Research on Spatial-Temporal Features of Urban Freeway Congestion

Relieving traffic congestion on roadways has always been one of the priority concerns of traffic engineers. Thoroughly understanding the factors which cause traffic jams plays the fundamental role in planning, design, construction, and management of roadway facilities. This paper focuses on experimental observations and theoretical analysis of urban freeway congestion due to complex features of traffic flow, shock wave and state transition. Real time dejected data were collected to calculate shock wave speed and establish vehicle trajectory models. A typical urban freeway segment in the center of Shanghai City is used in this analysis. As a result, conclusions have been drawn and the theory of shock wave speed could be used to help establishing traffic control strategies and to control queue length.