Real-time Density Estimation on Freeways With Loop Detector and Probe Data

Density, speed and flow are the three critical parameters for traffic analysis. Traffic management and control with good performance requires the estimation/prediction of distance mean speed and density for large spatial and temporal coverage. Speed, including time mean speed and distance mean speed, and flow are relatively easy to be measured and estimated in the real-world applications, while less emphasis was put in measuring and estimating density. This paper summarized the methods for estimating density, mainly based on the loop detector data, proposed a method to estimate density with both the loop detector data and Vehicle Infrastructure Integration (VII) probe vehicle data. Better results were obtained from the proposed method, and Berkeley Highway Laboratory (BHL) loop detector data and the field collected Probe Vehicle data were used to verify the methodology.