Characteristics of Macroscopic Fundamental Diagram for Beijing Urban Ring Freeways

A macroscopic fundamental diagram(MFD)gives an invariant functional relationship among macroscopic variables in a large urban area. Beijing as one of the largest cities in the world has a number of unique traffic features. A MFD is presented for Beijing urban ring freeways by using traffic detector data. It shows the characteristics of a MFD pertaining to Beijing urban ring freeways, and provides insight into traffic conditions in Beijing. A pattern that lower occupancy variance is associated with lower network flow is observed; it is different from present findings. The observation is investigated and is further attributed to outsync of 5th ring and a radial spread of congestion in Beijing.