Red-light running is one of the most common causes of intersection crashes. The generally accepted definition of the yellow change interval is to warn motorists that the related green movement is being terminated or that a red signal indication will be exhibited immediately thereafter. Some jurisdictions supplement the yellow interval with an all-red interval to provide additional clearance time. Interval duration is a significant factor affecting the frequency of red-light running, yet there remains no national consensus on how the yellow and all-red intervals should be timed for safe and efficient operations. Studies of driver reaction times and vehicle deceleration rates used in determining appropriate yellow and all-red change intervals were conducted more than 25 years ago. Additional research was needed to consider other factors that may be important in designing change intervals including speeds, grades, vehicle types, vehicle mix, road surface conditions, sight distances, geometric considerations, coordinated systems and isolated signals, signal timing parameters, advanced detector locations, driver age, and turning movements.  The objective of this project was to develop a comprehensive and uniform set of recommended guidelines for determining safe and operationally efficient yellow and all-red intervals at signalized intersections.

NCHRP Report 731: Guidelines for Timing Yellow and All-Red Intervals at Signalized Intersections, is located here.

NCHRP Project 03-95: Guidelines for Timing Yellow and All-Red Intervals at Signalized Intersections complete contractor's final report is here.