Abstract
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.