Estimating Network Fundamental Diagram using Three-Dimensional Vehicle Trajectories: Extending Edie’s Definitions of Traffic Flow Variables to Networks

摘要

This paper evaluates different measurement methods of traffic flow variables taken at the network level. Generalized Edie’s definitions of fundamental traffic flow variables along highways are extended to consider vehicles traveling in networks. These definitions are used to characterize traffic flow in networks, and form the basis for estimating relations amongst network density, flow and speed, in the form of a Network Fundamental Diagram (NFD). The method relies on three-dimensional vehicle15 trajectories to provide estimates of network flow, density, and speed. Such trajectories may be routinely obtained from particle-based microscopic and mesoscopic simulation models, and increasingly becoming available from tracking devices on board vehicles. Numerical results from the simulation of two actual networks, Chicago and Salt Lake City, are presented to illustrate and validate the estimation methodology. As part of the verification process, the study confirms that, as expected, the traffic flow fundamental identity (Q=K.V) holds at the network level only when network-wide traffic flow variables are defined consistently with Edie’s definitions.