A Field and Simulator Evaluation of All-Red Clearance Intervals for Use in Left-Turn Applications

As the implementation of the novel flashing yellow arrow (FYA) traffic control device advances throughout the country, agencies continually seek ways to improve intersection operations and safety, especially on left turns. For example, permissive left-turn intervals have been communicated to drivers using several traffic signal indications; however, most frequently these phases are represented using the circular green ball and, more recently, the FYA. Previous research in this area found that the FYA indication produced the most effective communication of permissive left-turns. As a result of the research findings, the FYA was included in the 2009 edition of the Manual on Uniform Traffic Control Devices. In recent years, agencies across the country have embraced the implementation of the FYA for permissive left-turns. However, a lack of national guidance remains on how to define the change and clearance intervals for transitioning between protected and permissive left turns. Complicating the matter is the connection between traditional signal phasing/design and human factors. Research on driver comprehension and real-world operations of the transition between protected and permissive left turns will allow evaluation not only of current conditions, but also of experimental and future conditions. This report presents findings from a static survey that studied the expectation of drivers after a signal indication is presented. This report also presents the results of a novel exploratory approach that allows the use of vehicle trajectory data to gain an insight into driver behavior during the transition between a protected left-turn movement and a permissive one. Research findings will provide a foundation for narrowing the scope and identifying elements that should be considered during a driving simulator evaluation.

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  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    Safety Research Using Simulation University Transportation Center (SaferSim)

    University of Iowa
    Iowa City, IA  United States  52242

    University of Massachusetts, Amherst

    Department of Civil and Environmental Engineering
    130 Natural Resources Road
    Amherst, MA  United States  01003

    University of Wisconsin, Madison

    Department of Civil and Environmental Engineering
    1415 Engineering Drive
    Madison, WI  United States  53706

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Authors:
    • Knodler Jr, Michael A
    • Christofa, Eleni
    • Tainter, Francis
    • Santiago-Chaparro, Kelvin R
    • Bill, Andrea R
    • Noyce, David A
  • Publication Date: 2018-3


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 47p

Subject/Index Terms

Filing Info

  • Accession Number: 01673356
  • Record Type: Publication
  • Created Date: Jun 11 2018 9:58AM