Safety and Operational Impacts of Optional Flashing Yellow Arrow Delay

Abstract

Considerable debate exists over whether to delay the start of the flashing yellow arrow (FYA) signal indication (e.g., with a red arrow signal indication) during the transition from a protected movement to a permissive movement in a leading left protected–permissive left turn. The 2009 Manual on Uniform Traffic Control Devices is silent on this topic. This paper reviews the state of the practice on the use of the optional FYA delay through a literature review, a survey of state departments of transportation, and consultations with practitioners and national experts. A simulation study was also used to assess the potential impacts of the optional FYA delay on traffic safety and operations. The state-of-the-practice review indicated some preference for the use of the red arrow signal indication because of the perceived safety benefit. For example, 71% of the responding state departments of transportation that use the FYA also delayed the start of the FYA. The simulation analysis showed significant safety benefits in a delay to the start of the FYA signal indication for all scenarios except the scenario with a low opposing through traffic volume, with no significant negative impacts on average delay, average queue length, or average stopped delay for either left-turning traffic or the intersection as a whole being found.