To Investigate the Hidden Gap between Traffic Flow Fundamental Diagrams and the Derived Microscopic Car Following Models: A Theoretical Analysis
Paper i proceeding, 2020

Traffic flow fundamental diagram, or simply speed–density relationship and/or flow–density relationship, is the basis of traffic flow theories and road performance studies since it depicts the mathematical relationship among three traffic flow fundamental parameters—density, speed, and traffic flow. In this paper, through mathematical analyses and simulations, we find that for all existing fundamental diagram models, their derived microscopic car following models do not perform well and cannot reproduce the status of the stable flow described by the corresponding fundamental diagrams. The results indicate that there seems to exist a hidden gap between existing traffic flow fundamental diagrams and the corresponding microscopic car following models. We further discuss about the fundamental causes behind such gap and propose a simple yet incomplete solution at the end of this paper.

Fundamental diagram

Mathematical analysis

Traffic flow

Road performance

Stable flows

Car following models

Traffic flow theory

Mathematical relationship

Traffic control


Yang Yu

University of Technology Sydney

Jie Zhu

Chalmers, Arkitektur och samhällsbyggnadsteknik, Geologi och geoteknik

Xiaobo Qu

Chalmers, Arkitektur och samhällsbyggnadsteknik, Geologi och geoteknik

Smart Innovation, Systems and Technologies

2190-3018 (ISSN)

Vol. 185 89-98

3rd KES International Symposium on Smart Transportation Systems, KES-STS 2020
Split, Croatia,




Transportteknik och logistik




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