Safety Performance of Split Versus Lead-Lag Traffic Signals in Abu Dhabi
In Abu Dhabi City, United Arab Emirates, the traffic signals of a total of 38 signalized intersections have been modified. The old design was a split phasing system for all intersections’ approaches while the new system is protected-only lead-lag phasing system on the two major-road approaches and split system on the minor-road approaches. This modification was done for operations and capacity reasons and occurred in years 2009 and 2010. Same intersections have also experienced changes in the phasing system to include end-of-green flash interval in year 2009 besides changes in the speed limit. Analysis of crash data has indicated traffic safety deterioration after the signals modifications; especially with left-turn movements. The main objective of this study is to examine the influence that the occurred changes may have on the intersection safety performance. Out of the 38 intersections, only 17 have been considered since major geometry changes have been implemented for the rest of intersections. Severe crashes from years 2008 to 2012 have been used for this reason. Results indicated that 86 % of crashes in year 2012 at those intersections were classified as right-angle between left turn and opposite through movements. For such crashes, drivers on the left-turn were described as at-fault. Those crashes resulted in 9 fatalities only in year 2012. Results showed that intersections within the central business district (CBD) experienced an increase of 300% for crashes between left-turn and through movements. Moreover, intersections’ approaches outside CBD that have experienced changes in the speed limit from 60 km/h to 80 km/h after the signal changes experienced an increase of 350 % for the same crash type.
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Supplemental Notes:
- This paper was sponsored by TRB committee AHB25 Traffic Signal Systems.
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Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- Sarhan, Mohamed
- Garib, Atef
- Al Ghafli, Abdulla
- Al-Harthei, Hussain
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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; Tables;
- Pagination: 10p
- Monograph Title: TRB 93rd Annual Meeting Compendium of Papers
Subject/Index Terms
- TRT Terms: Before and after studies; Crash rates; Exclusive phasing; Lead-lag phasing; Signalized intersections; Traffic safety
- Geographic Terms: Abu Zaby (United Arab Emirates)
- Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors; I73: Traffic Control; I81: Accident Statistics; I82: Accidents and Transport Infrastructure;
Filing Info
- Accession Number: 01520398
- Record Type: Publication
- Report/Paper Numbers: 14-4701
- Files: TRIS, TRB, ATRI
- Created Date: Mar 28 2014 11:06AM