Analysis of Traffic Speed-Density Regression Models -A Case Study of Two Roadway Traffic Flows in China

Speed, flow and volume are the most important elements of the traffic flow. In this study, the speed-density regression models are compared between congested city road and the tolled highway based on traffic flow data on Beijing Third Ring Road (BTRR) and Jing Jin Tang Highway (JJTH) in China, which are collected by road detectors on each road. The speed-density regression curves are analyzed based on four the classical models: Greenshields, Greenberg, Underwood, and Bell-shape models. From data analysis, it can be seen that Greenberg and Underwood models for BTRR and JJTH are presented with higher confidence and less variation. Through the comparison of the two roads’ regression models, it can be found that the free flow speed and the speed maximum flow level on highway is much higher than city road, but the density at maximum flow level and the jam density on highway is smaller than city road.