Citation

Leonard II JD. Transp. Res. Rec. 1994; 1457: 104-110.

Copyright

(Copyright © 1994, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

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: en

Keywords

Electronic equipment; Intersections; Traffic signals; Highway traffic control; Highway systems; Queueing theory