easy install and maintenance, high accuracy for the uploading data, etc. For these reasons, the data collection technology based on the floating car has become the important source of urban traffic state data analysis.In this work, the data of floating cars in Beijing are utilized. Based on these data, this paper research on the estimation of the maximum queue length of intersection and the evaluation of the traffic running state in study area. On this basis, the analysis of the MFD (Macroscopic Fundamental Diagrams) can be estimated.Firstly, the data is pre-processed by using the methods of data pretreatment. Then, the estimation of the maximum queue length is giving by the distribution situation of the low-speed floating car data points (instantaneous speed is less than 5km/h) in the intersection. Meanwhile, a queue length correction algorithm is proposed, which utilizes the information about the number of floating car in the intersection import link, the import direction of the links and the number of links.Next, the maximum queue length of the link, the link speed and the link travel delay time are defined as area congestion state evaluation parameters. Fuzzy comprehensive evaluation algorithm, gives a degree evaluation results of links and area congestion in different time periods.Finally, the proportionality coefficients between the total number of running cars and floating cars are calculated by the maximum queue length proposed in chapter 3. Furthermore, the relationship between the total number and the running speed of cars in study area can be obtained, as well as the relationship between average speed, average density and average flow in weekday. As a result, this paper analysis the existence of MFD in practical road net.