The organization that led the charge for lowering yellow times around the nation decades ago conceded Monday that it may have gone too far. The Institute of Traffic Engineers (ITE) released formal guidelines lengthening the yellow warning times for left-turn lanes at intersections to as long as seven full seconds.
“ITE has concluded a years-long effort to issue guidance on yellow change and red clearance intervals for signalized intersections,” ITE senior director Doug Noble wrote in the organization’s March journal. “This report is not intended to cover specific enforcement actions to address red light running, but does acknowledge that the range of values for variables used in calculating change intervals and the range of driver behavior they represent makes zero tolerance enforcement inappropriate.”
A motorist approaching an intersection that is about to display a red light needs enough warning from the yellow light to either come to a safe stop, or to proceed safely through the intersection. Yellows that are overly short can create what is called a ‘dilemma zone’ in which there is not enough time to stop safely, and there is no way to get through the intersection without running the red light.
The new ITE guidelines are based on an “extended” equation that for the first time takes into account the extra time needed when turning. The change was spurred by the research of Oregon engineer Mats Jarlstrom, Safer Streets LA executive director Jay Beeber, North Carolina professional engineer Brian Ceccarelli, and the National Motorists Association‘s professional engineer Joe Bahen. In addition to making their point mathematically, the group set up a real-life demonstration that proved the previous ITE recommendation tended to create dilemma zones for drivers making turns. ITE acknowledged that more change might be needed, if justified by the facts.