Qualitative analysis of traffic jam formation in urban ring road

In this paper, the procedure of traffic jams formation in urban ring road are studied qualitatively. Some concepts such as homogeneous measure index (HMI) and spatial-temporal difference index (SDI) are utilized to scale the cross-lane inhomogeneities of the traffic flow, and the spatial-temporal state transitions of the traffic flow are explained in terms of HMI and SDI. We present the actual data of Beijing Third Ring Road to describe the procedure of a traffic jam formation, and the concepts proposed in this paper are used to explain the causality of the traffic jam formation.