Citation

Spring GS, Thomas A. J. Transp. Eng. 1999; 125(2): 138-143.

Copyright

(Copyright © 1999, American Society of Civil Engineers)

DOI

unavailable

PMID

unavailable

Abstract

Given the increasing use of double left-turn lanes and the lack of methods to design and analyze them, there exists an urgent need to develop such methods. This paper describes work completed at North Carolina A and T State University that expands the scope of previous work done in the area of double left-turn lanes and improves the scientific basis of that work. Double left-turn data from 30 intersections in the city of Greensboro, North Carolina, were analyzed with respect to relationships among performance and geometric characteristics. Results indicate that the overall f(LT) of 0.92, recommended by the Highway Capacity Manual, appears reasonable for the inside lane. Values of 0.86-0.88 are more appropriate for outside lane adjustments. The variables causing the most significant changes in performance of double left-turn lanes were traffic related, and not related to geometry. The presence or absence of through traffic and the absence of opposing left-turn flow were key causes of performance changes.