The conceptual bases of unsignalized intersection capacity procedures from the Swedish Capacity Manual and from the Interim U.S. Capacity Manual are compared, and the procedures are evaluated with field data from four intersections in the Chicago, Illinois, region. The Swedish method, based on principles of queueing theory and using parameters reflecting Swedish conditions, grossly overestimated capacity and underestimated delay. The empirically based U.S. method substantially underestimated capacity, resulting in level of service values that were approximately one level of service too low. Causes of the poor estimation included critical gaps that were too small in the Swedish method and too large in the U.S. method and inappropriate definitions of dominant volumes. Based on the conceptual and empirical comparisons, critical gaps were revised and dominant volumes were redefined in both methods. Evaluations of these revised procedures revealed much closer correspondence to field-measured values for capacity and delay. With revised critical gaps, the interim U.S. method appears to correspond fairly well with field data. The Swedish method, however, contained errors in capacity and delay estimates that were traced to probable differences in driver performance and traffic conditions in Sweden and in the United States. Preliminary tests of the Swedish delay model indicate that it can provide very accurate delay estimates if it is revised to reflect U.S. drivers and driving conditions.

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 21-31
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00396832
  • Record Type: Publication
  • ISBN: 0309037530
  • Report/Paper Numbers: HS-038 730
  • Files: HSL, TRIS, TRB
  • Created Date: Jan 31 1986 12:00AM