AN AUTOMATIC CALCULATION METHOD OF IDENTIFYING THE HYSTERESIS LOOP CHARACTERISTICS IN MACROSCOPIC FUNDAMENTAL DIAGRAM

摘要

Recent studies showed that hysteresis phenomena are exhibited in macroscopic fundamental diagram (MFD) in urban freeway networks. This paper proposes an automatic calculation method of identifying MFD hysteresis loop characteristics and apply it to explore the characteristics of the hysteresis loops and the factors affecting the hysteresis pattern. Compared to the traditional observation method, this automatic calculation method extracts key characteristics of hysteresis loop directly from the network flow-density data. This method improves the efficiency to characterize hysteresis loop by identifying the direction of hysteresis loop, starting point and ending point of the hysteresis loop, and the maximum average network flow. To test this automatic calculation method, the macroscopic fundamental diagram for urban freeway network in Milwaukee is presented in this study. Key characteristics of hysteresis loop are extracted by the automatic calculation method and calculation results are validated by empirical observation data.