The Effect of Priority Reversal on Delay and Queue Length at Roundabouts
The procedure for analyzing roundabout operations in the 2010 U.S. Highway Capacity Manual is based on the assumption of absolute priority to circulating traffic. Entering drivers have to seek for sufficient gaps in order to merge. However observations at roundabouts operating at or near capacity show reversed or shared priority between entering and circulating vehicles. This phenomenon has been reported elsewhere to influence the capacity, delay and queue length of roundabouts. To study the effects of reversed priority on the performance of roundabouts in the U.S., a roundabout in Fernley, Nevada, operating at capacity for the P.M. peak period was observed. The driver behavior characteristics were extracted together with the geometric parameters. Based on the observed driver behaviors and traffic flow characteristics, three scenarios were modeled using the micro-simulation software VISSIM. Results obtained after multiple simulation runs showed that roundabout performance improved with increasing periods of reversed priority: delay reduced by 8-16 percent and queue length reduced by 10-20 percent for every 10 percent increase in “reversed priority periods”. It was also shown that, as the priority reversal period increased, the influence of the size of inscribed diameter decreased even though an improvement in performance was observed. When the intersection experienced traffic volume increase the performance of the roundabout decreased until it reached a threshold level where it appeared to remain constant.
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Supplemental Notes:
- This paper was sponsored by TRB committee AHB40-1 Highway Capacity and Quality of Service Special Paper Review Coordination.
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Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- Ahiamadi, Samuel Kofi
- Tian, Zong Z
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Conference:
- Transportation Research Board 93rd Annual Meeting
- Location: Washington DC
- Date: 2014-1-12 to 2014-1-16
- Date: 2014
Language
- English
Media Info
- Media Type: Digital/other
- Features: Figures; References;
- Pagination: 15p
- Monograph Title: TRB 93rd Annual Meeting Compendium of Papers
Subject/Index Terms
- TRT Terms: Highway capacity; Measures of effectiveness; Queuing; Roundabouts; Traffic delays; Traffic volume
- Uncontrolled Terms: Roundabout capacity
- Geographic Terms: Nevada
- Subject Areas: Data and Information Technology; Highways; Operations and Traffic Management; I72: Traffic and Transport Planning; I73: Traffic Control;
Filing Info
- Accession Number: 01517514
- Record Type: Publication
- Report/Paper Numbers: 14-1912
- Files: TRIS, TRB, ATRI
- Created Date: Mar 10 2014 9:23AM