00622236

Component

http://onlinepubs.trb.org...trr/1991/1327/1327-012.pdf

https://scholar.google.co...orty&publication_year=1991

At an unsignalized T-intersection, where a major two-lane roadway intersects a minor roadway, criteria that justify a left-turn lane on the major roadway are analyzed. Three criteria are considered: (a) probability that one or more waiting through vehicles are present on the approach; (b) delay (average delay to the "caught" through vehicles, average delay to all through vehicles, and delay savings due to the left-turn lane); and (c) degradation of the level of service. The volume combinations (through, left-turn, and opposing flow) that would justify a left-turn lane under each of the criteria are presented. The current AASHTO guidelines are based on the probability that one or more through vehicles are in the queue behind a waiting left-turn vehicle. The original mathematical formulation of the AASHTO guidelines is examined and corrected, and a new set of volume warrants is developed. A simulaiton model of the movements of the vehicles on the approach is simulated, and delays to through vehicles with and without a left-turn lane for different traffic volumes are computed. Finally, a set of traffic volumes at which the level of service of the approach changes from A to B is developed. The warrant volumes based on the three criteria are different. Delay and the level of service are more easily understandable measures of traffic performance than probability, so the volume combinations based on these two criteria should also be considered. The result provides a range of volume combinations within which an engineering judgment should be made. Discussions of other considerations for justification of a left-turn lane are also provided.

This paper appears in Transportation Research Record No. 1327, Visibility, Rail-Highway Grade Crossings, and Highway Improvement Evaluation 1991. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

01407196

p. 80-88

1991

Transportation Research Record

0309051673

Figures (7) ; References (10) ; Tables (4)

Arterial highways; Left turn lanes; Level of service; Simulation; T intersections; Traffic delays; Traffic volume; Two lane highways; Unsignalized intersections; Warrants (Traffic control devices)

Highways; Operations and Traffic Management; I73: Traffic Control

TRIS, TRB, ATRI

May 31 1992 12:00AM

• COLOR AND SHAPE RECOGNITION OF REFLECTORIZED TARGETS UNDER AUTOMOBILE LOW-BEAM ILLUMINATION AT NIGHT
• CONDITIONAL ANALYSIS OF ACCIDENTS AT FOUR-APPROACH TRAFFIC CIRCLES
• CONFLICTS AT TRAFFIC CIRCLES IN NEW JERSEY
• ESTIMATING ACCIDENT POTENTIAL OF ONTARIO ROAD SECTIONS
• FUEL SAVINGS THROUGH TRAFFIC SIGNAL HARDWARE IMPROVEMENTS
• INNOVATIVE EVALUATIONS OF TRAFFIC SYSTEM MANAGEMENT MEASURES FOR POSTEARTHQUAKE PROJECTS IN OAKLAND, CALIFORNIA
• LOW-CLEARANCE VEHICLES AT RAIL-HIGHWAY GRADE CROSSINGS: AN OVERVIEW OF THE PROBLEM AND POTENTIAL SOLUTIONS
• PRACTICAL DETERMINATION OF TUNNEL ENTRANCE LIGHTING NEEDS
• PRIORITY PROGRAMMING METHODOLOGY FOR RAIL-HIGHWAY GRADE CROSSINGS
• SAFETY EVALUATION OF CONVERTING ON-STREET PARKING FROM PARALLEL TO ANGLE
• VISIBILITY UNDER TRANSIENT ADAPTATION