Impact of Detection Zone Length on Continuous-Wide-Area (CWA) Detector-Based Dilemma Zone Protection at Rural High-Speed Signalized Intersections

Continuous Wide Area (CWA) detectors are increasingly favored over traditional point detectors due to their cost-effectiveness, ease of installation, and advanced detection capabilities. A critical aspect of implementing CWA detectors is determining the appropriate detection zone coverage to ensure effective dilemma zone protection (DZP) and improved traffic signal operations. Despite the growing adoption, existing research provides limited guidance on methodologies for determining the most suitable detection zone length or assessing its impact on traffic operation. Focusing exclusively on rural high-speed signalized intersections, this study addresses the existing gap by examining the effect of varying detection zone lengths on intersection performance at two sites equipped with CWA detectors for DZP. Detailed traffic data were collected to develop multiple DZP scenarios with varying detection zone lengths in simulation. These scenarios were evaluated using key performance measures, including vehicle arrivals, intersection delay, phase max-out frequency, and queue length. Results showed that superior operational benefits can be achieved by setting detection zones longer than Type-II dilemma zone lengths. Longer detection zones increased the green time allocated for major roads, resulting in higher green arrivals and lower yellow/red arrivals. However, this also increased minor road delays and major road phase max-outs, potentially diminishing DZP benefits. The findings indicate that a well-balanced detection zone length is primarily influenced by traffic volume, time‑of‑day variability, turning‑movement distribution, and the geometric characteristics of the intersection. The site-specific simulation framework employed in this study provides a practical basis for identifying detection zone lengths that balance operational trade-offs while ensuring safety.