OPERATIONAL CHARACTERISTICS OF TRIPLE LEFT TURNS

A study of the characteristics of triple left turns was performed. Five triple-left-turn sites in Orange County, California, were identified. Manual saturation flow rate studies at each site were performed using electronic counter boards. Queue discharge times and vehicle arrivals were compiled for all vehicles by lane and by signal cycle. Across all five sites, a sample consisting of 4,742 lane cycles and 34,898 vehicles was compiled for analysis. On average, these triple left turns supported flows of 795 vehicles per hour, received a 19% split of the total cycle time and spent 57% of that split time servicing the queue. Computing the saturation flow rate using the method suggested by the 1985 Highway Capacity Manual, the average saturation flow rate observed was 1,930 vehicles per hour of green per lane. Variations in the saturation flow rate observed at the triple-left-turn sites were explored. Results reveal no significant differences in saturation flow rates when categorized by site, by weekdays (Monday through Friday), or by observer. Significant differences were observed between lanes (e.g., inner and middle versus outer), time of day (e.g., morning, midday, and evening) and weekday versus weekend.

Language

  • English

Media Info

  • Features: Photos; References; Tables;
  • Pagination: p. 104-110
  • Monograph Title: Part 1: 1994 TRB Distinguished Lecture, Adolf D May; Part 2: Traffic flow and capacity
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00677652
  • Record Type: Publication
  • ISBN: 0309061008
  • Files: TRIS, TRB
  • Created Date: May 11 1995 12:00AM