Citation

Ackeret KW. ITE J. 1994; 64(12): 27-33.

Copyright

(Copyright © 1994, Institute of Transportation Engineers)

DOI

unavailable

PMID

unavailable

Abstract

Transportation engineers are employing triple left-turn lanes to handle at-grade intersection locations with severe left-turn capacity and operational problems where land-use constraints and construction costs preclude a grade-separated interchange. These triple left-turn configurations are relatively new, leaving engineers to base design schemes on personal experience and the familiar dual left-turn lanes. This article presents general criteria for the geometric design of triple left-turn lanes and is based on the design and operational experiences of engineers in the Las Vegas Metropolitan area. Three configurations are reviewed: 1) exclusive triple left-turn lane, all lanes shadowed, 2) exclusive triple left-turn lane, outside trap lane, and 3) permissive triple left-turn lane, outside lane optional. In addition to design criteria, the article discusses installation, roadway delineation and signage, and signal design.