The University of Massachusetts Amherst
University of Massachusetts Amherst

Search Google Appliance


Stochastic modeling of the equilibrium speed–density relationship

TitleStochastic modeling of the equilibrium speed–density relationship
Publication TypeJournal Article
Year of Publication2013
AuthorsWang H, Ni D, Chen Q-Y, Li J
JournalJournal of Advanced Transportation
Issue1, Special Issue: Traffic Control and Management—Recent Methodological Advances
Start Page126
Date Published01/2013
Keywordsfundamental diagram, Karhunen-Loe`ve expansion, stochastic speed–density model

As the graphical and mathematical representation of relationships among traffic flow, speed, and density, the fundamental diagram has been the foundation of traffic flow theory and transportation engineering. Underlying the fundamental diagram is the speed–density relationship which was originally documented in Greenshields' seminal work and followed by a variety of equilibrium models over the past 75 years. Observed in these efforts was their deterministic nature striving to pursue two seemingly competing goals: mathematical elegance and empirical accuracy, the former of which is attractive to mathematical modeling of traffic dynamics, and the latter is required if such modeling is meant to be realistic. As a continued effort of such a pursuit, this paper presents a stochastic speed–density model. The motivation is twofold: first, it is desirable to have a model which achieves both goals reasonably and second, the stochastic model can potentially lead to probabilistic traffic flow modeling and prediction which is typically not offered by a macroscopic approach.