A Special Application of a Video-image System for Vehicle Tracking and Speed Measurement

This paper documents a special application of a video-image system (AUTOSCOPE) to track main-street through movement vehicles and measure their individual speeds at two-way stop-controlled intersections. The initial objective of this application was to find an automated means to collect vehicle speeds at unsignalized intersections for the purpose of analyzing a driver’s gap-acceptance characteristics. To perform vehicle tracking for main-street through vehicles, a special application was developed which is beyond the basic system functions and features available in AUTOSCOPE. A vehicle-tracking program was developed that uses individual detector information and extracts the data associated with the mainstreet through vehicles. The study then addressed the issues that are related to speed measurement using video-image systems. Results from field tests indicated that the accuracy for tracking vehicle movements varies depending on the camera view. Under the worst-case scenario, the accuracy of vehicle tracking was about 87 percent. For speed measurements, the results were compared with those measured using a radar gun. The error was approximately ±5 km/h while reporting individual speeds. Although the speed data obtained from AUTOSCOPE may still lack the precision required for studies such as gap acceptance characteristics at unsignalized intersections, the method developed through this study showed good potential to develop special applications beyond the basic features and functions of video-image systems.