Safety Evaluation of Flashing Yellow Left-Turn Arrows in Missouri

The Missouri Department of Transportation (MoDOT) has been utilizing flashing yellow arrows for left turns on state routes since 2006 after receiving interim approval from the Federal Highway Administration (FHWA). MoDOT has been installing these signal indications at new signalized intersections where a permissive left turn is needed and updating current locations with a circular green ball for permissive movements to the flashing yellow arrow across the state. For various reasons, there have been questions whether the change to the flashing yellow arrow for left turns has actually led to an increase in crashes over recent years. Given that there is sufficient crash data at this point, this project will provide a valuable Missouri-focused study on the before and after safety of flashing yellow left-turn arrows for left turns.