Recasting Dilemma Zone Design as a Marginal Cost-Benefit Problem

Dilemma Zone Design as a Marginal Cost-Benefit Problem" (2007). One control objective at high-speed isolated intersections is to provide safe phase transition by minimizing the occurrence of high-speed vehicles in the dilemma zone before the phase is terminated. An upper limit for extending the green (maximum green time) is used to avoid an indefinite extension of the main-street green. Currently, the maximum green times are chosen by using engineering judgment. This approach does not explicitly consider the trade-offs between safety and delay and hence often results in both unsafe and inefficient performance at the intersection under medium to heavy traffic volumes. The dilemma problem is recast as one of minimizing the number of vehicles entering the upstream decision conflict zone (DCZ). An economic evaluation approach is proposed to maximize both safety and efficiency at the intersection by considering the problem in terms of marginal costs and benefits.Traf-fic conflicts are used to estimate potential safety benefits, and the induced delay cost is used to estimate the cost accrued on side-street traffic that is associated with extending a competing phase. This approach allows the implementation of logic that minimizes DCZ exposure instead of the current approach of absolute protection until the maximum green time is reached, at which time no consideration is given to dilemma zone exposure when the phase is terminated. This approach handles efficiently and safely the periods of moderate demand volumes when current dilemma zone protection frequently encounters maximum green time exposure. The National Safety Council (1) reported motor vehicle crashes as the leading cause of unintentional injury deaths in the United States for 2003. A death is caused by a motor vehicle crash every 12 minutes and a disabling injury occurs every 13 seconds. The cost of motor vehicle collisions in 2005 through April to-taled nearly $70.8 billion (2). Intersection crashes constitute 30% of all vehicle crashes (3); they account for an average of 9,000 fatalities and 1.5 million injuries annually. Red light running (RLR) is a major cause of fatal and injury-related crashes. Also, motorists are more likely to be injured in such crashes. A survey conducted by the U.S. Department of Transportation and the American Trauma Society indicates that 63% of Amer-icans witness an RLR incident more than once a week and one in three Americans knows someone who has been injured or killed because of a red light violation. Green extension systems are deployed at …