Logistic modeling of the equilibrium speed-density relationship |
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Authors: | Haizhong Wang |
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Institution: | a Department of Civil and Environmental Engineering, University of Massachusetts Amherst, MA 01003, United States b Department of Mathematics and Statistics, University of Massachusetts Amherst, MA 01003, United States |
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Abstract: | The fundamental diagram, as the graphical representation of the relationships among traffic flow, speed, and density, has been the foundation of traffic flow theory and transportation engineering. Seventy-five years after the seminal Greenshields model, a variety of models have been proposed to mathematically represent the speed-density relationship which underlies the fundamental diagram. Observed in these models was a clear path toward two competing goals: mathematical elegance and empirical accuracy. As the latest development of such a pursuit, this paper presents a family of speed-density models with varying numbers of parameters. All of these models perform satisfactorily and have physically meaningful parameters. In addition, speed variation with traffic density is accounted for; this enables statistical approaches to traffic flow analysis. The results of this paper not only improve our understanding of traffic flow but also provide a sound basis for transportation engineering studies. |
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Keywords: | Logistic speed-density model Generalized logistic curve Fundamental diagram |
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