The Relationship of Speed-Flow-Density for the Mix Traffic Flow on Beijing Urban Expressway

According to the intra-vehicle interaction, a generalized speed-flow relationship of highway consists of three regime including an congested part, a queue discharge and within the queue. Different from the highway speed-flow-density relationship, the urban expressway has more complicate characteristics. Based on one month serial data collected from loop detectors on different sites of the expressway in Beijing, we find the relationship of speed flow and density changes remarkably during different period of time. So a more appropriate way to explore speed-flow-density relationship is to research it under different period of time. This paper will establish a speed-flow-density model during nighttime and daytime separately, and analyze the key point of K-V, K-Q and Q-V curves.