Characterization of glass beads by image methods for pavement marking retroreflectivity

Road safety is a worldwide concern. Traffic injuries are the main cause of death for children and young people. One alternative to improve traffic safety is the enhancement of pavement markings visibility. Pavement marking efficiency depends on day and night visibility. Nighttime visibility (retroreflectivity) occurs due to the presence of glass beads. This paper compares the performance of two glass beads: G1 – Brazilian glass bead produced with recycled glass; and G2 – imported glass bead produced with new material. The research evaluated the retroreflectivity decrease of a test deck using two water-based paints from different manufacturers. The glass beads characterization process used the Computerized Optical Equipment (COE), CamSizer, and the Aggregate Image Measurement System (AIMS) to evaluate the shape, size, and gradation. Results indicated different retroreflectivity decrease trends for pavement markings with distinct glass beads, which could be associated with their shape characteristics and grain size distribution. The glass beads G1 presented the worst shape properties which lead to the poorest retroreflectivity at the test site. Thus, image characterization is helpful in estimating markings retroreflectivity prior to its application. Therefore, G1 cannot be used to substitute G2, regarding the retroreflectivity requirements in Brazil.