Presentation on theme: "Flashing Yellow Arrows Joel McCarroll, Region 4 Traffic Manager on behalf of Edward L. Fischer State Traffic Engineer Oregon Department of Transportation."— Presentation transcript:
Flashing Yellow Arrows Joel McCarroll, Region 4 Traffic Manager on behalf of Edward L. Fischer State Traffic Engineer Oregon Department of Transportation
History of Flashing Yellow Arrows NCHRP 493 (2003) Evaluation of Traffic Signal Displays for Protected/Permissive Left Turn Control FHWA Interim Approval for Optional Use of Flashing Yellow Arrow for Permissive Left Turns (March 2006) NCHRP Web-Only Document 123 (2007) Evaluation of FYA
Background Concerns with permissive circular green. Concern with circular green in doghouse. NCHRP 493 studied a wide variety of potential displays. Study included driver comprehension studies, video conflict studies, and crash analyses.
Traditional Five-Section “Doghouse” Courtesy of ODOT Photo and Video Services
Intersection with a FYA Head Courtesy of ODOT Photo and Video Services
Flashing Yellow Arrow Head Courtesy of ODOT Photo and Video Services
Comparison of Conversions LEFT TURN YIELD ON GREEN BeforeAfter
FYA Head Configuration Separate signal face for the left turn signal face. Standard FYA head has four sections, all arrows. A three-section signal face with bimodal section (green arrow and yellow flashing arrow) may be used where impractical to use four-section head.
Meaning of Indications The steady red, yellow and green indications have the usual meanings –Steady Red Arrow means stop –Steady Green Arrow means protected turn –Steady Yellow Arrow means the phase is changing The flashing yellow allows you to turn left when oncoming traffic is clear (oncoming traffic has a green light).
Summary of Research NCHRP 493 found that displays with exclusive heads were found to offer the higher ratings in terms of safety, operations, human factors, and versatility. The FYA was found to be more intuitive and had fewer “false positive” reactions as compared to the green ball. NCHRP Web-Only Document 123 follow-up study indicated significant safety benefits of the FYA.
Crash Reductions Found in NCHRP 123 12 intersections studied (3 in Oregon) –Conversions from doghouses to FYA’s –Limited before/after data sets 74 percent reduction in left-turn related crashes.
Benefits of FYA High level of understanding Best overall alternative to circular green More versatility in field operation –Lead/lag and left turn re-service –Time of day flexibility to run protected only, PPLT, or permissive only.
Implementation Oregon, Florida, and Maryland were among the first few states with the FYA under the FHWA Experimental status. After FHWA Interim Approval, many other jurisdictions across the country are now using the FYA. Draft MUTCD includes the FYA.
ODOT Evaluation of FYA Data available for 5 conversions from Doghouses to FYA before 2008 Annual average left-turn-related crashes reduced from 1.1 crashes/yr/intersection to 0.35. (Reduction of 67%) Calculated Benefit/Cost Ratio from crash reductions is approximately 8:1 More comparable crash data will be available starting in 2010. (30 recent conversions from Doghouse to FYA).
Operation of FYA’s in Oregon Delay of Flashing Yellow Arrow allows opposing traffic to get started while the FYA head remains red. (~3 seconds) Minimum 3 second red indication during transition from protected to permissive operation. Seems to be some reluctance among signal timers to run coordinated lead/lag operation.
FYA Operation Courtesy of ODOT Photo and Video Services
FYA’s in Oregon Flashing Yellow Arrow is the ODOT standard for Protected/Permissive Phasing. We are systematically replacing doghouses with FYA. We are about 1/3 complete. 49 installations on ODOT highways 183 installations on city streets and/or county roads 46 cities now have at least one FYA within their city limits
Installation Details All ODOT installations had engineered signal plans prepared. Evaluation of loading changes alleviated structural concerns. Requires one more conductor than protected- only head. FYA monitored through conflict monitor. All 30 conversions in 2008/2009 were completed by ODOT electrical crews
Signal Timing ODOT currently using Wapiti’s W4IKS, W4HC11, or Voyage W4IKS requires command-box logic of approximately 200 lines of code. Necessitates use of laptop to download timing to controller. W4HC11 has new tables for FYA without command box. Voyage software for the 2070L controller runs the FYA without command box.
Costs of Conversion 30 intersections were converted from doghouse left turn heads to the FYA head. Most conversions involved 2 doghouse heads Average cost was $9,100 per intersection including: –Site assessment and engineering –Hardware –Installation labor –Temporary traffic control
Other Issues Oregon has a few bi-modal heads. 20-7 Project to compare the approved 4 section head with a three section bi- modal head. Jackson County in southern Oregon has experimental approval for FYA’s that operate differently from the interim approval.
Summary In Oregon, the FYA has proven to be: Significant safety improvement over the doghouse Easily understood by drivers Versatile Easy to install, operate, maintain Popular in many jurisdictions
More Information Contact Ed Fischer (Ed.L.Fischer@odot.state.or.us)Ed.L.Fischer@odot.state.or.us Or Gary Obery (Gary.R.Obery@odot.state.or.us)Gary.R.Obery@odot.state.or.us