In this paper, some commonly encountered issues are addressed that are related to video detection system applications at signalized intersections. Quantitative evaluations on the potential impact on intersection operations are provided. The issues addressed in the paper reflect various aspects of occlusion, a result of the parallax phenomenon in video detection systems. Occlusion in video detection systems can result in missed detections, false detections, and increased detector presence time, and thus may affect intersection operations under actuated control. Various models are developed to address these issues and quantitative evaluations are presented. It is found that missed detections due to occlusion of following vehicles are generally less than 10% when the approach volume is less than 600 vph. At this traffic volume level, additional phase extension time caused by occlusion is generally less than 4 seconds. To minimize false detections due to occlusion of adjacent lanes, the camera is better positioned to the division line between the lanes. It would require a much higher mounting position if the camera is located outside the travel lanes.
Abstract