DESIGN, DEPLOYMENT, AND EVALUATION OF AN INTEGRATED DILEMMA ZONE PROTECTION SYSTEM FOR IMPROVING SAFETY AND MOBILITY FOR HIGH SPEED SUBURBAN INTERSECTIONS
PARK, SUNG YOON
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Despite the fact that both traffic researchers and highway agencies have devoted considerable efforts over the past few decades on improving intersection safety, development of effective strategies to contend with this vital issue remains a challenging task. This dissertation presents the design, deployment, and evaluation of a dilemma zone protection system (DZPS) to cope with the safety issues due to the presence of a dilemma zone, a primary factor contributing to rear-end collisions or side-angle traffic crashes, especially at suburban intersections with high-speed traffic flows. The DZPS provides safety improvements from both proactive and reactive perspectives. It also features a dynamic function for speed harmonization with minimal additional hardware to fully utilize each key component for safety and mobility improvements. The dissertation consists of four parts; the first part illustrates the development of a simulation platform, including step-by-step procedures and details on how all embedded algorithms have been integrated and implemented for pre-deployment analysis. Recognizing that a reliable evaluation of a deployed DZPS’s effectiveness requires observation of field data collected over a long time period, the developed simulator will serve the need of identifying potential control and operation issues prior to field deployment with well-calibrated simulation experiments. The second part highlights the DZPS’s embedded algorithm for all-red extension, which has been developed to provide additional clearance time to red-light-running vehicles so as to prevent crashes with side-street vehicles. The third part of this study focuses on the design of a speed harmonization module with a variable speed sign using existing hardware for executing the all-red extension. The enhanced system offers additional functions for predicting gap-out timing and calculating the advisory speed for approaching vehicles during the green phase to progress through the intersection. The last part of this research focuses on conducting a field evaluation for the deployed DZPS. The results of extensive analysis show that the system is effective in reducing both the average speed of approaching vehicles and the spatial range of dilemma zones. Most importantly, the developed system can indeed offer full protection to prevent drivers from becoming trapped in a dilemma zone and causing angle-crashes, as expected, at the acceptable preset rate of false alarm.