Development of left-turn lane guidelines for signalized and unsignalized intersections
By: Vijayendra R. Lakkundi ... [et al.].
Contributors: Lakkundi, Vijayendra R.; Virginia Transportation Research Council.; Virginia. Dept. of Transportation.; United States. Federal Highway Administration.
Series: VTRC ;; 04-R11; VTRC (Series) ;; 04-R11.
Publisher: Virginia Transportation Research Council
Published: 2004
Place of publication: Charlottesville, Va
Language: eng
Number of pages: 69
Subjects: Left-turn lanes.; Roads -- Interchanges and intersections.; Traffic flow.; level of service.; signalized intersections.; unsignalized intersections.
Description: It is generally accepted that the level of service (LOS) at intersections significantly affects the overall LOS of the road system. It is also known that the LOS at an intersection can be adversely affected by frequently allowing left-turning vehicles to block through traffic. In addition, crash rates tend to be higher at intersections than on through sections of a road. The separation of left-turning vehicles from through traffic is therefore an important condition for the safe and effective operation of intersections. Existing guidelines for installing left-turn lanes have several limitations. They are mainly based on the traffic volumes at the intersection, and they use deterministic models with fixed gap acceptance and/or left-turn maneuver times. In addition, the guidelines for left-turn lanes for unsignalized intersections and signalized intersections must be specific for the type of intersection. In this study, new left-turn guidelines for both unsignalized and signalized intersections were developed on the basis of well-validated event-based simulation programs. Guidelines for unsignalized intersections were based on the percentage of left turns blocking through vehicles, whereas the guidelines for signalized intersections were developed using a minimum left-turn volume of either 85% left-turn capacity or LOS E delay (55 seconds/vehicle). In addition to the general guidelines, a prioritization tool that can be used to prioritize candidate intersections was developed. The prioritization tool accounts for both operational and safety aspects.
Notes: Includes bibliographical references (p. 46-47).
"March 2004."
Performed by Virginia Transportation Research Council for Virginia Department of Transportation and U.S. Federal Highway Administration under contract no. 60597
Also available online (Adobe Acrobat Reader required) via the Virginia Transportation Research Council website http://www.virginiadot.org/vtrc/main/index%5Fmain.htm.
Final report; September 2001-December 2003.