A set of procedures are presented for relating peak-hour volumes, geometric design, and alternate signal phasing strategies with overall level of service. The procedures allow estimation of future traffic conditions for development planning, and are thus of value in the study of traffic impact on the environment. Existing and future critical intersections throughout a study area may be identified and indicated graphically in a simple way, using the "Intersection Capacity Utilization" (IGU) value on the area map. ICU is defined as "the sum of the ratios of approach volume divided by approach capacity for each leg of intersection which controls overall traffic signal timing plus an allowance for clearance times." There are weaknesses in the overall capacity calculation procedures, which require further refinement and research. The method assumes optimal signal operation and timing, which too often is not the case. In addition, the calculation method infers that longer cycle lengths with fewer yellow clearance periods would lead to lower ICU and improved operations, which is definitely not the case. Adjustments for time lost due to the inefficiencies of signal coordination systems, maximum pedestrian crossing times and other factors must also be made. Even so, the general relationships stated in this paper provide a valuable tool for the evaluation of present and future traffic conditions for a wide range of alternatives in signal operations for an individual location or an areawide study.

  • Corporate Authors:

    Institute of Traffic Engineers

    2029 K Street, NW
    Washington, DC    20006
  • Authors:
    • Crommelin, R W
  • Publication Date: 1974-7

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 11-14
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00260469
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 11 1974 12:00AM