Methods are given for calculating timings and estimating the capacities and operating characteristics of signalised intersections. Saturation flows, that is the rates at which vehicles can cross the stopline during the period that a green signal is showing, are calculated in terms of the number and types of lanes. Saturation flows are expressed in terms of through-car units (tcu's) per hour. Adjustments are given for lane width, gradient, kerb lane usage, parking effect of trams. The intersection degree of saturation, X, is the flow/capacity ratio which is the same for each traffic movement representative of its phase. This is obtained when the effective green times are made proportional to the critical y values (flow/saturation flow ratios) for each phase. For preliminary design and planning purposes, a value of x less than 0.90 is recommended as a measure of satisfactory operating conditions, and 0.95 should be regarded as an absolute limit. A detailed treatment of the subject of lost time is presented. Methods are described for identifying critical movement, calculating intersection flow ratio and lost time for cases including overlap (split) phase cases. Formulae are given for calculating delays, queue lengths, probability of clearing queues for vehicles as well as pedestrian movements, and right turn queue storage distances. Numerical examples are given to illustrate each type of calculation. (A). (TRRL)

  • Corporate Authors:

    ARRB Group Ltd.

    Vermont South, Victoria  Australia 
  • Publication Date: 1979-6

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 73 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00303530
  • Record Type: Publication
  • Source Agency: ARRB Group Ltd.
  • Report/Paper Numbers: AIR 288-2 Monograph
  • Files: ITRD, TRIS, ATRI
  • Created Date: Feb 11 1980 12:00AM