ESTIMATION OF LEFT-TURN SATURATION FLOWS

This paper addresses the problem of estimating left-turn saturation flows at both signalized and unsigalized intersections. The best known methods for estimating this traffic measure were tested for reliability against field data. A new approach to the problem is also presented. The results are applicable to left-turning traffic flowing through gaps of suitable size in the opposing traffic without the protection of a special signal phase. Both one and two lanes of opposing traffic were considered, as were unsignalized intersections. The gap-acceptance functions that best represent the behavioral patterns of left turners at these intersections are also presented. Time-lapse photography was used to collect data at five different intersections in upstate New York. Approximately 4000 completed left-turning movements were observed. Using these field observations, the ability of several existing methods to estimate left-turn saturation flow was tested by standard statistical analysis techniques. Adjustments were made for any divergence from actual conditions. Most of the original models do not reflect real-world conditions, so a new model is proposed for each type of intersection. The resutls indicate that the gap-acceptance characteristics of left-turners can be accurately described by a uniform cumulative density function. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 35-41
  • Monograph Title: Highway capacity, measures of effectiveness, and flow theory
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00189848
  • Record Type: Publication
  • Report/Paper Numbers: HS-025 846
  • Files: TRIS, TRB
  • Created Date: Apr 12 1979 12:00AM