PEAK-PERIOD TRAFFIC DELAYS AT ROAD JUNCTIONS AND OTHER BOTTLENECKS

A flow/delay relationship for major/minor priority junctions discussed in an earlier paper has been found to be valuable in that it avoids difficulties associated with steady-state queueing relationships, which predict infinite delays when demand reaches capacity, and deterministic methods which in most cases substantially underestimate delays. In this paper the authors describe a development of this relationship which allows the effects of changes of capacity during peak periods and of non-zero flows in the adjacent-to-peak periods to be evaluated explicitly. The approach is concerned with the low-definition problem associated with long-timescale approaches for economic evaluation, where the fine detail of queue length variation is less important. Simple formulae are developed which allow the average delay generated by peak-period traffic to be evaluated, given only (1) the average demand and capacity during the peak period; (2) the average demand and capacity during the adjacent-to-peak periods; and (3) the duration of the peak. These formulae take into account the build-up and decay of demand during the peak period, which it is suggested can be evaluated by means of a pocket calculator. The relationships derived refer to individual traffic streams but in later sections of the paper their consequences for whole junctions are examined. An important application of the results presented in this paper is considered to be the assessment of comparative junction delays. Reference is made to a program, developed at the Transport and Road Research Laboratory to compare delays at different types of junction in this way, and which will incorporate the results presented in this paper, as well as new capacity formulae for roundabout entries and major/minor priority junctions when they shortly become available. /TRRL/

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  • Corporate Authors:

    Printerhall Limited

    29 Newmart Street
    London W1P 3PE,   England 
  • Authors:
    • KIMBER, R M
    • Hollis, E M
  • Publication Date: 1978-10

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Filing Info

  • Accession Number: 00193970
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Report/Paper Numbers: N10
  • Files: ITRD, TRIS
  • Created Date: May 26 1979 12:00AM