Macroscopic Fundamental Diagram for Brisbane, Australia

Tsubota, Takahiro; Bhaskar, Ashish; Chung, Edward · 2014 · Crossref

DOI: 10.3141/2421-02

archive: archived pipeline: cataloged verified

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Summary

This paper addresses the empirical validation of the Macroscopic Fundamental Diagram (MFD) for signalized arterial networks, specifically within Brisbane, Australia. While previous MFD research focused on highway networks or simulation environments, this study aims to demonstrate the existence and utility of MFDs in real-world urban arterial systems characterized by stop-and-go traffic. The research is motivated by the need for reliable density estimation methods in signalized networks, where traditional point detectors often fail to capture section-wide traffic states due to detector placement and signal phases. The methodology employs a data fusion framework combining stop-line detector counts, signal phase data, and Bluetooth probe vehicle records. To estimate traffic density, the authors utilize the CUmulative plots and Probe Integration for Travel timE estimation (CUPRITE) model. This approach integrates probe vehicle trajectories with cumulative detector counts to correct for counting errors and mid-link sources or sinks, thereby deriving accurate section densities. The study site comprises 155 intersections along radial routes in Brisbane. The network is analyzed as a whole and partitioned into four regions based on physical barriers and network shape, as well as concentric zones based on distance from the city center. Data from October 2012 is used to construct MFDs, which plot area-average flow against accumulation. The results confirm the existence of a well-defined MFD for the Brisbane network, primarily showing a free-flow regime where flow increases with density. However, regional analysis reveals significant variations; Region 2 exhibited a critical regime with a flow peak at a density of 25 veh/km/lane, a feature absent in other regions. The study also demonstrates the MFD’s sensitivity to incidents. In Region 3, abnormal scatters in the MFD corresponded to a major accident on Ipswich Road, capturing the congestion propagation and dissolution dynamics that were not visible in the whole-network MFD. Furthermore, concentric zoning analysis showed that the inner zone (CBD) achieved homogeneous congestion during the morning peak, resulting in a clearer MFD, whereas the outer zone remained heterogeneous due to independent corridor congestion. The significance of this work lies in confirming that appropriate network partitioning is essential for accurate traffic monitoring and control in signalized arterial networks. The findings suggest that MFDs can effectively detect incidents and characterize regional traffic performance, provided the network is divided into homogeneous zones. This supports the application of MFD-based strategies, such as perimeter control and congestion pricing, in urban environments with radial geometries. The study highlights that network geometry and incident impacts necessitate spatial partitioning to reveal underlying traffic dynamics that are obscured in aggregate network-wide analyses.

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• traffic density