A FURTHER INVESTIGATION ON CRITICAL GAP AND FOLLOW-UP TIME

The 1997 update to the "Highway Capacity Manual" (HCM) includes a new set of critical gap and follow-up time values calibrated based on the U.S. conditions. This paper is to present the detailed investigation on various factors affecting the critical gap and follow-up time, so that users can have a better understanding of the recommended critical gap and follow-up time values. The investigation was based on the comprehensive database established during the NCHRP 3-46 project, Capacity and Level of Service at Unsignalized Intersections. The paper first identifies various factors that might affect critical gap and follow-up time, such as intersection geometry, traffic movements, vehicle type, speed limits, and delay. Step-wise regression technique is then applied to identify the significance of these various factors. The relationship between critical gap and follow-up time values is also investigated. It is found that the major factors affecting critical gap and follow-up time include intersection geometry, vehicle type, approach grade, and traffic movements. While an independent set of follow-up time values are recommended, the follow-up time to critical gap ratio is found to be approximately 0.60, which has been reported in previous studies. The newly recommended set of critical gap and follow-up time values form the basis for the procedures for two-way stop-controlled intersections included in the 1997 update to the HCM and the 2000 HCM.

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  http://onlinepubs.trb.org/onlinepubs/circulars/ec018/ec018toc.pdf
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• Supplemental Notes:
  • 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
• Corporate Authors:

  Transportation Research Board

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• Authors:
  • Tian, Z Z
  • Troutbeck, R
  • Kyte, M
  • Brilon, W
  • Vandehey, M
  • Kittelson, W
  • Robinson, B
• Conference:
  • Fourth International Symposium on Highway Capacity
  • Location: Maui, Hawaii
  • Date: 2000-6-27 to 2000-7-1
• Publication Date: 2000-6

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 397-408
• Serial:
  • Transportation Research Circular
  • Issue Number: E-C018
  • Publisher: Transportation Research Board
  • ISSN: 0097-8515

Subject/Index Terms

• TRT Terms: Geometric design; Highway capacity; Highway grades; Level of service; Regression analysis; Traffic flow; Unsignalized intersections; Vehicle classification
• Identifier Terms: Highway Capacity Manual
• Uncontrolled Terms: Critical gap; Follow-up time; Two-way stop control
• Subject Areas: Data and Information Technology; Highways; Operations and Traffic Management; Planning and Forecasting; I72: Traffic and Transport Planning;

Filing Info

• Accession Number: 00795396
• Record Type: Publication
• Report/Paper Numbers: E-C018
• Files: TRIS, TRB
• Created Date: Jul 26 2000 12:00AM