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The National Academies

NCHRP 20-07/Task 283 [Final]

Evaluation of the Flashing Yellow Arrow (FYA) Permissive Left Turn in Shared Yellow Signal Sections
[ NCHRP 20-07 (Research for AASHTO Standing Committee on Highways) ]

  Project Data
Funds: $99,995
Research Agency: University of Wisconsin-Madison
Principal Investigator: David Noyce
Effective Date: 8/3/2012
Completion Date: 6/2/2014

OBJECTIVE
The objective of this research was to explore the effectiveness of a three section protected/permissive left turn signal display versus a four section signal display, containing both a flashing yellow arrow section and a steady yellow arrow change interval section, when implementing the FYA in protected/permissive left turn control.

STATUS

NCHRP Web-Only Document 207: Evaluation of the Flashing Yellow Arrow (FYA) Permissive Left-Turn in Shared Yellow Signal Sections has been published. The contractor's final report is available at the link below. The FHWA has issued interim approval that permits the optional use of a FYA in a three-section traffic signal head. Additional details are available at https://ops.fhwa.dot.gov/resources/news/news_detail.asp?ID=932

TASKS
Task 1.  Literature Review
Task 2.  Static and Dynamic Reviews: Licensed drivers will be recruited for computer-based static evaluations and simulator test to determine how well they understand and react to different displays of the flashing yellow arrow and change interval indications.

Task 3.  Field Assessment: The research team will evaluate real-world applications of the three and four section heads for PPLT. Data will be presented in a case study format.

Task 4.  Experimental Results and Data Analysis: Statistically analyze results from the static and dynamic reviews.

Task 5.  Draft Final Report and Final Report 

 

BACKGROUND

It is possible to operate the flashing yellow arrow in PPLT in existing three section heads by installing a bi-modal head that allows the yellow left turn arrow to operate in flashing (permissive) and steady (change) mode. It is not known how well drivers will respond to this application of the three section head and whether it provides adequate notice that the permissive left-turn is ending.

The National Cooperative Highway Research Program (NCHRP) project 3-54 (Evaluation of Traffic Signal Displays for Protected/Permissive Left Turn Control) recommended the use of the Flashing Yellow Arrow as the desired permissive indication for when using protected/permissive left turn (PPLT) phasing. The recommended display for the PPLT is a four section head. However, there are occasions where installing a four-section head can be very expensive or impossible without significant retrofit because of vertical clearance issues.

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