On the fundamental diagram for freeway traffic: A novel calibration approach for single-regime models

Xiaobo Qu, Shuaian Wang and Jin Zhang

Transportation Research Part B: Methodological, 2015, vol. 73, issue C, 91-102

Abstract: The speed-density or flow-density relationship has been considered as the foundation of traffic flow theory. Existing single-regime models calibrated by the least square method (LSM) could not fit the empirical data consistently well both in light-traffic/free-flow conditions and congested/jam conditions. In this paper, first, we point out that the inaccuracy of single-regime models is not caused solely by their functional forms, but also by the sample selection bias. Second, we apply a weighted least square method (WLSM) that addresses the sample selection bias problem. The calibration results for six well-known single-regime models using the WLSM fit the empirical data reasonably well both in light-traffic/free-flow conditions and congested/jam conditions. Third, we conduct a theoretical investigation that reveals the deficiency associated with the LSM is because the expected value of speed (or a function of it) is nonlinear with regard to the density (or a function of it).

Keywords: Traffic volume; Speed; Density; Fundamental diagram; Traffic flow theory (search for similar items in EconPapers)
Date: 2015
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Citations: View citations in EconPapers (21)

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DOI: 10.1016/j.trb.2015.01.001

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