Network Fundamental Diagram for Hierarchical Ramp Metering in Freeways

Recent studies on aggregated traffic modeling of urban networks have shown the existence of a well-defined and low-scatter Macroscopic Fundamental Diagram (MFD) that links network aggregated flow and density. However, the MFD of freeway networks typically exhibits high scatter and hysteresis loops that challenge the monitoring capability and control performance of MFD-based congestion management schemes in freeways. In this paper, the authors introduce a model to capture the evolution of density heterogeneity which is essential to reproduce the dynamics of freeway MFD accurately. The proposed model is incorporated in a hierarchical control structure for coordinated ramp metering on a freeway stretch with multiple congestion bottlenecks and on- and off-ramps. At the upper level, a model predictive control (MPC) approach is developed to optimize total inflow from on-ramps to the freeway stretch, where the prediction model is formulated based on the proposed MFD model. The lower level controller distributes the optimal total inflows to each on-ramp of the freeway based on local traffic state feedback. The proposed ramp metering framework shows desirable performance to reduce the total time spent and eliminate congestion. Simulation outcomes highlight that the MFD-based hierarchical controller (i) is better able to overcome the modeling mismatch between the prediction model and the plant (process model) in the MPC framework and (ii) requires less computation effort than other nonlinear controllers.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AHB45 Standing Committee on Traffic Flow Theory and Characteristics.
• Authors:
  • Han, Yu
  • Ramezani, Mohsen
  • Hegyi, Andreas
  • 0000-0002-0399-0703
  • Yuan, Yufei
  • Hoogendoorn, Serge
• Conference:
  • Transportation Research Board 97th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2018-1-7 to 2018-1-11
• Date: 2018

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 19p

Subject/Index Terms

• TRT Terms: Bottlenecks; Congestion management systems; Freeways; Off ramps; On ramps; Ramp metering; Simulation
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 01659916
• Record Type: Publication
• Report/Paper Numbers: 18-01540
• Files: TRIS, TRB, ATRI
• Created Date: Feb 13 2018 9:52AM