Study Admits Yellow Times Too Short at IntersectionsTransportation officials recommend adding 0.5 seconds of yellow time in new report.
Nov. 06, 2012
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A report by state transportation officials released last week tacitly admitted drivers are being shortchanged when the light at an intersection turns yellow. The National Cooperative Highway Research Program (NCHRP) released its guidelines on how municipalities can best time their signals for safety. The net result is that most intersections would see yellows extended by roughly half-a-second if the recommendations were adopted.
Signal timing has become a highly political issue due to lobbying by the National Motorists Association and the 2001 release of a report on the issue by the US House Majority Leader (view report). Various changes to the signal timing formula and other techniques have been used so that yellows are roughly one second shorter in the current Institute of Transportation Engineers (ITE) formula compared to what the prior formula used in 1976 generated. The states of Ohio and Georgia responded in the past three years by enacting laws mandating an extra second of yellow, resulting in a documented reduction in red light running. The NCHRP report admits the benefit of longer yellows.
"Increasing the yellow change interval to the duration calculated by current ITE guidelines has been shown to reduce red-light running occurrences between 36 and 50 percent," the report explained.