ANALYSIS OF UNSIGNALIZED INTERSECTION CAPACITY

The conceptual bases of unsignalized intersection capacity procedures from the Swedish Capacity Manual and from the Interim U.S. Capacity Manual are compared, and the procedures are evaluated with field data from four intersections in the Chicago, Illinois, region. The Swedish method, based on principles of queueing theory and using parameters reflecting Swedish conditions, grossly overestimated capacity and underestimated delay. The empirically based U.S. method substantially underestimated capacity, resulting in level of service values that were approximately one level of service too low. Causes of the poor estimation included critical gaps that were too small in the Swedish method and too large in the U.S. method and inappropriate definitions of dominant volumes. Based on the conceptual and empirical comparisons, critical gaps were revised and dominant volumes were redefined in both methods. Evaluations of these revised procedures revealed much closer correspondence to field-measured values for capacity and delay. With revised critical gaps, the interim U.S. method appears to correspond fairly well with field data. The Swedish method, however, contained errors in capacity and delay estimates that were traced to probable differences in driver performance and traffic conditions in Sweden and in the United States. Preliminary tests of the Swedish delay model indicate that it can provide very accurate delay estimates if it is revised to reflect U.S. drivers and driving conditions.

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1984/971/971-004.pdf
• Record URL:
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• Supplemental Notes:
  • Publication of this paper sponsored by Committee on Highway Capacity and Quality of Service. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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• Authors:
  • Bakare, Adebayo B
  • Jovanis, Paul P
• Publication Date: 1984

Media Info

• Media Type: Print
• Features: Figures; References; Tables;
• Pagination: pp 21-31
• Monograph Title: TRAFFIC CAPACITY AND CHARACTERISTICS
• Serial:
  • Transportation Research Record
  • Issue Number: 971
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Accuracy; Highway capacity; Innovation; Queuing theory; Traffic delays; Unsignalized intersections
• Old TRIS Terms: Concepts; Queueing theory
• Subject Areas: Highways; Operations and Traffic Management; I71: Traffic Theory;

Filing Info

• Accession Number: 00396832
• Record Type: Publication
• ISBN: 0309037530
• Report/Paper Numbers: HS-038 730
• Files: HSL, TRIS, TRB
• Created Date: Jan 31 1986 12:00AM