Use of Digital Imaging Methods to Assess Pavement Marking Retroreflectivity

This study explores the application of two-dimensional digital image processing and video imagery analysis as methods to estimate pavement marking retroreflectivity. A sample of white, waterborne paint pavement markings were applied on an asphalt pavement at an outdoor test and the application process was recorded using a high-speed video camera attached to the paint truck. Several glass bead kinematic descriptors were collected during this process, and it was found that the true impact angle and the horizontal and vertical components of the bead speed were associated with pavement marking retroreflectivity. Sample test plates of the pavement markings were prepared during the application process. These samples were weathered for one year and subjected to more than one million accelerated traffic passes. The percentage of glass beads covering the sample tests plates were assessed using a digital image processing algorithm and compared to the retroreflectivity measured on the markings applied to the test track. It was found that bead coverage was associated with pavement marking retroreflectivity in the weathering and accelerated wear tests. Collectively, the high-speed video and two-dimensional image processing methods appear to offer laboratory tests to evaluate pavement marking durability and visibility.