The use of video imaging vehicle detection systems (VIVDS) at signalized intersections in Texas has increased significantly due primarily to safety issues and costs. Installing non-intrusive detectors at intersections is almost always safer than installing inductive loops due to greater separation between passing motorists and field crews installing the detectors. Other factors that have contributed to the increased usage of VIVDS include the flexibility offered in terms of adjusting detection zones (e.g., with lane reassignments), the ability to send an image of the traffic stream to a traffic operations center, and no damage to the pavement structure as with inductive loops. Despite these advantages, there are situations where VIVDS need further research to ensure safe operations. The objective of this research is to determine how well the current video imaging systems deployed by the Texas Department of Transportation (TxDOT) provide dilemma zone protection at high-speed signalized intersections. Findings of this research indicate that VIVDS is better suited for stop line detection than dilemma zone detection. It will usually require two cameras and dedicated upstream poles to ensure adequate performance at speeds of 50 mph or higher. VIVDS has some inherent weaknesses that increase the number of max-outs and minor street delays compared to point detectors. (Author/publisher)
Abstract