Research on the Macroscopic Fundamental Diagram for Shanghai urban expressway network

摘要

This paper are trying to investigate the existence and the characteristics of macroscopic fundamental diagram (MFD) for urban expressway network in different types of days based on detectors data in Shanghai, China. At first, the features of the urban expressway is discussed relating the speed and occupancy, and then the existence of MFD in Shanghai urban expressway network is proved based on one week’s data. Moreover, the hysteresis phenomena exist in most days and the network exhibits different hysteresis loops under different traffic situation. In order to explore the reason of hysteresis loops, all the detectors are categorized into seven types. When the free flow detectors are removed, the hysteresis loop also exist like the MFD of all the detectors. And when those detectors whose flow-occupancy relations exhibit similar hysteresis loop are removed, the hysteresis loop of MFD is not clear. Hence, they are proved to be the important part of all the detectors. And the hysteresis loop of individual detectors are influenced by shock waves and traffic situations. And the transitions of free flow traffic to congested traffic and the transitions of other way around are different. Hence, the fundamental diagram of individual detectors has significantly impact on the hysteresis phenomena of MFD. It is worthwhile to study the key detectors when the hysteresis of the MFD are discussed.