Methodology for Calibration of Fundamental Diagram based on Trajectories of Sampled Vehicles: Concept and Numerical Experiment

Abstract

A fundamental diagram (FD), also known as flow–density relation, is one of the most important concepts in traffic flow theory. It would be valuable if an FD could be estimated by GPS-equipped probe vehicles;because they can collect data from wide spatiotemporal area, compared to traditional fixed sensors. This paper proposes methodology for estimating an FD based on trajectories of sampled vehicles. The proposed methodology estimates values of a free-flow speed and a critical density of a triangular FD, while it exogenously assumes FD's functional form and a value of its jam density. In order to validate the proposed methodology, an algorithm for estimating FD parameters is developed. The algorithm is based on the proposed methodology and is designed to heuristically estimate FD parameters from actual traffic data. Then the algorithm was validated based on traffic data generated by microscopic traffic simulation. The results suggested that the proposed methodology can estimate FD parameters fairly accurately and robustly.