Automatic identification of cracks in road surfaces

The Highways Agency required a high speed automatic crack monitoring system capable of identifying and locating surface cracks of widths of approximately 2 mm and greater, over at least 80% of the width of a traffic lane (the width of traffic lanes on motorways and all-purpose trunk roads ranges approximately between 3 m and 3.65 m). Transport Research Laboratory Ltd., assisted by Softronic Systems Ltd, has undertaken an extensive programme of research, to develop an automatic crack monitoring system. The developed system now forms part of the Highways Agency Road Research Information System (HARRIS). In HARRIS, images of the road surface are collected by the survey vehicle and automatic processing of these images is then carried out in two stages. The first, or primary, stage of processing, to clean and reduce the images, is carried out in real time on board the vehicle during the survey. The second stage, that of processing the reduced images for the identification of cracks, is carried out off-line on Pentium II PCs, which are installed on the survey vehicle.