U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-19-036 Date: August 2020 |
Publication Number: FHWA-HRT-19-036 Date: August 2020 |
PDF Version (1 MB)
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
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| 1. Report No. FHWA-HRT-19-036 |
2. Government Accession No. | 3. Recipient’s Catalog No. | ||||
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| 4. Title and Subtitle Safety Evaluation of Flashing Yellow Arrow at Signalized Intersections |
5. Report Date August 2020 |
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| 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 |
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| 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 |
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| 14. Sponsoring Agency Code HRDS-20 |
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| 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). |
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| 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. |
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| 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 |
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| 19. Security Classif. (of this report) Unclassified |
20. Security Classif. (of this page) Unclassified |
21. No. of Pages 63 |
22. Price N/A |
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| Form DOT F 1700.7 (8-72) | Reproduction of completed pages authorized. | |||||
