Effectiveness of Alternative Detector Configurations for Option Zone Protection on High-Speed Approaches to Traffic Signals

Abstract

Safety and efficiency are both prime issues of concern at high-speed isolated signalized intersections. However, although safety problems at such intersections can be mitigated by the application of detector configurations with option zone (also called decision zone) protection, such configurations can themselves create problems. Although option zones are often called dilemma zones, the term “dilemma” is reserved for issues associated with yellow and red clearance intervals. In this study, four detector configurations for option zone protection features—the single-detector configuration, the Southern District Institute of Traffic Engineers configuration, the Beirele configuration, and the Bonneson configuration—are compared through computer simulation for their effects relative to the number of vehicles in the option zone, max-out occurrences, and average vehicle delay. The comparison suggests that although each configuration has its own advantages and disadvantages, the Bonneson detector configuration, in most circumstances, yields the lower number of vehicles in the option zone per cycle and less average delay.