Driver Comprehension of Flashing Yellow Arrows

Principal Investigator(s):

Gary Davis, Professor, Civil, Environmental and Geo-Engineering


  • John Hourdos, Former Research Associate Professor, Civil, Environmental and Geo-Engineering
  • Raphael Stern, Assistant Professor, Civil, Environmental and Geo-Engineering

Project summary:

In 2009, the Federal Highway Administration's Manual on Uniform Traffic Control Devices (MUTCD) introduced the flashing yellow arrow (FYA) traffic signal as an alternative to circular green (CG) to indicate permitted left turns. The FYA is arguably a more intuitive indication that left turns are permitted but not protected and, in addition, the FYA signal heads can support time-of-day changes between protective and permissive left-turn phasing. In 2019, a Research Needs Statement stated that, "Research is needed to examine driver comprehension of flashing yellow arrows in different light arrangements and the role of signage." The researchers' objective in this project was to assess drivers' understanding of FYA signal indications and to see if the presence or absence of "Left Turn Yield" signs affect gap acceptance. This was accomplished by conducting an online survey of drivers regarding their understanding of FYA signals and by carrying out a field study of drivers' gap acceptance at a set of Twin Cities intersections.

Project details:

Reports or Products: