NCHRP Report 731: Guidelines for Timing Yellow and All-Red Intervals at Signalized Inter-sections provides comprehensive and uniform guidelines for safe and efficient yellow change and all-red clearance intervals at signalized intersections. These proposed guidelines pro-vide a framework that can be easily applied by state and local transportation agencies. This report will be of interest to safety and traffic engineers. Red-light running is one of the most common causes of intersection crashes. Yellow and all-red 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. The generally accepted definition of the yellow change interval is that it is a warning to 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. 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. Under NCHRP Project 03-95, Vanasse Hangen Brustlin, Inc., undertook the development of a comprehensive and uniform set of proposed guidelines for determining safe and operationally efficient yellow change and all-red clearance intervals at signalized intersections. Initially they (1) reviewed and compared the definitions of yellow change and all-red clearance intervals, (2) conducted a critical review of relevant available literature, (3) conducted a survey of yellow and all-red timing practices at public agencies, and (4) reviewed past studies and agency operational experiences in relating change interval timing to red-light running and crashes. This information was synthesized to identify key stakeholder groups, point out knowledge gaps encountered in the research, and produce a draft outline of the guidelines. Field studies were conducted on critical factors including reaction time, deceleration rates, and the impact of the other factors identified as important in the design of change intervals. This information was analysed to develop draft yellow change and all-red clearance interval guidelines, which were submitted to NCHRP and the key stakeholder groups for review and comment. Comments were addressed to produce a final report to document the research effort and the stand-alone, proposed guidelines for timing yellow and all-red intervals. (Author/publisher)
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