Modeling the Impacts of Heavy Vehicle and Geometry on Roundabout Entry Capacity

Entry capacity is one of the most important indices used to predict roundabout operational performance and its ability to accommodate the expected traffic demand. Existing procedures, such as the proposed ones by Highway Capacity Manual HCM (2016) and the Japan Roundabout Manual JRM (2016), estimate entry capacity using the gap acceptance theory by defining fixed values for the gap parameters in circulating and entry flows without considering the impact of roundabout geometry. In reality, roundabouts are being constructed with different layouts, which may leave significant impacts on driver behavior and the achieved entry capacities. This study aims at analyzing the impacts of roundabout geometry and heavy vehicles on the gap parameters as well as the estimated entry capacity. Empirical data are collected by video surveys at eight roundabouts in Japan. Then using image-processing software, gap parameters are extracted from video records. The empirical analysis verified the significant influence of geometric elements on gap parameters and entry capacity. The developed methodology for the estimation of entry capacity can reliably quantify the impact of heavy vehicle ratios in the entry approach and the circulatory roadway as well as roundabout geometric layout.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee AHB40 Standing Committee on Highway Capacity and Quality of Service.
  • Authors:
    • Zhao, Yujia
    • Zhang, Xin
    • Alhajyaseen, Wael K M
    • Nakamura, Hideki
  • Conference:
  • Date: 2018


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 18p

Subject/Index Terms

Filing Info

  • Accession Number: 01660958
  • Record Type: Publication
  • Report/Paper Numbers: 18-06066
  • Files: TRIS, TRB, ATRI
  • Created Date: Jan 8 2018 11:34AM