A spreadsheet tool designed to help MnDOT and other agencies determine where and when it’s safe to use flashing yellow arrows is now available on the Minnesota Local Road Research Board website.
Flashing yellow arrows warn drivers that they can make a left turn only after yielding to any oncoming traffic or pedestrians. These signals can help prevent crashes, move more traffic through an intersection, and provide additional traffic management flexibility. Many transportation agencies are interested in using flashing yellow arrows to accommodate within-day changes: protected left turns (signaled by a green arrow) could be used when needed to lower crash risk, while permitted left turns (signaled by a flashing yellow arrow) could be used to reduce delay when crash risk is low.
The spreadsheet tool helps traffic engineers determine when the crash risk at an intersection is sufficiently low to allow flashing yellow arrows to be implemented safely. Using the tool, engineers can choose their type of intersection and enter the available turning movement count. The tool then generates a specialized graph for that intersection showing the relative crash risk by time of day. Any time the crash risk is at or below the level identified as acceptable, engineers can consider using flashing yellow arrows.
The tool was developed as part of a project led by Gary Davis, a professor in the Department of Civil, Environmental, and Geo- Engineering at the U of M.
- Download the spreadsheet tool
- Download the tool instructions
- Read a January 2015 Catalyst article about the project
- Read the project final report