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

    Author(s)
    Qu, Xiaobo
    Wang, Shuaian
    Zhang, Jin
    Griffith University Author(s)
    Zhang, Jin
    Qu, Xiaobo
    Year published
    2015
    Metadata
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    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 ...
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    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).
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    Journal Title
    Transportation Research Part B
    Volume
    73
    DOI
    https://doi.org/10.1016/j.trb.2015.01.001
    Subject
    Applied mathematics
    Civil engineering
    Transport engineering
    Transportation, logistics and supply chains
    Publication URI
    http://hdl.handle.net/10072/69322
    Collection
    • Journal articles

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