USE OF THE NCHRP SIGNALIZED INTERSECTION CAPACITY METHOD--A SOUTH AFRICAN EXPERIENCE

The primary objective of this study was to assess the applicability of the proposed NCHRP operations method for signalized intersection capacity analysis to South African traffic conditions. Secondary objectives were first, to review the reactions of 90 engineers who received a 5-day intensive course on the use of the NCHRP method and second, to draw a comparison between the predictions of this new method, those that could be obtained using the Highway Capacity Manual (HCM) method, and the relevant fieldmeasured data. The analysis was based on applying the proposed NCHRP Operations Method to ten South African intersection data sets for which not only input data but also field measurements of lane saturation flows, stopped delays, queue lengths, and percent vehicles stopped were available. The ten intersections varied from simple geometrically designed intersections with pretimed two-phase signals to more complicated intersections with actuated multiphase signals. The NCHRP method is validated by evaluating its predictive accuracy under conditions experienced at the ten South African intersections. The validation is supplemented by the following analyses: a comparison of lane saturation flows using the proposed NCHRP and HCM methods, factors influencing saturation flows, the possibility of a default value for saturation flow, an assessment of stopped delay predictions using measured saturation flow as input, and an assessment of permissive left-turn stopped delays. The conclusions include the identification of the strengths and weaknesses of the NCHRP method under South African traffic conditions and the identification and quantification of alternative procedures and default values that would enhance the method's application in that country. In general, the proposed NCHRP method providse accurate results, and its ability to estimate saturation flow is better than that of the HCM method. One of the findings was that the use

Media Info

  • Media Type: Print
  • Features: References; Tables;
  • Pagination: pp 32-40
  • Monograph Title: TRAFFIC CAPACITY AND CHARACTERISTICS
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00396833
  • Record Type: Publication
  • ISBN: 0309037530
  • Report/Paper Numbers: HS-038 731
  • Files: HSL, TRIS, TRB
  • Created Date: Jan 31 1986 12:00AM