Vision-Based Over-height Vehicle Detection

Over-height vehicle drivers continuously ignore warning signs and strike onto bridges despite the number of preventative methods installed at low clearance bridges. Asset owners are left to remedy the damages resulting in operation losses due to inspections, temporary road closures, and traffic delays. Intelligent transportation (IT) systems are needed that address all three key areas of over-height vehicle strike management: (1) prevention, (2) detection and, (3) reporting. In this paper the authors present a new method for over-height vehicle strike prevention using a camera, as a major improvement to the existing laser beam method. It replaces the transmitter, a receiver, and loop detectors with a single calibrated camera mounted on the side of the roadway. The camera is installed at the height of the “over-height plane” formed by the average of the maximum allowable heights across all lanes in a given traffic direction. At that height, the over-height plane can be safely approximated as a line in the camera view. Any vehicle exceeding this line is consequently over-height. The camera position and orientation is determined via a calibration process proposed. Instances of over-height vehicles are detected via optical flow monitoring. A total station was used to collect ground truth data for validating the height accuracy. Evaluation of the system yielded a height accuracy of ±2.375 mm and detection accuracy of 99.9 %. While its accuracy is comparable to existing laser beam systems, it outperforms them on cost which is an order of magnitude less due to eliminating the need for new permanent infrastructure.