Flashing yellow arrow indicators have been deployed at many signalized intersections in recent years to control left-turn movements and improve traffic flow.
When illuminated, the flashing yellow arrow allows waiting motorists to make a left-hand turn after yielding to oncoming traffic.
The Federal Highway Administration considers flashing yellow arrows to be a significant safety improvement over traditional yield-on-green indicators, which are believed to be less intuitive. However, motorist complaints and some high-profile crashes indicate that there is still some level of driver confusion.
Some Minnesota agencies have installed or continue to receive requests, even years after implementation, for “LEFT TURN YIELD ON FLASHING YELLOW ARROW” signs to clarify the operations.
A new Minnesota research study intends explore methods to improve driver comprehension of flashing yellow arrow signals and develop further guidance for their appropriate implementation. Researchers will survey drivers about their comprehension of different signal indications and conduct a field study to monitor driver behavior when facing different signal indications. Factors to be considered include sight distance and opposing vehicle speeds.
While research suggests that drivers generally appear to understand that Flashing Yellow Arrows indicate a permitted, but not protected, left-turn, confusion may be occurring due to time-of-day switches from protective to permissive phasing. (How to best transition from protective to permissive phasing is the current aim of National Cooperative Highway Research Program (NCHRP) Project 3-125.)
Another complication could be the various light arrangements (e.g., vertical stack or 5-light cluster) used by some agencies.
- Estimated Start Date: 07/22/2020
- Estimated Completion Date: 06/30/2022
- Funding: Local Road Research Board
- Principal Investigator: Gary Davis
- Technical Liaison: Victor Lund
Details of the research study work plan and timeline are subject to change.
To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.