Evaluation of the Flashing Yellow Arrow Permissive-Only Left-Turn Indication Field Implementation

The primary objective of this research was to evaluate the safety of the flashing yellow arrow (FYA) permissive only left-turn indication field installations. The ability of the FYA indication to improve safety was evaluated with respect to crash experience. Findings of the crash analysis were interpreted with respect to other variables such as signal phasing, vehicle flow rates, posted speed limits, and intersection geometry. The scope of this research included all known installations of the FYA prior to the commencement of this research. Data were limited to that which was made available by traffic engineers in locations where the FYA has been implemented, along with selected data that were directly obtained by the researchers. Findings were drawn from the analysis of 50 intersections in which the left-turn FYA indication was installed. Safety was improved at intersections that operated with protected/permissive left-turn (PPLT) phasing prior to field implementation of the FYA permissive only indication. Safety was not improved at intersections that operated with protected only left-turn phasing prior to field implementation of the FYA indication with PPLT phasing. The change in signal phasing had a more significant impact on safety than the change in permissive indication. No conclusions could be made at intersections that operated with permissive only left-turn phasing prior to implementation of the FYA indication, due to a minimal number of implementation sites and data. The results showed that the installation of the FYA indication for permissive left-turns provided a safety improvement when added to existing PPLT signal phasing operations.


  • English

Media Info

  • Media Type: Web
  • Edition: contractor Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 146p
  • Serial:
  • Publication flags:

    Open Access (libre)

Subject/Index Terms

Filing Info

  • Accession Number: 01100741
  • Record Type: Publication
  • Report/Paper Numbers: NCHRP Project 20-7/Task 222
  • Files: TRIS, TRB, ATRI
  • Created Date: Jun 6 2008 2:18PM