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Coordinating, Developing, and Delivering Highway Transportation Innovations

 
REPORT
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Publication Number:  FHWA-HRT-19-036    Date:  August 2020
Publication Number: FHWA-HRT-19-036
Date: August 2020

 

Safety Evaluation of Flashing Yellow Arrow At Signalized Intersections

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FOREWORD

The research documented in this report was conducted as part of the Federal Highway Administration's (FHWA's) Evaluation of Low-Cost Safety Improvements Pooled Fund Study (ELCSI-PFS). FHWA established this PFS in 2005 to conduct research on the effectiveness of the safety improvements identified by the National Cooperative Highway Research Program's Report 500 Series as part of the implementation of the American Association of State Highway and Transportation Officials Strategic Highway Safety Plan.(1) The ELCSI-PFS studies provide a crash modification factor and benefit-cost (B/C) economic analysis for each of the targeted safety strategies identified as priorities by the pooled fund member States.

This study evaluated the safety effectiveness of the flashing yellow arrow (FYA) treatment at signalized intersections in reducing the frequency of left-turn crashes. The study divided the treatments into seven categories depending on the phasing system in the before period. The first five categories had permissive or protected-permissive phasing in the before period and experienced a reduction in left-turn crashes and left-turn-with-opposing-through crashes at the intersection level. Intersections in categories 6 and 7 had at least one protected left-turn phase in the before period, and after phasing had an FYA protected-permissive left-turn phase without time-of-day operation (category 6) and with time-of-day operation (category 7). These categories experienced an increase in left-turn and left-turn-with-opposing-through crashes. Economic analysis for categories 1-5 showed the treatment is cost effective in improving safety. B/C analyses were not conducted for categories 6 and 7 because these treatments are typically used for capacity improvements rather than safety. This report will benefit safety and traffic engineers and safety planners by providing greater insight into intersection safety.

Brian P. Cronin, P.E.
Director, Office of Safety and Operations
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

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Technical Report Documentation Page
1. Report No.
FHWA-HRT-19-036
2. Government Accession No. 3. Recipient’s Catalog No.
4. Title and Subtitle
Safety Evaluation of Flashing Yellow Arrow at Signalized Intersections
5. Report Date
August 2020
6. Performing Organization Code
7. Author(s)
Raghavan Srinivasan (ORCID: 0000-0002-3097-5154),
Bo Lan (ORCID: 0000-0002-7998-7252),
Daniel Carter (ORCID: 0000-0001-6572-6548),
Sarah Smith, and Kari Signor
8. Performing Organization Report No.
9. Performing Organization Name and Address
VHB
940 Main Campus Drive, Suite 500
Raleigh, NC 27606

University of North Carolina Highway Safety Research Center
730 MLK Jr Boulevard #300 Chapel Hill, NC 27599
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
DTFH61-13-D-0001
12. Sponsoring Agency Name and Address
Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101
13. Type of Report and Period Covered
Safety Evaluation; 2013–2016
14. Sponsoring Agency Code
HRDS-20
15. Supplementary Notes
The Federal Highway Administration (FHWA) Office of Safety Research and Development managed this study under the Development of Crash Modification Factors Program. The FHWA Office of Safety Research and Development program and Task Manager was Roya Amjadi (HRDS-20; ORCID: 0000-0001-7672-8485).
16. Abstract
This study evaluated the safety effect of the flashing yellow arrow (FYA) treatment at signalized intersections. The major objective of this strategy is to reduce the frequency of left-turn (LT) crashes, especially those that involve a collision between left turns and vehicles traveling straight through from the opposite direction. The project team conducted an empirical Bayes before-after analysis of installations in Nevada, North Carolina, Oklahoma, and Oregon. The treatments were divided into seven categories depending on the phasing system in the before and after periods, number of roads where FYAs were implemented, and number of legs at each intersection. The first five categories involved permissive or protected-permissive phasing in the before period. Intersections in these five treatment categories experienced a reduction in the primary target crashes under consideration: LT crashes and left-turn-with-opposing-through (LTOT) crashes at the intersection level. The reduction ranged from 15 to 50 percent depending on the treatment category. Intersections in categories 6 and 7 had at least one protected LT phase in the before period, and after phasing had an FYA protected-permissive LT phase without time-of-day operation (category 6) and with time-of-day operation (category 7). Consistent with results from previous studies, these intersections experienced an increase in LT and LTOT crashes. The B/C ratios for categories 1-5 ranged from 56:1 to 144:1.
17. Key Words
Intersection, flashing yellow arrow, phasing, low cost safety improvements, safety evaluations, empirical Bayesian, left-turn, left-turn opposite direction, crash modification function, crash modification factor
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
http://www.ntis.gov
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages
63
22. Price
N/A
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized.
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