This report summarizes the investigation of whether intelligent advanced warnings of the end of green signal helps drivers negotiate the dilemma zone (DZ) at signalized intersections and identifies behavioral mechanisms for any warning related benefits. Prior research suggested that warnings of end of green can increase slowing and stopping frequency given the dilemma zone, but drivers may sometimes respond to warnings by speeding up. In two simulator studies, six types of roadway or in-vehicle warnings were compared with a no-warning control condition. Using multi-level modeling, mediation models of the behavioral mechanisms underlying the effects of the warnings were tested.
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