Evaluation of Change and Clearance Intervals Prior to the Flashing Yellow Arrow Permissive Left-Turn Indication

The flashing yellow arrow has been the focus of many research efforts over the past 20 years. Those efforts culminated with the inclusion of the flashing yellow arrow (FYA) as a permissive left-turn and right-turn indication in the 2009 Manual on Uniform Traffic Control Devices (MUTCD). As such, implementation of FYA indication operations across the country has rapidly increased. As an example, Washington County, Oregon, added the FYA permissive left-turn indication to over 300 signalized intersections in a single year. Other cities and states have also installed hundreds of FYA indications. One of the issues with the implementation of the FYA indication that has not been effectively addressed by research is the indication sequence prior to and immediately after the FYA indication that most effectively communicates the desired action to road users. For example, many jurisdictions who have implemented the FYA permissive left-turn indication, following a green arrow protected left-turn indication, use both the yellow arrow change indication and the red arrow clearance indication prior to initiating the FYA indication. Although not currently required by the MUTCD, some traffic engineers believe that the solid red arrow is needed to effectively communicate to drivers that the left-turn movement has switch from protected to permissive. Other traffic engineers allow the solid yellow arrow change interval following the protected left-turn movement to immediately change to the FYA indication, without the use of the solid red arrow clearance indication. The need for the red arrow clearance indication, its effectiveness when used, and the appropriate duration for its use have not been explored. Traffic engineers lack the necessary guidance in using the sold red arrow prior to the FYA indication. Research is needed to determine the need and best methods of using the solid red arrow clearance indication when the FYA indication is used. The objective of this research is to better understand the safety and efficiency implications of the use of solid yellow arrow change and solid red arrow clearance intervals after a leading solid green arrow transitioning to a permissive FYA or after a permissive FYA transitioning to a lagging solid green arrow. Specifically, there is a need to understand what intersection characteristics result in a value proposition that supports the use of both the solid yellow arrow change and solid red arrow clearance intervals. Additionally, there is a need to determine the appropriate duration of the red clearance interval when it is used. The influence of opposing bicycle, pedestrian and vehicle volumes and gaps, left turning demand, approach speeds, and lane configurations will all be considered. Ultimately, recommendations for the inclusion of change and clearance intervals and their correct durations will be drafted in a form as to be considered for inclusion in updates to documents such as the MUTCD or the Traffic Signal Timing Manual.


  • English


  • Status: Proposed
  • Funding: $300000.00
  • Contract Numbers:

    Project 03-125

  • Sponsor Organizations:

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway & Transportation Officials (AASHTO)

    444 North Capitol Street, NW, Suite 225
    Washington, DC  United States  20001

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Derr, B

  • Start Date: 20150626
  • Expected Completion Date: 0
  • Actual Completion Date: 0
  • Source Data: RiP Project 39946

Subject/Index Terms

Filing Info

  • Accession Number: 01568389
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 03-125
  • Files: TRB, RiP
  • Created Date: Jun 27 2015 1:00AM