The scope and magnitude of the oversaturation problem was defined and the way it may best be combatted with existing methods was determined. The paper reports the beginning of a research process leading to improved operation and controls for oversaturated networks. Six specific objectives of the research are listed. The project was planned in three phases. Phase I was concerned with the definition of the problem and determination of its scope and magnitude. Phase II covered the examination and evaluation of existing traffic control techniques. The third phase dealt with the description of advanced methods of traffic control and with the formulation of a detailed plan and program for test and application of the recommended procedures. The first phase was accomplished by a questionnaire surveys of cities, counties and states in the U.S. and Canada. A figure is presented which illustrates the variation of saturation reported by city size for CBD signalized intersections and for all intersections on the arterial system. The que length characteristics at congested intersections is illustrated by a figure which gives an indication of the range of oversaturated intersection experiences by city size. Information on the means used for timing signals is tabulated. Measures of effectiveness to characterize particular aspects of traffic performance are categorized, and a set of que-related measures was selected as being the most promising for study. In the second phase of the study, a literature review and survey response, identified four causes of congestion. The most effective measures for alleviating the problem are listed. It was found that operational measures leading to increased link storage were more effective in delaying or eliminating oversaturation than were measures aimed at increasing intersection capacity. Some particular findings with respect to signal techniques are presented. In the third phase, 4 relevant advanced control concepts were selected from a review of the literature and each was subjected to an extensive simulation evaluation using three different test networks. The research conducted as part of this study has demonstrated that many existing operations and control techniques can be applied to the reduction or elimination of oversaturation.

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  • Supplemental Notes:
    • This is a digest of the essential findings from the final report on NCHRP Project 3-18(2), "Traffic Control in Oversaturated Street Networks." 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

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Publication Date: 1973-12

Media Info

  • Media Type: Digital/other
  • Features: Figures; Tables;
  • Pagination: 9 p.
  • Serial:
  • Publication flags:

    Open Access (libre)

Subject/Index Terms

Filing Info

  • Accession Number: 00272111
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 19 1974 12:00AM