Transcript Joel McCarroll—Flashing Yellow Arrows in Oregon (with video)

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
Before
LEFT TURN
YIELD
ON GREEN
After
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.
FYA Animation
Click to start animation
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
46 Cities with FYA in Oregon
Installation Details
• All ODOT installations had engineered signal
plans prepared.
• Evaluation of loading changes alleviated
structural concerns.
• Requires one more conductor than protectedonly 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
Custom Bracket for Spanwire Installations
Custom Bracket for Spanwire Installations
(Region 2 Electrical Crew Design)
Custom Bracket for Spanwire Installations
Other Issues
• Oregon has a few bi-modal heads.
• 20-7 Project to compare the approved 4
section head with a three section bimodal 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
([email protected])
Or
Gary Obery
([email protected])
Questions