Date of this Version
Transportation Research Part B (2012) 46: 1,404-1,418.
This study seeks to identify the optimal location of an advance point traffic detector (APTD) to support green termination algorithms for enhanced dilemma zone protection systems at high-speed isolated signalized rural intersections. This is done by developing a nonlinear optimization model with the objective to maximize the opportunities to predict empty dilemma zones during a look-ahead time period subject to the prediction accuracy which is manifested through prediction efficiency and safety constraints in the model. The distance of the APTD from the stop bar of the intersection represents the decision variable. The Golden-Section line search algorithm combined with numerical integration techniques is proposed to identify the feasible region and the optimal solution. The proposed methodology is analyzed using field data from a high-speed isolated intersection in Lincoln, Nebraska. The numerical experiments demonstrate that as the constraints associated with prediction efficiency and safety are relaxed, the feasible range to deploy the APTD increases. The optimal solution is influenced by the relationship between the prediction error and the location of the APTD, illustrating the need to robustly calibrate the function used to estimate the variance of the prediction error using field data. From a practice standpoint, the study confirms the potential concerns related to the performance efficiency of green termination systems using a point detector; typical field implementations locate the detector 750 ft - 1,000 ft from the stop bar, which can potentially lead to significant levels of missed opportunities to terminate green safely. Overall, the proposed approach not only provides a systematic analytical methodology to determine the optimal location of the advance detector, but also to identify its feasible range based on user-specified thresholds related to efficiency and safety.