An Efficiency-Based Methodology to Estimate Freeway Capacity: Analytical Properties and Practical Implications

Traditional capacity approaches focus only on the vehicle-carrying ability of a facility while ignoring the practical, well defined purpose of a freeway segment characterized by higher speed. Furthermore, these definitions lead to the two-capacity phenomenon which create confusion among practitioners and researchers over which one is the appropriate value. To address these issues, this paper puts forth a new understanding of freeway capacity by considering the optimal traffic state idea where the infrastructure is operating in the most efficient way. This paper endeavors to explain, based on simple, mathematically-sound rationale, the existence of the optimal traffic state that may lead to a substantial amelioration of traffic conditions on freeways. A case study of ramp metering is undertaken to demonstrate the incorporation of the efficiency-based capacity in real-time traffic control and evaluate the additional benefits that can be achieved. Results show that ramp metering control with efficiency-based capacity reduces the upstream congestion compared to when conventional capacity is used.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee AHB40 Standing Committee on Highway Capacity and Quality of Service.
  • Corporate Authors:

    Transportation Research Board

  • Authors:
    • Siam, Mohammad Rayeedul Kalam
    • Shao, Changqiao
    • Wang, Haizhong
  • Conference:
  • Date: 2019


  • English

Media Info

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

Subject/Index Terms

Filing Info

  • Accession Number: 01698185
  • Record Type: Publication
  • Report/Paper Numbers: 19-05032
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 7 2018 9:48AM